Intrauterine growth restriction - and a postulated treatment modality for clinical research and it's biochemical rationale

[0001] In both developed and developing countries, infant birth weight is probably the single most important factor affecting the neonatal mortality and morbidity. Gruenwald (1963) reported that approximately one third of the low birth weight infants were mature and that their small size can be explained by chronic fetal distress, probably due to placental insufficiency. These and observations by many other led to development of the concept that the birth weight was governed not only by the length of gestation but also by the rate of fetal growth.

[0002] Definition—Small-for-gestational age (SGA) infants are those whose weights are below the 10th percentile for their gestational age. Thus approximately 10% of human births are deemed ‘small’ and these were shown to be at increased risk for neonatal death.

[0003] Usher and McLean (1969) proposed that fetal growth standards should be based on mean values with normal limits defined by plus or minus 2 standard deviations and this definition restricts small for gestational age infants to 3%, compared to 10% when percentiles were used.

[0004] Etiology—A variety of conditions starting from infections to congenital anamolies are known to cause intrauterine growth restriction (IUGR). 25-30% will have suffered from uteroplacental insufficiency of various causes and this is the clinical situation we are interested in this present clinical discussion. Chronic vascular disease especially when it is further complicated by superimposed preeclampsia, commonly cause growth restriction. Conversely preganancy induced hypertension, with out under lying vascular and renal disease, is unlikely to be accompanied by preeclampsia.

[0005] Fetal nutrition—The maternal diet is the source of the nutrition supplied to the fetus. There are operational mechanisms in pregnancy to minimize glucose utilization by the mother, there by making it available to the fetus. One metabolic action of HPL, a hormone, normally present in the mother, but not in the fetus, is believed to be blocking of the peripheral uptake and utilization of glucose by maternal tissues while promoting the mobilization and utilization of free fatty acids. The fetus is not exposed to the constant supply of glucose, even in normal pregnant women, the plasma levels vary up to 75%. Fats and proteins also are transported across the placenta, but they don't play a major role in fetal nutrition and growth.

[0006] Having realized what is the major fetal nutrient, it is important to know how it gets to the fetus and what are the factors that have effect on this important intrauterine mechanism. Placenta being the connecting link between the mother and the fetus, it is relevant to examine the adverse events that occur in this vital organ in situations like fetal growth restriction due to placental insufficiency, presuming that the maternal nutrition is not sub-optimal. Chronic vascular disease when it is further complicated by preeclampsia, commonly causes growth restriction. So it is relevant to know what happens to the placental circulation in disease situations, so that we can search for means to improve the causative states, though not cure them.

[0007] The Placental Insufficiency in Chronic Vascular and Preeclampsia/Eclampsia Disease States:

[0008] Naeye and Friedman (1979) concluded that 70% of the excess fetal deaths in preclampsia were due to large placental infarcts, markedly small placental size and Abruptio placentae. The microscopical placental lesions were resulted from reduced uteroplacental perfusion.

[0009] Vasospasm—Vasospasm is basic to the pathophysiology of precelampsia/eclampsia. It causes resistance to blood flow and accounts for the development of arterial hypertension. It is likely that vasospasm itself also exerts a damaging effect on the vessels. More over Angiotensin II appears to have a direct action on the Endothelial cells, causing them to contract. These changes likely lead to interendothelial cell leaks, through which blood constituents including Platelets and Fibrinogen are deposited subenthelially (Brunner and Gavras). The vascular changes together with local hypoxia of the surrounding tissues presumably lead to hemorrhage, necrosis and other end organ disturbances that have been observed at times with severe preeclampsia. With this scheme, fibrin deposition is then likely to be prominent as seen in fatal cases (McKay)

[0010] The principal histopathological feature of placental infarct show fibrinoid degeneration of the trophoblast, calcification, and ischemic infarction from occlusion of the spiral arteries that normally fill the intervillous spaces.

[0011] Abnormal placentation—Compared to normal women, women destined to develop preeclampsia may have a poorer physiological response to the development of the placenta. There appears to be a halt in the trophoblastic invasion of the spiral Arteries resulting in the diminished blood supply to the placenta and the fetus (Robertson et al 1975)

[0012] There may be an antigenic relationship between the placenta and the kidney (Boss 1965 Curzen 1968) and the pathological lesions found in the placenta in the cases of pregnancy induced hypertension bear some similarity to those found in the kidneys rejected after tranplantation (Robertson et al 1975). The Florescent microscopy studies of renal biopsies mentioned by Petrucco et al 1974, are in keeping with an immune mechanism affecting the kidneys. Therefore, there is some evidence to support a disturbed immunology in women with this condition—a deficient immune response of the mother to the fetus (Beer 1975).

[0013] The intervillous space: Maternal blood—The intervillous space is the maternal biological compartment of transfer where the maternal blood directly bathes the trophoblast. Substances that pass from the maternal blood to the fetal blood must traverse —1) Trophoblast, 2) Stroma of the intervillous space, 3) Fetal capillary wall. This histological barrier does not behave uniformly like a simple physical barrier; the syncytiotrophoblast either actively or passively permits, facilitates and adjusts the amount and rate of transfer of a wide range of substances to the fetus. According to Broseus and Dixon (1963), there are about 120 Spiral arterial entries into the intervillous space of the human Placenta at term, discharging blood in spurts that displaces the adjacent villi.

[0014] At least 10 variables are found to be the important factors in determining the effectiveness of the human placenta as the organ of transfer—

[0015] 1. The concentration of the substance under consideration, in the maternal plasma and in some instances the extent to which it is bound to another compound such as a carrier protein.

[0016] 2. The rate of maternal blood flow through the intervillous space.

[0017] 3. The area available for exchange across the villous trophoblast epithelium.

[0018] 4. If the substance is transferred by diffusion, the physical properties of the tissue barrier interposed between the blood in the intervillous space and the fetal capillaries.

[0019] 5. For any substance that is actively transported, the capacity of the biochemical machinery of the placenta for effecting the active transfer (eg. Specific receptors on the plasma membrane of the trophoblast).

[0020] 6. The amount of the substance metabolized by the placenta during the transfer.

[0021] 7. The area of the exchange across the fetal capillaries in the placenta.

[0022] 8. The concentration of the substance in the fetal blood, exclusive of any that is bind.

[0023] 9. Specific binding or carrier proteins in the maternal or the fetal circulation.

[0024] 10. The rate of the fetal blood flow through the villous capillaries.

[0025] Knowing these variables of fetoplacental transfer, it is important to focus our attention on those we can alter, control or positively change to the advantage of improved transfer of the essential nutrients. The factor 2—improvement of the maternal blood flow through the intervillous space can be achieved to some extent by maximum bed rest in left lateral position as soon as the diagnosis of IUGR is made. However the factors 1 and 9 are even more important for the present discussion i.e. trying to improve the concentration of the substance under consideration in the maternal plasma and the extent to which it is bound to another compounds such as a carrier protein.

[0026] The factors 2 and 3—i.e. the rate of the maternal blood flow through the intervillous spaces and/or the area available for exchange across the villous trophoblast epithelium—are the ones that are adversely affected in pathological states affecting the spiral arteries like in preeclampsia and eclampsia, thus causing decreased placental perfusion and fetoplacental transfer.

