Showing papers on "Fetus published in 1969"
TL;DR: The data suggest that the fetomaternal transfer of lymphocytes is common, happens at least as early as the 14th week of gestation, and may be a consequence of transplacental migration of circulating fetal lymphoid cells, as well as leakage of blood.
374 citations
TL;DR: It is shown that there is an anatomical barrier which would separate foetal antigens from maternal immunologically competent cells and also protect the embryo against destruction by sensitized lymphocytes and IgM molecules, and the mother may be incapable of damaging her foetuses immunologically.
Abstract: MANY hypotheses have been introduced to explain why the conceptus of an allogeneic mating, which differs genetically and therefore antigenically from its mother, is not rejected by the mother as an allograft1,2. Two of them deserve particular consideration. First, there may be an anatomical barrier which would separate foetal antigens from maternal immunologically competent cells and also protect the embryo against destruction by sensitized lymphocytes and IgM molecules; preimmunization against paternal antigens does not seem to harm the foetus or alter the normal course of an allogeneic pregnancy3–5. An interesting possibility is that the presence of a highly sulphated acid mucoprotein on the surface of the trophoblastic cells may serve this function2,6–8. Second, the mother may be incapable of damaging her foetuses immunologically, either because she is tolerant or because immunological enhancement is operating9. Recent claims that the placental membrane is permeable to lymphocytes10–12 and that the mucoprotein layer is not continuous over the surface of the trophoblast13 have raised some doubts about the validity of the first hypothesis, which does not seem to provide the sole explanation why antigenically foreign foetuses are not destroyed.
187 citations
TL;DR: Peripheral plasma, placental and uterine progesterone concentrations were determined in pregnant rats and were related to the effects of ovariectomy and placental dislocation on the maintenance of pregnancy.
Abstract: Peripheral plasma, placental and uterine progesterone concentrations were determined in pregnant rats and were related to the effects of ovariectomy and placental dislocation on the maintenance of pregnancy. Pregnancy maintenance correlated more closely with uterine than plasma progesterone levels, a distinction readily made following ovariectomy. During late pregnancy a uterine progesterone concentration of 2 μg/lOOg seemed sufficient to prohibit the development of parturient activity, although at midpregnancy higher uterine levels appeared necessary for the protection of fetal life. Fetal survival was critically dependent upon the gestational age at the time of ovariectomy and was linked either to a compensatory placental hypertrophy or to retention of the placentae of prematurely discharged fetuses. Under conditions in which pregnancy was maintained in ovariectomized rats, plasma, but not placental or uterine, progesterone dropped below normal preparturient levels. Adequate progesterone substitution th...
180 citations
TL;DR: Early in human gestation the fetal pancreas appears to be the major source of fetal insulin, and the fetal insulin secretion rate may be relatively unresponsive to acute changes in blood glucose concentration.
Abstract: Although insulin has been demonstrated in human fetal pancreas as early as thirteen weeks of gestation, the controls of insulin secretion in the human fetus and the magnitude of placental insulin transfer to the fetus are unknown. In pregnant women, scheduled for therapeutic abortions by abdominal hysterolomy at fifteen to twenty weeks of gestation, the fetal plasma insulin response to glucose infusion and insulin transfer across the placenta were studied as follows: (1) glucose was infused to eight fetuses in situ, and (2) insulin-I-131 was infused continuously for four to six hours to eight pregnant women via peripheral vein. Insulin was measured radioimmunologically and, following the infusion studies, was precipitated quantitatively by a double antibody method. During fasting, no difference was observed between fetal and maternal plasma glucose or in insulin levels. Although glucose administered to the fetus raised the fetal plasma glucose concentration without changing the maternal level, both fetal and maternal plasma insulin concentrations were unchanged at five and ten minutes. Human insulin-I-131 was not transferred across the placenta and no sequestration of insulin-I-131 occurred in the placenta. Early in human gestation the fetal pancreas appears to be the major source of fetal insulin, and the fetal insulin secretion rate may be relatively unresponsive to acute changes in blood glucose concentration. The placenta acts as a barrier to human insulin-I-131 but does not appear to sequester and catabolize insulin-I-131, as was previously demonstrated in human pregnancies at term.
151 citations
TL;DR: Bradykinin precursor, kininogen, is present in arterial blood of the fetal lamb by 61 days of gestation and that its concentration increases toward term and that the maximal rate of production occurs during the first few minutes after expansion of the lungs or exposure of the ewe and fetus to hyperbaric O2.