[0027] However knowing we don't have any significant control on factor 2 and 3, we should accomplish the goal of improved transfer of essential nutrients through the controllable property mentioned in factor 1 i.e. increasing the conc. of the substance under consideration, in this case, D-Glucose, the major fetal nutrient which is made available to the fetoplacental unit through selective transfer and facilitated diffusion.

[0028] Brief Description of the Current Invention—Induced Maternal Hyperglycemia-

[0029] The most common cause of intra uterine fetal growth restriction (IUGR), is vascular in nature resulting in the placental insufficiency, thus decreasing the transfer of D-Glucose, the most important fetal nutrient, across the placenta. There are other adverse metabolic events that can also happen in placental insufficiency, but the fetus has other adaptive devices to counter act those derangements, where as there is no mechanism to overcome the chronic fetal hypoglycemia that results in fetal growth retardation. The current invention is an easy, biochemically and scientifically sound way of improving fetal hypoglycemia and as a result also other associated metabolic problems of placental insufficiency in a surprisingly simple way, about which a very elaborate supportive biochemical discussion is presented in the following pages to justify the current proposed treatment.

[0030] An accelerated facilitated diffusion can be achieved by creating a transient hyperglycemia (induced diabetic state) in the mother by intravenous 10-20 hypertonic glucose infusion, up to 50-100 cc. twice or thrice a day, with or with out insulin given subcutaneously, as soon as it is confirmed that IUGR is of vascular in origin. It is interesting to note that chromosomal anomalies are also associated with reduced number of small muscular arteries in the tertiary stem villi. Chronic partial placental separation, extensive infarction, circumvillate placenta, Velamentous insertion of the cord—all these conditions also cause IUGR of vascular origin. One or both the twins affected by IUGR could be due to decreased trophoblastic area available to each.

[0031] The IV infusion as above, creates a situation like a ‘fetal meal’ during which time deprived fetal circulation can receive more glucose presented in a higher concentration in the same given amount of blood flow across the intervilous spaces. The carrier protein operating in a sub optimal way before becomes maximal in its function during this transient maternal hyperglycemic phase. After the fetal energy and growth requirements are met, Glucose can be stored in the fetal liver and also in the placenta to be used by the fetus during the times of need.

[0032] Selective Transfer and Facilitated Diffusion

[0033] Although diffusion is an important method of placental transfer, the trophoblast and chorionic villus unit exhibit enormous selectivity in transfer, maintaining different concentrations of a variety of metabolites on the two sides of the villus.

[0034] The concentration of a number of substances which are not synthesized by the fetus are several times higher in fetal blood than in maternal blood. The transfer of D-Glucose across the placenta is accomplished by a carrier mediated, steriospecific, non-concentrating process that can be saturated—Facilitated diffusion. Transfer proteins for D-Glucose, GLUT-1 and GLUT-3 have been identified in the plasma membrane (the microvilli) of human syncytiotrophoblast. GLUT-1 expression is prominent in human placenta, increases as pregnancy advances, and is induced by all growth factors. GLUT 3 is also expressed prominentl in placenta, being localized in the Syncyntio trophoblast, and the most distinctive characteristic of GLUT-3 isoform is its low Km for glucose, meaning that half maximal glucose transfer occurs at low-concentrations of glucose. More over in response to Insulin action, intracellular GLUT-3 is redistributed to the cell plasma membrane.

[0035] The membrane transport of glucose is illustrated in drawing-1, It shows that glucose (G) combines with a carrier protein (C) at point 1 to form the compound CG. This combination is soluble in the lipid so that it can diffuse (or simply move by rotation of the larger carrier molecule) to the other side of the membrane, where glucose breaks away from the carrier protein (point 2), and passes to the inside of the cell while the carrier moves back to the outside surface of the membrane to pick up still some more glucose to transport it also to the inside. Thus the effect of the carrier protein is to make glucose soluble in the membrane; without it glucose can not pass through the membrane.

[0036] The rate at which a substance passes through a membrane by facilitated diffusion depends on the difference in concentration of the substance on the two sides of the membrane (this concept being the key point of the present treatment postulation), the amount of the carrier availability and the rapidity with which the chemical (physical) reactions can take place (factors 1, 8, 9). In the case of glucose transport, the overall rate is greatly increased by insulin. Large quantities of insulin (which can be released by pancreas during a meal or hyperglycemic state) can increase the rate of glucose transport about seven to ten fold, though it is not known if it is caused by an effect of insulin to increase the quantity of the carrier protein in the membrane or increase the rate at which the chemical reaction takes place between glucose and the carrier (factor 9).

[0037] So it seems only logical to also have the mother get insulin SC or insulin mixed with the infusion of hypertonic glucose. Though there is intrinsic stimulation of insulin by maternal pancreas, supplementing insulin can be the sure way of making insulin available at the placental site to increase the rate of facilitated diffusion by many fold as described. However the insulin dose does not need to be like for a diabetic patient, because the idea is to induce maternal hyperglycemia, make adequate glucose level available at the placental site, and also to prevent pancreatic exhaustion due to hyper stimulation.

[0038] When IUGR is first suspected as due to placental insufficiency (having excluded the disease states that would not affect the maternal feto-placental vasculature), the patient has to be hospitalized, with decreased physical activity with bed rest in the left lateral position and the fetal surveillance started. At a minimum, this includes fetal movement charts, clinical and sonographic assessment of fetal growth, amniotic fluid volume, non stress test, contraction stress test, biophysical profile, daily clinical evaluation of the mother and frequent fetal heart rate monitoring. These parameters can be compared to the same readings after IV hypertonic glucose treatment is initiated, the protocol of which is not included in this writing.

[0039] The glucose supplementation to the fetus can also be done by transamniotic fetal feeding (TAFF), the studies of which were only done in animal experiments (pregnant rabbits), but practically difficult in humans due to the length of the treatment involved, and the danger of infection that can be introduced into the amniotic cavity. This difficulty can be overcome by the inventor's novel idea of using implantable ports, that are conventionally used for central venous access, the most recent version of which is the peripherally inserted central catheter (PICC), that can be implanted at the patient's bed side also, by a simple abdominal subcutaneous pocket or tunnel.

[0040] This technique can be further perfected by making it totally aseptic by using a sterile patch at the site of the port, which can be an alcohol swab, before inserting the needle for delivery into, or withdrawal from the amniotic fluid.

DRAWINGS

[0041]
FIG. 1 The membrane transport of glucose

DETAILED DESCRIPTION

[0042] The most common cause of intra uterine fetal growth restriction is vascular in nature, causing placental insufficiency and thus decreased transfer of D-Glucose, the most important fetal nutrient across the placental interface. There are other metabolic derangements also caused by placental insufficiency for which the fetus has adaptive devices to counter act the problems. How ever the placenta is the only source of glucose supply to the fetus, and it is severely affected in placental insufficiency. The current invention of treatment is about improving the amount of glucose presented at the placental interface, and improving the chronic fetal hypoglycemia, and also simultaneously improving the other metabolic derangements in a surprisingly simple way about which a very detailed biochemical discussion is made with out which the scientific basis of the current invention can not be properly understood. It is relevant here to describe more of the fetomaternal metabolism of pregnancy with out which the biochemical and clinical rationale of the current invention can not be adequately explained.

[0043] The Fetomaternal Metabolism of Pregnancy

[0044] The Maternal Metaboism-

[0045] Profound changes occur in maternal carbohydrate and fat metabolism during pregnancy as evidenced by the increased blood levels of lactate, pyruvate, and plasma lipid fractions. Fasting blood sugar is not how ever raised in pregnant woman.

[0046] It has been generally assumed that carbohydrate tolerance is impaired in pregnancy and thus pregnancy itself constitutes a diabetogenic stress for the woman. The fact that diabetes may first manifest during pregnancy (it is possible it could be present earlier, but diagnosed during pregnancy because blood glucose was checked for the first time, making the statistical figures of incidence of diabetes during pregnancy more than it actually is), that the diabetic women frequently require increased amount of insulin as pregnancy advances, the occurance of glycosuria during pregnancy—are all cited as evidence in support of this view.

[0047] How ever, the fasting blood sugar is not increased in normal pregnancy, and serial studies of carbohydrate tolerance in healthy women during gestation. Tolerance to IV glucose may in fact be improved in early pregnancy compared with that recorded in non pregnant state.

[0048] Pregnancy is characterized by major physiological adjustments affecting every system of the body. The changes are frequently on a scale other wise unknown in healthy adult life, and have led to wide spread misunderstanding and diagnostic confusion. Unless it is realized that the pregnant woman is physiologically almost another species whose health can be gauzed only against the standards of healthy women in the same physiological state, disease will be diagnosed where none exists.

[0049] While it is true that the reasons for a decreased ‘glucose tolerance’, or the more relaxed homeostatic control, possibly can not be explained to the satisfaction of the most skeptical readers, there is no reason for believing it is any thing other than physiological. It can be stated that the maternal changes are purposeful, and directed towards the welfare of the Fetus, and in cases where there is explicit hyperglycemia, a better explanation is that it is stress of pregnancy.

[0050] Though the carbohydrate tolerance is not reduced in normal pregnancy, the peripheral resistance to insulin is increased. Blood insulin levels are in fact raised in pregnancy both in fasting state and after glucose load. The paradox of increased amount of circulating insulin organism or the presence of additional anti insulin factors—like corticosteroids, catacholamines, and glucagon but the most important insulin antagonist is the Human placental lactogen (HPL), a polypeptide produced by placenta. It cross reacts immunologically with human growth hormone.

[0051] HPL, which is produced in enormous quantities in placenta, causes increase in free fatty acids (FFA), and in this respect seems more dominant than insulin, because insulin is anti lipolytic. And once there is increased free fatty acids, the maternal tissue utilize more of it, sparing glucose to be diverted to fetoplacental circulation to be utilized, which is a slow process, because the amount of glucose spared from all the tissues of the maternal body is much more and generalized, compared to what is getting into the fetus, through only the narrow umbilical cord (thus the maternal body acts as the glucose reservoir for the sustained glucose supply to the fetus). So as long as there is high levels of glucose, it is going to release insulin from maternal pancreas. However the HPL also prevents insulin's effects on the carrier transporters of glucose, apart from increasing free fatty acids that compete with glucose for their own utilization by the maternal tissues.

[0052] The maternal pancreas is only conditioned to produce insulin as glycemic response, but does not perceive that insulin and also glucose is not being effectively used by the maternal tissues except the placenta. How ever, this fundamental loop of the body's feed back mechanism which prevails during pregnancy is still not ineffective, because the rise of insulin proportional to the glucose level is needed to enable facilitated diffusion at the utero-placental interface.

[0053] Tolerance to Intravenous Hypertonic Glucose Supplement is Infact Improved During Pregnancy-

[0054] It is of common belief that pregnancy is potentially diabetogenic and tissue resistance to insulin increases, but if the biophysiology of the cause and effect of the above changes during pregnancy are analyzed, we can say that it is maternal adaptation, rather than tissue resistance, all these adaptive devices being geared to direct glucose to fetus at the expense of the mother, the maternal tissues having changed their way to using FFA more than glucose for energy and growth. These maternal adjustments are the result of a over stretched adaptation even during normal pregnancy—being so many operational devices put together to divert glucose to the fetus, which can not be helped any more during uteroplacental insufficiency, to increase the amount of glucose to be presented at the placental intervillous space, though the fetal circulation is chronically deprived of it's prime nutrients. IV glucose supplementation is some what similar to but easier than what the body tissues in pregnancy are trying very hard to do—sparing the mother using glucose, and diverting it to the fetus. IV glucose should only ease the over stretched adaptive pathways of pregnancy. So there can be sufficient theoretical basis to believe that IV glucose supplement is better tolerated in pregnancy than in nonpregnant condition. After few days of hospitalization, and teaching the protocol to the patient, it can be done at home also with the help of the home health nurse. During the hospitalization it can also be decided if the insulin supplementation is necessary or not. Choosing to give the infusion to the mother in between the meals to make it more tolerable, and physiologically more suitable, is scientifically very appealing thought. Mid night is also a preferable time though some what inconvenient to the mother.

[0055] The transitional hyperglycemia in the maternal blood can also help the fetus to build the glycogen stores in the liver, and fat in the subcutaneous adipose tissue, after meeting it's energy requirements. This storage helps the fetus to cope with the possible hypoglycemic episodes. Insulin increases the glycogen deposition in the placenta also which Claude Bernard compared to early fetal liver, or more appropriately to it's skeletal muscle, because of it's metabolic response to Adrenaline and other hormones—is release of lactate, rather than glucose. How ever, lactate is still utilized by the fetus, especially by the fetal brain.

[0056] Fetal Blood Glucose Homeostas

[0057] The fetus and the new born are more resistant to anoxia than the adult. Altered rates of glycolysis, in anaerobic conditions is generally greater than in adult tissues. But the brain that is very sensitive to interference with it's glucose supply, has little glycogen, and has similar rates of glycolysis in aerobic and anaerobic conditions. Studies showed that metabolic protection for brain during intra uterine anoxia may be provided by the ability of the fetal and neonatal cerebral tissue to metabolize substrates other than glucose such as pyruvate, lactate, and acetate. The citric acid cycle can proceed in the absence of molecular oxygen, provided that adequate supply of oxidized coenzymes are available. In fetal tissues, the synthesis of fatty acids, a process which requires the hydrogen contained in the reduced coenzymes, may be increased in anoxia. Oxidized coenzymes would thus be reformed and enable the pyruvate produced by glycolysis to be completely metabolized with release of further energy i.e. ‘coupling of lipogenesis with glycolysis and citric acid cycle’, by which hypoxia is better tolerated.

[0058] Good amount of glucose availability leads to the following pathways—

[0059] Glucose availability leads for glucose to be converted into Acetyl—co A, the Precursor for fatty acid synthesis.

[0060] The Embden Meyerhof pathway of glycolysis, that takes place mostly in the cytosol, produces Dihydroxy acetone phosphate, an intermediary product, which can be converted into glycerol 3-PO4, by glycerol 3-PO4 dehydrogenase, with the help of NADH+H which is oxidized to NAD (Nicotinamide dinucleotide), which in turn, can be utilized in glycolysis—citric acic cycle. Good circulating levels of insulin as in normoglycemic or hyperglycemic conditions, can activate the triglyceride (TGD) formation in the adipose tissue, by activating the acylation of glycerol 3-PO4.