Abstract: Previous studies showed that synthetic bradykinin produced in-vitro constriction of the ductus arteriosus of the fetal lamb and guinea pig, constriction of isolated human and lamb umbilical vessels, and pulmonary vasodilatation in the fetal lamb. The present study showed that bradykinin precursor, kininogen, is present in arterial blood of the fetal lamb by 61 days of gestation and that its concentration increases toward term. We studied the bradykinin-generating system in 6 exteriorized fetal lambs. Kininogen concentrations in left atrial blood decreased within 1 to 2 minutes after beginning ventilation with O2, and free bradykinin was detected in left atrial blood. Pulmonary arterial blood kininogen concentration was not significantly altered. Kininogen concentration in left atrial blood did not fall in 4 other lambs ventilated with N2 but did fall after subsequent ventilation with O2. To study the effects of increased oxygenation in utero without lung expansion, 6 pregnant ewes were exposed to hyperbar...
119 citations
TL;DR: The present investigation was undertaken to determine whether the free amino acid concentrations changed in fetal plasma during gestation with the changes in growth rate, and to observe whether any general or individual reductions in plasma amino acid levels occurred in ‘‘small for dates” infants in whom growth is known to be retarded.
105 citations
TL;DR: Studying the mouse cytomegalovirus (MCMV) as a possible experimental model for the human infection demonstrated that MCMV infection of pregnant mice caused fetal loss without evidence of fetal loss.
Abstract: The cytomegaloviruses are highly speciesspecific agents capable of initiating prolonged active infections; although they produce little if any clinically apparent disease in the adult, they have in some species an adverse effect on gestation. The human cytomegalovirus may cause severe pathologic change in the fetus following placental transfer and may directly invade fetal tissues. Mannini and Medearis [1], while studying the mouse cytomegalovirus (MCMV) as a possible experimental model for the human infection, demonstrated that MCMV infection of pregnant mice caused fetal loss without evidence of fetal
93 citations
92 citations
TL;DR: DURING the development of the human foetus, the serum proteins differ quantitatively and qualitatively from those present during neonatal life.
Abstract: Synthesis of fetal alpha-1-globulin (AFP) during fetal life was investigated to obtain information on the level of this protein in fetal sera. Tissues and sera were obtained from fetuses born alive but who died immediately after delivery. Short-term cultures of fetal and adult tissues were carried out. The anti-AFP serum was prepared in a rabbit by immunization with serum from a 20-week-old fetus. De novo synthesis of proteins was detected and analyzed by autoradiography of the immunoelectrophoretic pattern. Synthesis of AFP was found in 28/30 fetal liver cultures. During the 10-20 weeks of gestation synthesis of AFP was greater than after this period. Culture fluids of fetal spleen thymus and lung did not contain any newly synthesized AFP. Cultures of adult liver lymph nodes and bone marrow showed no AFP production. AFP synthesis was also studied in placental tissues from 7 fetuses aged from 11-18 weeks. 2 placental cultures contained newly synthesized AFP. Levels of AFP and albumin in serum of 16 6-22 week old fetuses were determined by radial diffusion. The 6- and 7-week-old fetuses contained only traces of AFP. Protein level increased steadily to a maximum at 14-16 weeks but then decreased. In 39 cord sera the AFP level was between 3 and 17 mg/100 ml (5.5 mg average). Albumin in fetal serum increased gradually with age; after Week 20 of gestation the ratio of AFP to albumin fell below 1:10. Therefore the greatest amounts of AFP were synthesized during gestation Weeks 10-20. Synthesis then diminished--in humans as well as other mammals--possibly as a result either of the disappearance of cells exclusively producing AFP or of a regulatory mechanism at the intracellular level.
91 citations
TL;DR: The influence that estrogens and progestins have on the function of the liver in humans and in experimental animals is summarized and modification of current practices does not seem to be indicated.
90 citations
TL;DR: A premature lamb fetus was totally sustained by extracorporeal perfusion with the use of a silicone-membrane blood oxygenator and parenteral nutritional support and the fetus remained in a metabolically stable state lasting several days.
Abstract: A premature lamb fetus was totally sustained by extracorporeal perfusion with the use of a silicone-membrane blood oxygenator and parenteral nutritional support. The fetus remained in a metabolically stable state lasting several days.