[0061] In surplus glucose availability, hexose monophospahte shunt (HMPS), is also activated, producing NADH+H, the hydrogen of which is used in fatty acid synthesis, and HMP shunt also produces ribose sugars necessary for DNA, RNA and steroid synthesis.

[0062] NAD is also generated from NADH+H, in the path ways leading to lipogenesis in the extramitochondrial cytosol, wherein, oxaloacetate is converted into malate, in the process converting NADH+H to NAD, this step linked to transfer of reducing equivalents to NADP (the phosphorylated derivative of NAD), involved in fatty acid synthesis. This path way is the means of transferring reducing equivalents from extra mitochondrial NADH to NADP generating NAD (can be used in glucose metabolism), and NADH+H that is used in fatty acid synthesis. This path way also is very important as the link between and in the perpetuation of carbohydrate and lipid metabolism, thus saving oxygen, that is crucial to the problem of placental insufficiency.

[0063] Activation of fatty acid synthesis by adequate glucose availability can generate oxidized coenzyme NAD continuously, by which glucose helps it's own metabolism to completion, to produce pyruvate instead of lactate that can proceed into citric acid cycle, and NAD can also be utilized as the coenzyme in citric acid cycle. The biochemical details of all these mentioned path ways will be discussed in further details in the following pages.

[0064] The resistance of the fetus and neonate to hypoxia probably depends on a number of alterations in metabolic patterns in different tissues, each of which provides a small increase in metabolic efficiency, and hence over all, ensures a greater safety margin during oxygen lack. As the human fetus grows, the proportion of Linoleic acid (an essential FFA, not synthesized in the body—comes from the maternal blood), in it's subcutaneous fat decreases and the proportion of the Palmitic acid (produced with in the body) increases, and at the time of birth, Palmitic acid is twice as much as Linoleic acid. The fatty acid composition of the subcutaneous fat of the newborn is similar to that of animals given a diet rich in carbohydrate and poor in fat. Raiha (1954), pointed out that synthesis of fat from carbohydrate may provide the human fetus with means of decreasing it's oxygen requirements. Ville (1954), has estimated that the triglycerides synthesized during last months of fetal life might save the fetus a maximum of ⅙ th of the total oxygen requirements. Mylination of the brain is most rapid in the 7 th month of the fetal life, during which time the human brain would be most susceptible to the effects of under nutrition. Unfortunately, IUGR also is more pronounced at this period of intra uterine life. Cholesterol and other complex lipids are of special importance in the formation of myelin in the developing brain. Fetal tissue can synthesize most (90%), if not all, cholesterol from glucose or acetate. Also in a normal fetus, oxidation of fatty acids (use of fats for energy—i.e. fat catabolism) contributes little towards it's total energy consumption, thus saving substantial amounts of oxygen. It is consistent with the finding that the FFA levels are low in normal fetus. The respiratory quotient (RQ) of fetal tissues in vitro has also been shown to be above unity

[0065] (Roux 1966), indicating that the synthesis of FFA from carbohydrate outweighs oxidation of fatty acids.

[0066] Adequate Supply of Glucose Makes Hypoxia More Tolerable—the Biochemical Rationale

[0067] Ability of the fetus to with stand oxygen lack is related to a particular metabolic change i.e. altered rates of glycolysis and lipogenesis, and indeed the rate of glycolysis in fetal tissues in Anaerobic conditions is generally greater than in adult tissue. Citric acid cycle can proceed in the absence of molecular oxygen provided that an adequate supply of pyruvate from glycolysis of glucose molecule, and oxidized coenzymes are available.

[0068] 1. With Limited Amounts of Oxygen and also Limited Amounts of Glucose-

[0069] Glucose metabolism (glycolysis) can proceed upto the production of pyruvate both in anaerobic and aerobic path ways, producing 2 molecules of ATP and 2 molecules of pyruvate (see the path way in FIG. 1). After this step, the further pathway changes. In anaerobic conditions lactate is the end product of pyruvate with also the formation of coenzyme NAD.

[0070] With what ever amount of oxygen available, once acetyl Co-A is generated, in the extramitochondrial compartment, fatty acid synthesis can be activated, but further maintenance is only possible by availability of glucose that can initiate hexose mono phosphate shunt (HMP shunt), that is the chief source of the hydrogen required as NADPH+H, in the reductive synthesis of fatty acids. Other sources of NADPH include the isocitrate dehydrogenase reaction, and the reaction that converts malate to pyruvate catalysed by malic enzyme (NADP malate dehydrogenase). All these three pathways are also extramitochondrial like the FFA synthesis itself, and involve abundant supply of glucose, that can generate NADPH necessary for fatty acid synthesis, and these are also linked to the generation of NAD, the oxidized coenzyme necessary for glucose metabolism, making the ‘coupling of lipogenesis and glycolysis—citric acid cycle’ surprisingly efficient, even with out participation of molecular oxygen in these path ways. How ever, with limited glucose availability in placental insufficiency, the sequence of events stop at the level of the production of pyruvate and initiation of fatty acid synthesis, both of which can not proceed any further.

[0071] 2. With Limited Supply of Glucose but Adequate Amounts of Glucose Available-

[0072] The metabolic influence of the citric acid cycle extends purely beyond a catabolic function. By it's perpetual activity, it forms the hub and the central metabolic meeting point for all most all cellular activity. Nearly all the reactions and substrates of this cyclical manoeuvre have a crucial role in the synthesis of multitude of essential metabolites e.g. those concerned with amino acids, Purines, Pyramidines, long chain fatty acids and Porphyrin synthesis. Additionally, the operation of the cycle converts potential chemical energy into metabolic energy in the form of ATP.

[0073] In the pathway shown in the FIG. 2, it is shown how a surplus of glucose availability activates both the fatty acid synthesis and TGD (triglyceride) synthesis, and also provide sufficient amount of oxaloacetate—all these sparing molecular oxygen, and would generate oxidized coenzymes NAD, and NADP that help the maintenance of oxidative pathways like citric acid cycle and glycolysis. Oxygen thus spared, can be utilized for oxidative phosphorilation, where oxygen need is mandatory, to generate the needed ATP for energy.

[0074] In FIG. 2, glucose in box (1), shows the initiation of citric acid cycle. Glucose in box (2), the additional amount of glucose available, shows the path ways that are activated and perpetuated by the production of Pyruvate (3), acetyl CoA (4), and the NADPH+H, through HMPS, with what ever oxygen that is available from placenta.

[0075] Acetyl CoA, formed by the pyruvate dehydrogenase complex, participates into fatty acid synthesis (5). The hydrogen (6) needed for the co enzyme NADP (7) to be converted into NADPH+H (8), necessary for the fatty acid synthesis, is mostly supplied by the hexose monophoshate shunt (9) (HMPS), that takes place in the extramitochondrial cytosol, also the place for fatty acid synthesis. The HMPS is active in adipose tissue in the presence of high circulating glucose. During fatty acid synthesis NADPH+H (8) is

oxidized to NADP (7). The FIG. 2 also shows NADP (7), the oxidized coenzyme, to participates in the reaction that converts isocitrate (10) to a-(alpha) ketoglutarate (11), involving the isocitrate dehydrogenase enzyme complex. This cycle shows how the most important reaction in lipogenesis i.e. the formation of acetyl CoA (4), and the NADPH+H (8) are initiated by the adequate supply of glucose. The NADP (7) that is generated in the fatty acid synthesis, can in turn be further used in the HMPS, and the oxidized form of NADP is generated here also, thus saving the molecular oxygen.

[0076] The FIG. 2, also shows how the NAD, the oxidized coenzyme necessary for the metabolism of glucose is also generated during the process of lipogenesis. Acetyl CoA (4), formed from glucose (2), further participates in the citric acid cycle (12), along with oxaloacetate (13) (also produced from pyruvate by pyruvate carboxylase, the enzyme that replenishes oxaloacetate to the citric acid cycle in the presence of biotin). Adequate amounts of oxaloacetate can participate in malate shuttle (14), through the formation of a-ketoglutarate (15). It diffuses into the cytosol, and the a-ketoglutarate (16), in the cytosol can form oxaloacetate (17), that will react with NADH+H (18), to form malate (19) and NAD (20). The high lighted part of the cycle shows the malate shuttle through the cytosol and the mitochondrion, and in this shuttle NAD is generated from NADH+H, thus also saving molecular oxygen. This reaction is linked to the reduction of NADP (7) to NADPH+H, with the conversion of malate (19) to pyruvate (3) by malic enzyme (21). The formation of a-ketoglutarate (16) is necessary because oxaloacetate (13), can not pass through the mitochondrial membrane.

[0077] Acetyl CoA, the main building block for the fatty acid synthesis, can not diffuse readily into the extramitochondrial compartment, and so the citrate (22) from the citric acid cycle diffuses into the cytosol, where it undergoes cleavage by ATP citrate lyase (the citrate cleaving enzyme), like the malic enzyme, to form acetyl CoA (23) and oxaloacetate (24). The activity of the citrate cleaving enzyme increases when there is high glucose availability, which also parallels the activity of fatty acid synthesis. Acetyl CoA (23) is now available for the initiation of fatty acid synthesis, and the oxaloacetat (24) can form malate (25) via NADH+H (26) linked malate dehydrogenase (27) forming NAD (28), followed by the generation of NADPH+H (8), via the malic enzyme (21) with the formation of pyruvate (3). This path way is means of transfering reducing equivalents from extramitochondrial NADH to NADP as shown in the FIG. 3. Alternatively, malate can be transported into the mitochondrian where it is able to reform oxaloacetate. It is to be noted that the citrate transporter in the mitochondrial membrane requires malate to be exchanged with citrate.

[0078] Glycerol-3 phosphate (29), the main ingredient that combines with the FFA (5) to form TGD (30), in the adipose tissue, is derived from the intermediate product of glycolysis—the dihydroxyacetone phosphate (31), which forms the glycerol-3 phosphate (29), by reduction with NADH+H (32), catalysed by glycerol-3 phosphate dehydrogenase, also forming NAD (33) in the process. The glycerol-3 phosphate, to combine with the FFA—to form the TGD (30) is activated by insulin in glycemic conditions. The

(33) generated in the lipogenesis can be further utilized in glycolysis—citric acid cycle and NADH+H (32), generated in the glycolysis—citric acid cycle, can in turn be used for further synthesis of glycerol-3 phosphate for lipogenesis, thus again replenishing the oxidized coenzymes needed for carbohydrate metabolism as shown in the FIG. 2.

[0079] Both the NAD and NADP thus formed in the process of lipogenesis, can keep up with the maintenance of citric acid cycle, and other oxidative metabolic pathways. Molecular oxygen thus saved, can be used to generate ATP in oxidative phosphorilation of the respiratory cycle, where in, the participation of the molecular oxygen is mandatory.

[0080] In the left part of the figure are the NADP and NAD, the oxidized coenzymes saved in the different steps of the intimately interrelated pathways of the carbohydrate and the lipid metabolism.

[0081] The Other Metabolic Derangements in Placental Insufficiency

[0082] It is a legitimate concern, that the treatment of impaired glucose transfer by inducing diabetic state in the mother, can not correct the other problems inherent to the placental insufficiency, and all these problems put together would still be detrimental to the fetal well being. It is also of critical issue that adequate glucose availability in hypoxic conditions can lead to anaerobiosis and lactic acidosis, but these concerns need in depth biochemical exploration.

[0083] The notorious metabolic problems of placental insufficiency other than hypoglycemia are—1. Hypoxia 2. Hypercapnea 3. Acidosis (including ketoacidosis), and 4. Hyperlactecemia and lactic acidosis, that needs a special and separate mention.

[0084] In placental in sufficiency, the fetus has no other way to improve the hypoglycemia, as there are not any adaptive devices developed by the fetus, except growth restriction and the placenta is the only source of glucose supply. So manifestation of hypoglycemia is earlier and more urgently evident, that also leads to the development of vicious cycle of path ways that worsen the already existent metabolic derangements of hypoxia, hypercapnia, and acidosis.

[0085] How ever, for the above mentioned problems, there are other adaptive devices efficiently developed by the fetus, or else improved by the normoglycemic status, so that these metabolic derangements are not as sensitively felt as hypoglycemia. It was already explained in detail how the normoglycemic status opens the path ways for the lipogenesis, and how this crucial step improves the whole gamut of metabolic derangements caused by placental insufficiency in a cyclically beneficial way, by saving molecular oxygen. There are few more benefits of lipogenesis that will be mentioned in relevant places in the following discussion.

[0086] Hypoxia-

[0087] Impaired oxygen diffusion across the placenta is also the consequence of placental insufficiency. In the fetus there are many adaptive devices to protect against hypoxia—

[0088] 1. The high affinity of the fetal hemoglobin for oxygen.

[0089] 2. High fetal cardiac out put (minute volume) in relation to oxygen demand.

[0090] 3. High RBC (red blood corpuscles), count of the fetus, and also high MCHC (mean corpuscular hemoglobin concentration), that can carry 20-25 ml. of oxygen/dl, where as the maternal blood can only carry 15.3 ml/dl.

[0091] 4. The fetus operates at the steepest part of the oxygen dissociation curve, and therefore a relatively large amount of oxygen is released from the hemoglobin for a given drop in po2.

[0092] 5. The fetal systemic metabolic acidosis can be prevented presumably by the cardiovascular adjustments, unless the oxygen content falls below the critical level of 2 mmol/L. There will be compensatory extramedullary erythroblastemia and macrocytosis.

[0093] 6. Both the fetal and the maternal oxygen association show changes associated with pH, that give rise to double Bohr effect, which facilitates transfer of oxygen from mother to fetus.

[0094] 7. In fetus glucose can be utilized in Embden-Meyerhof path way of glycolysis which can proceed anaerobically even in the absence of oxygen, to produce pyruvate, lactate and acetate which can be utilized by the fetal brain for growth and energy requirements.

[0095] 8. Even low grade lipogenesis spares the use of molecular oxygen in generating the oxidized coenzymes needed for the major oxidative metabolic path ways, and the triglycerides synthesized during the last months of pregnancy, can save the fetus a maximum of ⅙ th of the total oxygen requirements, and also the prevention of the use of fat for energy requirements saves substantial amounts of oxygen, the mention of which was already made.

[0096] Hypercapnea-

[0097] Impaired excretion of carbon dioxide (CO2), that is exchange of CO2 at the placental site, is a reasonable concern in placental insufficiency.