TL;DR: Fetal IgG serum concentrations equaled the maternal values by the thirty-third week of gestation, and IgA and IgM were infrequently found in fetal serum, and the significance of these findings is discussed.
TL;DR: The data better support the hypothesis that diabetes produced fetal anomalies among the Pima Indians by its influence upon the intrauterine environment during early pregnancy.
Abstract: Medical records of 1,207 Pima Indian children were examined for reported congenital anomalies. Anomalies occurred in eight (38.1 per cent) of twenty-one offspring born after the onset of diabetes to mothers whose disease was diagnosed before age twenty-five, but in only 3.7 per cent of the offspring of all other women. Children born after the onset of diabetes to mothers whose disease started at or after age twenty-five, and those born to prediabetic mothers had anomalies no more frequently than the children of nondiabetic mothers. Congenital anomalies were not related to paternal diabetes. Anomalies were more frequent in children from “diabetic” pregnancies during which the mother required hypoglycemic medication than from those during which medication was not required. Although a genetic mechanism cannot be completely excluded, the data better support the hypothesis that diabetes produced fetal anomalies among the Pima Indians by its influence upon the intrauterine environment during early pregnancy.
01 Mar 1969
TL;DR: It may be concluded that on a low plane of nutrition, the foetus lives as a parasite, the tissues of thefoetus having a prior claim on the nutrients circulating in the maternal blood stream.
Abstract: One of the findings common to experiments with laboratory animals and to surveys conducted on human subjects is that the birth weight of the foetus is not substantially influenced by the protein value of the diet consumed during pregnancy (Campbell, Innes & Kosterlitz, 1953 ; McGanity, Cannon, Bridgforth, Martin, Densen, Newbill, McCellan, Christie, Peterson & Darby, 1954; Thomson, 1959). Only when severe and prolongcd malnutrition is cxperienced before conception, is obstetrical performance impaired (Beaton, 1961). I t may be concluded, therefore, that on a low plane of nutrition, the foetus lives as a parasite, the tissues of the foetus having a prior claim on the nutrients circulating in the maternal blood stream. Of the mechanisms involved in this relationship, nothing is known, although some experiments on rats fed diets sevcrely restricted in protein and calories have indicated that the endocrine system might be involved. Leathem (1966) clearly showed that reproductive failure in acute and chronic starvation is due, primarily, to a diminished synthesis and release of hormones by the pituitary gland. The importance of an intact adrenal cortex for the maintenance of pregnancy on a diet low in protein has also been demonstrated (Aschkenasy-Lelu & Aschkenasy, 1957). Information concerning the metabolic interactions of maternal and foetal physiology under conditions of optimum nutrition is even more difficult to come by. Perhaps the greatest obstacle to obtaining such information is the enormous difficulty involved in metabolic work with human subjects. What might seem an obvious approach in experimental animals is frequently impracticable in the case of a pregnant woman. The measurement of nitrogen balance is a good example. There are no difficulties with the rat. With the human subject, however, no nitrogen balance study throughout a 40-week human pregnancy has bcen attempted. The measurement of nitrogen balance for short periods during pregnancy in a few women was undertaken in the 1930s (Hunscher, Ilummell, Erickson & Macy, 1935), and it is from these investigations that some of our misconceptions regarding protein utilixation during pregnancy have arisen. We have no convenient and satisfactory method for measuring body composition in the human subject, while the carcass of the rat can be submitted to an accurate analysis for water, fat, protein and mineral content. Yet, when consideration is given to the fact that mothers existing on diets considered barely adequate for an adult woman produce healthy babies with birth weights that fall within the range we term ‘normal’, it becomes obvious that a knowledge of the changes that occur in maternal body composition during pregnancy is essential to our understanding of the relationship between mother and foetus. I n sophisticated societies, such as our own, changes in body-weight, which could be used as an indication of storage or loss of nutrients during pregnancy, are largely determined by the advice given to the mother by her obstetrician. Nevertheless,
TL;DR: Examination of the fetus revealed an absence of α-1,4-glucosidase activity in all organs and cultivated fibroblasts, confirming the in-utero diagnosis of type-II glycogenosis.
TL;DR: Preliminary evidence for a hormone formerly thought to be confined to the lower vertebrates is found and it carries the hint of molecular recapitulation and suggests that hormonal structure may depend not only on the species but also on the stage of development.