[0098] CO2, like O2 is a lipophilic molecule that crosses the placenta by simple diffusion, which is regulated by the membrane surface area thickness, diffusion coefficient of the gas in the membrane phase, and the concentration gradient of the gas across the membrane. CO2 is carried in the blood predominantly as bicarbonate, with some bound to hemoglobin, as carboxyhemoglobin. The high hemoglobin content of the fetal blood compared to the mother enables it to carry more CO2 with a given pH and pCO2. As the CO2 is produced by the fetal metabolism, and raises the fetal blood levels of pCO2, the gas will diffuse across the placenta from the fetal to the maternal compartments, provided that the fetal pCO2 exceeds maternal pCO2. Maternal pCO2 falls during pregnancy by about 10 torr as a consequence of hyperventilation. A transplacental gradient of 10 torr is maintained through the later stages of pregnancy. Maternal hemoglobin has higher affinity for CO2 than fetal hemoglobin, which gives rise to a double Haldane effect that compliments the double Bohr effect. The capacity of blood for CO2 at a given pCO2 is increased by the release of O2, so maternal blood will be able to bind increasing amounts of CO2, for the same pCO2 as it passes through the placenta, while the reverse occurs for the fetal blood. This considerably augments the exchange of CO2 at the placenta.

[0099] The diffusion coefficient of CO2 is 20 times higher than oxygen, and it's diffusion across the cell membrane is instantaneous. So it's diffusion across the placenta can be still satisfactory, even when the oxygen diffusion is moderately impaired.

[0100] It is interesting to note that CO2 is required in the initial steps of fatty acid synthesis that involves the carboxylation of acetyl CoA to melonyl CoA (made possible by good glucose availability). In the synthesis of Palmitate, 7 molecules of CO2 are used, and the same number liberated subsequently. How ever, this cyclic engagement of CO2 in the fatty acid synthesis, relieves the placenta of some of the burden of it's disposal.

[0101] Urea synthesis by the fetus increases as pregnancy advances, and significant amounts of CO2 combines with ammonium in the process of urea synthesis, and it is excreted as the fetal urine into the amniotic fluid. This is also a very important way of significant amounts of CO2 disposal by the fetus.

[0102] Acidosis-

[0103] Fatty acid synthesis not only generates oxidized coenzymes, but also uses hydrogen ions. 14 hydrogen ions are used in the synthesis of Palmitate from actyl CoA, and melonyl CoA.

[0104] So during later month of pregnancy, the amount of lipogenesis that takes place, can dispose off enormous amounts of H ion concentration from the fetal blood. During hypoglycemia, there will not be any lipogenesis. On the other hand, lipolysis and beta oxidation is initiated for energy requirements (also made more prominent by decreased insulin levels due to hypoglycemia). But in the absence of glucose and lack of oxaloacetate, fatty acid oxidation produces ketone bodies which are moderately stronger acids. Once they are formed, even if glucose is made available, the ketone bodies are oxidized in preference to glucose and fatty acids, thus saturating the oxidative machinery. So even when there is enough oxygen, in the absence of glucose, ketone bodies are formed and the fetus is still going to be acidotic. Beta oxidation of palmitate itself produces 14 hydrogen atoms apart from further production of ketoacidosis. So normoglycemia can compensate for hypoxia, but oxygen can not compensate for hypoglycemia and the related metabolic consequences.

[0105] Hyperlactecemia and Lactic Acidosis-

[0106] Insulin increases glucose uptake and glycogen deposition by the placenta and 80% of placenta glycogen is anaerobically metabolized to lactate. It can be freely diffusable across the placenta either into the maternal or fetal circulation, or into the amniotic fluid. By cotransport with hydrogen ions (there is active HMPS in the placenta), lactate is probably transported as lactic acid from the placenta into the fetal circulation. The fetal tissues, especially the fetal brain can utilize lactate, but when it accumulates in excess amounts, it can cause fetal acidosis.

[0107] Giving the mother IV glucose, during fasting and mid night, avoid the maternal production of ketones (which is not uncommon even in normal pregnancy). Prevention of maternal acidosis can help for more of lactic acid to be disposed of by maternal circulation instead of the fetal circulation, at the placental site.

[0108] Production of lactic acidosis can be prevented by initiation of lipogenesis and triglyceride formation during glucose availability, during which time the Glycerol-3 phosphate (the building block of TGD) synthesis from dihydroxyacetone phosphate of glycolysis, can be initiated, that involves conversion of NADH+H to NAD, which can be further used in glycolysis, to produce pyruvate rather than lactate. Also during glycemic conditions, under the influence of insulin, when lipogenesis is activated, lactate also like pyruvate and acetyl CoA, is converted into fat.

[0109] Amniotic fluid lactic acid level can be a tool to control the amount of glucose to be given to the mother, because the raised glycogen content in the placenta will cause enhanced placental lactate production.

[0110] The above discussion emphasizes the need for glucose more than any thing else to counter act—not only the hypoglycemia but also the consequences of the metabolic derangements as a result, that would also perpetuates the other direct adverse effects of the placental insufficiency.

[0111] Adequate amounts of glucose availability precludes the need of utilization of fats for energy requirements in fetuses with uteroplacental insufficiency, and conserves oxygen. Utilization of fat for energy requirements as in beta oxidation, not only in starvation but also in conditions of normal feeding—probably accounts for about half the total oxygen consumed by the whole body. With out adequate glucose, fetal body stores of fat are utilized, making the hypoxia worse. Economides and associates (1990), who measured plasma TGD, demonstrated hypertriglyceridemia that correlated with the degree of fetal hypoxemia.

[0112] Barker and colleagues at the united kingdom medical research unit have over 20 years researched the causes of adult mortality and morbidity, related to fetal and adult life (Fraser and Cresswell 1997), and found increased risk of hypertension, and atherosclerosis in the contest of IUGR. It could be attributable to the mode of hypertrigyceridemia produced in the IUGR fetuses that could be persistent for significant part of intrauterine life.

[0113] Experimental results in animal and human atherosclerosis studies suggests, that the fatty streak represents intimal lesions resulting from the focal accumulation of lipoprotein in the vascular intima. Recruitments of leukocytes to the nascent fatty streak and their adhesion to the vascular adhesion molecule 1 (VCAM 1), and intercellular adhesion molecule 1 (ICAM 1) of the vascular intima is further made easier due to sluggish laminar flow because of polycythemia and hyperviscosity of the blood in IUGR. In this set up at least some amount of thrombotic reaction in the focal atheromatous area is possible. As per the ‘Virchow's triad’, the thrombosis of the vessel wall depends on 3 factors—the velocity of the blood flow, the viscosity of the blood, and the nature (injury) of the vessel wall, all of which are present in the IUGR fetuses in an adverse way. So in these babies the ground work is already laid in the intra uterine life, that can easily progress and manifest into atherosclerosis and hypertension in adult life. Even the smallest lesion of intra uterine life can be magnified as the baby grows, and in adult life they can assume significant proportion, just like a mole or a scar we see on a child's face that would become proportionately bigger as an adult.

[0114] Insulin is a potent positive stimulus for lipogenesis and negative stimulus for lipolysis. It inhibits the activity of the hormone sensitive lipace, reducing the release of not only FFA from the fat stores, but also glycerol. In IUGR there is prolonged and persistent hypoglycemia causing hypoinsulinemia resulting in unopposed action of lipoprotein lipase by other hormones like TSH, GH, Glucagon and ACTH, that cause lipolysis. However, because of the lack of oxygen needed for beta oxidation of these FFA, the FFA in the blood are not used. As lipogenesis is prevented by lack of insulin, the esterification of the FFA in the blood results, causing hypertriglyceridemia. In a new born growth restricted infant with poor development of striated muscle, and absence of adipose tissue, the baby's plasma and the vestigial pancreas contained no insulin (Hill 1978).

[0115] Neonatal Hypoglycemia

[0116] The level of the circulating glucose just before and soon after birth could be as low as 50 mg %, even in apparently normal babies and it could be worse in placental insufficiency.

[0117] There is inadequate or absent glycogen stores in the liver and also impaired fetal ability to release glucose from what ever glycogen stores that are available. Also the limited supply of glucose is compromised during delivery, and further cut off after delivery, compounded by explosion of physical activity in different areas of the body, including vigorous crying of the baby that was in ‘suspended animation’ in utero. That is why, in anticipation of this problem most obstetricians recommend IV glucose during delivery and early feeding of the baby after birth.

[0118] Vitamins and Other Essential Nutrients-

[0119] It can be stated that the passage of all the essential nutrients through the placenta are impaired in placental insufficiency. Thiamine and other B-complex factors would not be an exception. Thiamine is essential for carbohydrate metabolism in it's catalytic role of conversion of pyruvate to acetyl CoA, by the pyruvate dehydrogenase complex. If the fetus is deficient in it, substantially increased supply of glucose can be over whelming to the fetus and can cause accumulation of pyruvate and also can cause lactic acidosis, and all the path ways where glucose and pyruvate are utilized, would come to a halt. So, planned oral supplementation of 100 mg. of thiamine would increase the levels of thiamine presented at the intervillous space, thus ensuring required amounts getting into fetal circulation. Only small amounts are stored in the body (25-30 mg), and it's daily need increases as the carbohydrate intake increases. This hypothesis of thiamine deficiency of the fetus may not be practically found in all the fetuses with IUGR, but as there is no way to know it easily, additional supplements at least would not harm. Niacin or nicotinic acid (or Tryptophane, an essential amino acid from which it can be synthesized), from which NAD and NADP are produced in the body, and Riboflavin, from which FAD (flavin adenine dinucleotide) is produced in the body, are also essential for the carbohydrate metabolism. So also, the folic acid and phosphate supplements are useful. For patients with IUGR it is a good idea to advice the diet mostly of carbohydrates, both simple and complex, for immediate and sustained release of hexose sugars, and proteins and fats only as per the pregnancy requirements, but rich in essential amino acids and essential fatty acids, and the vitamins and minerals—called IUGR diet. The idea is based on the advantage of mostly carbohydrate utilization by the fetus, and fat anabolism in the fetal body, and no fat catabolism through intrinsic or extrinsic supplies. Snacks of the same formula can also help improving the low blood glucose levels in between meals and midnight.

[0120] A Case Study

[0121] It is of practical interest to mention about a successful fetal out come of a severely growth restricted fetus treated with hypertonic glucose. This single case study was done by me, in 1984, on a primigravid woman in her early twenties, who was found to have severely growth restricted fetus in the middle of second trimester. She was well nourished, and from good socioeconomic back ground, and there was no obvious etiological factors, or associated medical problems that could account for the IUGR. After observing the growth of the fetus by fundal height for 3-4 more weeks, it was confirmed that the fundal height did not increase, and the patient had severely compromised fetus. As the pregnancy was quite remote from term, and as the reduced physical activity, and bed rest in the left lateral position did not help, 20% IV hypertonic glucose, 50 cc. twice daily, was started, and in two to three weeks, there was immediate catch up of fetal growth, and at term she delivered a healthy baby of normal weight. No adverse effects due to the induced transient maternal hyperglycemia, was expected or observed during the pregnancy, and the patient tolerated the treatments very well.

[0122] The observed growth restriction was severe, but just with glucose supplementation, the mother delivered a normal healthy fetus at term, and none of the associated problems that can be expected due to placental insufficiency like hypoxia, and hypercapnia were found, which could have been evident by at least by some amount of fetal distress and lowered apgar score, which also supports the fact that in this set up, with mere normoglycemia the fetus can take care of the multitude of possible metabolic problems by itself.

[0123] The Amniotic Fluid Nutritional Supplement-

[0124] Nutritional supplement into the amniotic fluid (AF) is scientifically attractive proposition, as it avoids the rather uncomfortable situation of interfering with the maternal carbohydrate metabolism. The phenomenon of intrauterine fetal swallowing can be taken advantage of in this modality of treatment. 5% of glucose can be safely instilled into the amniotic fluid, with out adversely effecting the osmotic forces. A brief description of the origin, chemistry and properties of the AF as the aquatic environment of the fetus, is relevant to the present discussion.

[0125] The composition, turn over, and volume of AF depends on exchanges of molecular water and electrolytes between fetal and maternal plasma and AF, occurring across the fetal skin and the membranes and also on bulk flows—inflows due to fetal micturition, and out flows due to fetal swallowing. There are columnar cells with secretary features in the amniotic epithelium during early pregnancy, but later the amnion becomes avascular, when the turn over of the AF is maximal. So any contribution of AF by amnion, except in early pregnancy is unimportant.

[0126] Until increasing stratification and keratinization significantly reduces the permeability of fetal skin, AF is derived mainly as a filtrate of fetal plasma, by diffusion across the skin. During early pregnancy it's composition therefore resembles closely that of fetal extra celluar fluid—marginally lower sodium, and slightly higher urea in the AF than in fetal plasma, are due to the intermittent passages of very small amounts of hypotonic urine by the fetus from the end of first trimester.

[0127] When fetal skin becomes impermeable, the AF is ‘exteriorized’ from the continuum of water and electrolytes in the fetal extracellular body fluids. As a result a close relationship is no longer maintained between the concentrations of the electrolytes and other diffusible substances (and therefore osmolality) in fatal extracellular fluid and the AF. From about 20 weeks to term, AF osmolality and sodium concentration are reduced steadily and the concentration of the urea and creatinine increases. There is how ever continued simple diffusion in both directions across the fetal membranes, presumably mainly the amnion covering the placenta, so that the AF is far from being a relatively static pool, apart from the intermittent bulk flows of fetal micturition and swallowing. Towards term, AF water is probably replaced about every three hours, by the constant exchange with the mother as much as 500 ml. of water per hour. This water exchange occurs via the fetus, fetal surface of placenta, and through the surface of the umbilical cord.

[0128] 5% glucose which is isotonic with the extra cellular fluid of the maternal serum should be isotonic with the amniotic fluid, because the normal osmolality of the maternal and the fetal plasma is in the range of 260-275 mosm/kg. and so also is the osmolality of AF from 20-30 weeks of pregnancy. Instillation of 100 cc of 5% glucose twice daily, is a supplementation of 10 G. of glucose that would amount to 41 calories to the fetus, and if necessary, it can be administered thrice daily also. Even if AF is replaced every 3 hrs., still substantial amounts get into the fetal body.