Abstract: FROM a study of the ratio of vasopressor to oxytocic activities (the V/O ratio) in foetal mammals, we have found preliminary evidence for a hormone formerly thought to be confined to the lower vertebrates. Because the hormone occurs only in the foetus, it carries the hint of molecular recapitulation and suggests that hormonal structure may depend not only on the species but also on the stage of development.
TL;DR: The data indicate that the fetal plasma concentration of growth hormone is labile, that fetal growth hormone metabolism may differ from that in the neonate, and that pancreatic islet cell responsiveness rapidly changes after delivery.
Abstract: The concentrations of plasma glucose, insulin, growth hormone, and immunoreactive growth hormone-like substance in subhuman primate fetal and maternal plasma were examined after the intravascular administration of glucose, arginine, or tolbutamide to the fetus. Cannulation of interplacental vessels permitted studies on the fetus in utero without disruption of fetal-placental-maternal anatomic integrity. Single glucose injections, glucose infusions, and arginine infusions into the fetus did not alter fetal plasma insulin concentrations. In contrast, tolbutamide injections elicited an immediate 3-4-fold increase in fetal plasma insulin concentrations. A bidirectional placental transfer of insulin was demonstrated with the use of simultaneously injected insulin-125I to the mother and insulin-131I to the fetus.
Simian fetal plasma contained a substance which cross-reacted with immunologic identity to human growth hormone. In contrast, simian maternal plasma and amniotic fluid reacted with immunologic nonidentity to human growth hormone. Although glucose administration to the fetus did not suppress nor did arginine infusion consistently augment fetal plasma growth hormone levels, the latter were observed to vary in individual experiments.
The plasma responses to the same stimuli in the neonate were also examined. In contrast to the fetal experiments, glucose injection in the neonate elicited a delayed rise in the concentration of plasma insulin. Similar to the fetus, the plasma concentration of insulin increased after tolbutamide injection and did not change in response to arginine infusion. The initial concentrations of neonatal plasma growth hormone were significantly lower when contrasted with the initial fetal plasma levels. There was no difference in the responsiveness of the fetal and neonatal growth hormone-releasing mechanisms when challenged by glucose or arginine infusion.
The data indicate that the fetal plasma concentration of growth hormone is labile, that fetal growth hormone metabolism may differ from that in the neonate, and that pancreatic islet cell responsiveness rapidly changes after delivery.
TL;DR: It is concluded that the blood glucose level of the fetus is controlled by that of the mother, but that the fetal pancreas at term may respond to hyperglycaemia by the secretion of insulin.
Abstract: The effects of a maternal intravenous glucose load on the fetal plasma levels of glucose and insulin have been studied in 11 patients before the onset of labour. Within five minutes the fetal plasma glucose concentration rose significantly, indicating a rapid transfer of glucose across the placenta. Following this, the rate of fall in fetal plasma glucose closely reflected that in the mother. Serial fetal insulin estimations carried out in 8 of the 11 subjects following maternal glucose showed an early rise in fetal insulin in four and a delayed rise in one; in the remaining three there was no definite change. It is concluded that the blood glucose level of the fetus is controlled by that of the mother, but that the fetal pancreas at term may respond to hyperglycaemia by the secretion of insulin.
TL;DR: Bilirubin metabolism and excretion in the fetus was much less efficient than in the adult, and the relationship of this functional difference to known anatomic and biochemical species differences is discussed.
Abstract: Bilirubin metabolism was studied in dog and monkey fetuses. Bilirubin-(3)H was administered to fetal animals in utero by prolonged intravenous infusion. Fetal plasma disappearance, hepatic uptake, biliary excretion, and placental transfer of bilirubin-(3)H were measured.Bilirubin metabolism and excretion in the fetus was much less efficient than in the adult. Fetal plasma levels of tritium were elevated for prolonged periods, and the combined rate of placental and fetal hepatic excretion was lower than normal values for adult hepatic excretion. Species differences were noted. Hepatic conjugation and excretion appeared to be the primary mechanism of fetal metabolism in the dog. In contrast, the amounts of conjugated bilirubin-(3)H excreted in fetal monkey bile were negligible. Small amounts of (3)H-labeled bilirubin derivatives were excreted in fetal bile, but 10 times as much of the administered material was transferred intact across the placenta and excreted by the maternal liver. The relationship of this functional difference to known anatomic and biochemical species differences is discussed. Preliminary observations on alternate routes of fetal bilirubin metabolism were obtained.
TL;DR: The results indicate that prolonged fetal survival is possible and the potential value of this "experimental model" for studying chronic fetal distress due to placental insufficiency is discussed.
Abstract: The effects of single umbilical artery ligation have been studied in 20 lamb fetuses, using chronic indwelling catheters placed in a retrograde fashion via the ligated umbilical artery in the fetal aorta. Fetal arterial blood pressure, heart rate, blood pH, PCO 2 and PO 2 were monitored at various intervals until the end of the gestation. The results indicate that prolonged fetal survival is possible. Although fetuses near term did not survive this insult, long-term survival (3 to 56 days) was observed in nine animals of earlier gestational age. After an initial period of hypoxia, acidosis, and hypercapnia, stabilization occurred and "normal" values for these parameters were observed. In spite of the apparently normal gas and hydrogen exchange between mother and fetus, profound fetal malnutrition was observed in two animals who survived 26 and 56 days, respectively. The possible mechanisms of fetal adaptation to this acute change in intra-uterine environment and the potential value of this "experimental model" for studying chronic fetal distress due to placental insufficiency are discussed.
TL;DR: A pattern of fetal weights was found in which the heaviest fetus occupied the middle position with a progressive decrease in weights toward the ovarian and cervical ends of the horn, and this theory is not applicable to the normal rat pregnancy.
Abstract: Fetal weight data from 28 litters of Wistar rats were analyzed for the effect of position in the uterine horn on fetal weight. The deviation of each fetus from the mean weight of all fetuses in a uterine horn was divided by the standard deviation of the mean. The standard scores thus obtained were studied for position effect. A pattern of fetal weights was found in which the heaviest fetus occupied the middle position with a progressive decrease in weights toward the ovarian and cervical ends of the horn. The lightest fetus in each horn was most likely to be found occupying either one of these extreme positions. These results are discussed with respect to a hemodynamic theory of fetal growth control that has been postulated for the guinea pig and mouse, and it is concluded that this theory is not applicable to the normal rat pregnancy.
TL;DR: Single intraperitoneal injections of N-isopropyl-α-(2-methylhydrazino)-p-toluamide hydrochloride (procarbazine) at doses ranging from 5–550 mg/kg were given to pregnant rats on the fifth to twelfth, fourteenth, and seventeenth days of gestation to protect the twelfth-day fetus against the teratogenic effects of procarbazine.
Abstract: Single intraperitoneal injections of N-isopropyl-α-(2-methylhydrazino)-p-toluamide hydrochloride (procarbazine) at doses ranging from 5–550 mg/kg were given to pregnant rats on the fifth to twelfth, fourteenth, and seventeenth days of gestation. Malformations were seen in twenty-first-day fetuses exposed to doses that were slightly higher than one-half (250 mg/kg on 17th day) to one forty-fifth (12 mg/kg on 12th day) the single dose that was lethal to females (550 mg/kg) when they were treated once on the fifth, sixth, ninth to twelfth, fourteenth, or seventeenth day of gestation. Tail and appendicular defects were observed after treatment on all eight days, injury to the brain only after that on the ninth day, facial clefts on the ninth or tenth day, and cleft palate and shortened jaws on the sixth, ninth, twelfth, fourteenth, and seventeenth days. Malformations were not seen with any of the doses used on the seventh or eighth day of gestation. Attempts to protect the twelfth-day fetus against the teratogenic effects of 100 mg/kg of procarbazine by administration of various amounts of L-methionine were only partially successful.
TL;DR: Results are consistent with a diminished responsiveness of the human fetal pancreas to alterations in glucose concentrations in the hour prior to birth.
Abstract: The effects of an intravenous injection of glucose (0.5 gm/kg) on the concentration of maternal and fetal serum glucose, insulin, and free fatty acids (FFA) were determined in six women in labor. The maternal hyperglycemia was accompanied by a rapid increase in maternal serum insulin concentration and a fall in maternal FFA levels. Fetal serum insulin and FFA values showed either no changes or a markedly attenuated response despite fetal hyperglycemia. These results are consistent with a diminished responsiveness of the human fetal pancreas to alterations in glucose concentrations in the hour prior to birth.
TL;DR: An attack of leptospirosis due to serotype canicola in a pregnant woman was followed in the convalescent period by death of the foetus, and previous cases of this nature are reviewed.