[0129] Studies of transamniotic fetal feeding (TAFF) of pregnant rabbit models were conducted by Mulvihill et al in 1985, using 10% dextrose solution which has been associated with increase in fetal weight. How ever the studies of Flake et al with solutions of dextrose, amino acids, and lipids alone, or in combination did not reverse the growth restriction, seen in the natural runt rabbit fetus. The reasons for these controversial results can be only postulated. Too much of dextrose, with not enough of required vitamins needed for carbohydrate metabolism (presuming the rabbit's biochemistry as similar to human), could be over whelming to the fetal well being as already discussed. Too much of lipid supplements, with and with out dextrose, can be a stress to the oxidative machinery of the fetus, as beta oxidation is an oxygen consuming pathway, which would make the existing hypoxia worse, and the co administration of dextrose not very beneficial.

[0130] The Technique of Transamniotic Fetal Feeding (TAFF)-

[0131] The TAFF in human subjects is not as easy as it is in animal experiments, because the duration of TAFF is much longer, and the introduction of infection into the amniotic fluid can be a real danger, which can be directly proportional to the duration of the TAFF, and the number of the punctures involved. It will not be easy for the mother either. So to make it possible, with out the fear of infection, and also to make it practically feasible to the mother, the recent innovation of implantable ports (originally discovered for central venous access) can be used, that needs only one time insertion, and can be functional until the spontaneous or elective delivery of the fetus is done, and the newer version, the peripherally inserted central catheter (PICC), can be inserted at the patient's bed side also.

[0132] Implantable ports are central venous access devices that consists of a subcutaneously implantable reservoir, containing self sealing septum that can with stand over 2000 needle punctures. In the case of PICC, the reservoir is made up of a small titanium port, that is placed in a subcutaneous pocket or tunnel over the abdomen in an easily palpable and easily cleanable location, and is accessed using a Huber needle for withdrawal or delivery. The port has the advantage of requiring little daily care, and therefore interferes less with the patient's daily activities. The catheter used in this device is a polyurethane catheter placed via an abdominal skin cut down, and threaded into the amniotic cavity, and can be safely done with ultra sound guidance, to avoid the placenta. However the whole length of the catheter as used for the central venous access is not needed for uterine access, and only the required length can be cut, depending upon the patient size, to be used for threading. After the access is confirmed, and having at least 5 cms. size of the catheter in the amniotic sac, the catheter is then connected to the titanium port that is placed in the subcutaneous pocket. This design also is an easy maintenance both by the patient, and the health care worker, with only a single 5 ml. saline flush, being recommended once a week, when the catheter is not in use, and even less frequent flushing if heparinized saline solutions are used. The implantable ports have a reported catheter related sepsis rate of 3%, thrombosis of 1%, and a prospective rates of 0.06 pocket infections, and 0 bacteremic episodes per 100 catheter days.

[0133] The Sterile Patch Technique-

[0134] To make the use of the implantable ports 100% infection free, other novel techniques can be used to make the needle entry site absolutely sterile. For this, during every day use, instead of using the needle on the naked skin of the port site, after cleaning the area thoroughly, a 2″ square sterile alcohol patch, holding only it's edges while taking out of it's pouch, can be used on the port site. The needle can be inserted through the alcohol swab, thus totally avoiding contact with the naked skin. After the required amount of the nutrients are given, the needle can be taken out, with the alcohol patch still in place. This makes both the entry and the exit of the needle done totally under aseptic precautions with no skin contact at all, even if the skin is not thoroughly cleaned, especially if done at the patient's home. How ever, the patient and the home health nurse have to be thoroughly taught about the danger of infection if not done as instructed, and wearing sterile gloves, still has to be practiced during the use of the port with the alcohol patch.

[0135] The Nutritional Supplements-

[0136] The amount of dextrose that should be given to the patient should be individualized. It could be detrimental to the fetus, if too much of glucose is given in situations of severe placental insufficiency, when hypoxia can be severe, that could lead to anaerobiasis and lactic acidosis, that the fetus can not handle. Or 5 L of oxygen by nasal canula, can be administered to the mother during and for 2-4 hours after the glucose supplementation, but not continuously. Research studies on O2 administration were done that yielded controversial results. The oxygen, during the increased supply of glucose, would help aerobic glycolysis of the administered carbohydrate. It is a good idea to start with small amounts of glucose supplements and progressively increase. Until the glucose required by any mother with IUGR fetus can be determined, monitoring the AF lactic acid levels is a good idea, as it could be a reflection of too much glucose that the fetus can not handle. The danger of excessive glucose supplements to a hypoxic fetus is more in TAFF, because at least in IV glucose supplementation the amount that gets to the fetus is controlled by the placenta, that would be directly proportional to the severity of hypoxia secondary to the placental insufficiency.

[0137] The Rationale for Nutritive Treatment Instead of Early Delivery

[0138] 1. IV or TAFF glucose (dextrose) treatment to the mother is easier, physically and emotionally less traumatic, and less invasive, compared to the treatment modalities involved in caring for the premature IUGR baby in the NICU.

[0139] 2. The incidence of cesarean section can be more for the elective preterm delivery, with it's associated complications to the mother, especially when there are associated medical problems also.

[0140] 3. Uncertainaties of the fetal out come and the anxiety that is unavoidable for both the parents and the obstetrician can be over come by delivering a grown and also a mature baby.

[0141] 4. Cognition—though the literature mentions that severe disabilities are low with deliveries as early as 24-26 weeks, even mild disabilities like ADHA (attention deficit and hyperactivity) is a significant problem, especially if it can be avoidable. There is no way to know what the child's IQ ‘would have been’ if the intra uterine stay was prolonged and the IUGR treated. For the cognitive evaluation of the baby during subsequent years after birth, the right comparable parameter of the child's genetic IQ is never known, to be compared to the phenotypical IQ, to know what the child is actually missing. So the most important parameters of comparison is lacking, and one can only say that the child is not mentally retarded, but can not say how much IQ drop could have resulted. The comparison with the general population is not statistically accurate, because the comparison here involves the individual child's genetic (inherent) and phenotypical (acquired) IQ. Even siblings of the same parents can be so different, to make a statistically significant comparison.

[0142] 5. The treatment to the mother is cost effective.

[0143] 6. Termination of the pregnancy early and the subsequent management of the baby can be done only in well equipped centers with NICU and the hospitalization can be long, but the treatment of the mother can be done in small settings. In motivated intelligent patients the treatment can be done at home also with the help of the home health nurse.

[0144] 7. Complications attributable to preterm deliveries were found to be indistinguishable from the term infants only between 32-34 weeks. The incidence of the respiratory distress syndrome was found to be as high as 6% even at 35-38 weeks delivery.

[0145] 8. Neonatal hypoglycemia, polycythemia, and hyperviscosity of the blood (secondary to chronic hypoxia) can be avoided with glucose nutritional supplements and prolonging intrauterine stay. Early diagnosis of IUGR and treating with glucose will also prevent fetal triglyceridemia, and as mentioned in the recent studies, the development of hypertension and atherosclerosis in adult life.

[0146] 9. It should be the aim of the obstetrician to not only deliver a normal child, but also a child with the full potential it is genetically endowed with.

[0147] The elaborate biochemical discussion was necessary because it has many clinical Implications that need to be understood by the practicing clinician, without which confident and intelligent management of the IUGR fetus and it's mother can not be optimal.

Intrauterine growth restriction - and a postulated treatment modality for clinical research and it's biochemical rationale

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