Abstract: An attack of leptospirosis due to serotype canicola in a pregnant woman was followed in the convalescent period by death of the foetus. Previous cases of this nature are reviewed. In certain areas where leptospirosis is known to exist among the animal population early recognition and treatment of human cases is advised, especially when they occur during pregnancy.
TL;DR: Various parameters of ovarian activity were determined for the intact or hypophysectomized pregnant mouse, as a baseline to establish the nature of luteotropic hormones in this species.
Abstract: Various parameters of ovarian activity were determined for the intact or hypophysectomized pregnant mouse, as a baseline to establish the nature of luteotropic hormones in this species.
Seventeen per cent of White Swiss mice with a vaginal plug were not pregnant at subsequent stages of gestation. The greatest number of failures occurred between days 12 and 15 of pregnancy, coinciding with the temporary absence of antral follicles and regressive changes in the vaginal epithelium. This suggests that there is a period of transient hormonal imbalance before full placental function is established, which is responsible at this time for the peak in embryonic mortality.
Two periods of luteal growth were apparent between days 1 and 4 and 10 to 14 of pregnancy. The first histologic evidence of luteal regression occurred at day 16, correlating with renewed squamous cell proliferation of the vaginal mucosa.
There were no significant differences in the number of ova shed on day 1 of pregnancy (11.0 ∓ 0.5 ova) and the subsequent number of embryonic swellings at any stage. Gestation in intact pregnant mice lasted 18 days (n = 2) or 19 days (n = 36). The number of young counted late on day 1 post partum (9.1 ± 0.5) was significantly less than the number of embryonic swellings as a result of maternal cannibalism.
Hypophysectomy on day 1 of pregnancy led to rapid histologic degeneration of the corpus luteum. In this feature, the mouse resembled the hamster rather than the rat. Day 10 of pregnancy represented the earliest time at which, at least in some animals the pituitary could be removed and pregnancy continue. Following hypophysectomy from day 11 on, luteal activity, continuation of pregnancy, fetal and placental weight and vaginal histology were comparable to intact, pregnant mice. This is similar to the hypophysectomized rat in the latter half of pregnancy but differs from the situation in the hamster.
On the basis of the present findings and results in the following paper, it appears likely that the mouse placenta, in addition to secreting a prolactin-like hormone, also produces other gonadotropins.
TL;DR: The topics which are summarized in this review are the areas of fetal metabolism, placental transfer, alterations of maternal metabolism affecting the fetus, maternal nutrition, and the factors which regulate or interfere with fetal growth.
TL;DR: Double-labelled monopalmitin containing 14C-glycerol and 3H-palmitic acid was used in vitro in intestinal segments and in vivo in intestinal loops of sheep to determine if triglycerides could be synthesized by both the monoglyceride and α- glycerophosphate pathways.
Abstract: Double-labelled monopalmitin containing 14C-glycerol and 3H-palmitic acid was used in vitro in intestinal segments and in vivo in intestinal loops of sheep to determine if triglycerides could be sy
TL;DR: These studies suggest that the correction of fetal anemia in erythroblastosis fetalis by the use of fetal blood instead of adult blood would produce a greater increase in the amount of hemoglobin capable of carrying oxygen at the low oxygen tensions characteristic of the fetal circulation.
Abstract: Extract: Intrauterine exchange transfusions were conducted in fetal sheep using adult sheep as donors. Indwelling catheters in the fetus permitted sampling of blood for 8 to 36 days following the transfusion. In the first days after the procedure there was a decreased oxygen affinity of umbilical blood, an increase of about 5 mm Hg in umbilical venous O2 tension, and a decrease of about 30% in O2 saturation. In the following weeks there was a gradual return of O2 affinity, PO2, and oxygen saturation to normal. In all of the experiments there was a good correlation between the O2 affinity of umbilical blood and the percentage of adult cells present. This correlation indicated that adult cells retained a normal O2 dissociation curve even after weeks of exposure to the new environment. Despite an increased umbilical venous PO2, the fetal reticulocyte count increased significantly after transfusion, but the oxygen capacity of umbilical blood remained within normal limits. Speculation: These studies suggest that the correction of fetal anemia in erythroblastosis fetalis by the use of fetal blood instead of adult blood would produce a greater increase in the amount of hemoglobin capable of carrying oxygen at the low oxygen tensions characteristic of the fetal circulation.