Growth failure in second-trimester fetuses with trisomy 21

Growth failure in the Down syndrome is common postnatally, but is thought to be less consistent in fetuses and newborns. We describe the growth of individual organs in 53 second-trimester abortuses with trisomy 21 and compare the organ weights to organ weights from 432 spontaneously aborted, but otherwise normal control specimens. Using multiple regression analysis, we found body weight to be the most significant predictor of all organ weights in normal fetuses; therefore, this variable was used to generate the regression lines to which the organ weights of trisomic specimens were compared. All trisomic fetal organs were found to be small, with an abnormal karyotype being a significant predictor of low organ weight. However, the effect on individual organs was variable, with some organs differing only minimally from the controls. Placental weights were not affected by fetal trisomy. This study demonstrates the presence of well-established, although variably severe, growth retardation in second-trimester fetuses with Down syndrome.     

Fetal growth in the baboon during the second half of pregnancy

The normal growth profile of critical fetal organs through the last third of gestation has not been documented in detail in human fetuses or the fetus of any nonhuman primate species. Recent epidemiological studies in human pregnancy suggest that fetal growth plays a major role in the programming of life-long health by modifying cardiovascular, pancreatic, brain, and liver growth. The present study aimed to produce a detailed database of individual organ growth in the fetal baboon in late gestation. Fetal organ weights were obtained from 43 baboon fetuses between 121 and 177 days of gestation. Various organs (brain, heart, kidney, femur, intestines, and spinal cord) showed no sign of slowed growth in late gestation while growth of others (lung, liver, stomach, and bladder) accelerated in late gestation. The fetal adrenal and thymus showed a decrease in growth rate over the final 20 and 10 days of gestation respectively. These observations provide a database that will permit analysis of factors responsible for regulation of normal and altered fetal organ development in this important experimental species.     

Birth Weight,Intrauterine Growth Retardation and Fetal Susceptibility to Porcine Reproductive and Respiratory Syndrome Virus

The severity of porcine reproductive and respiratory syndrome was compared in pregnant gilts originating from high and low birth weight litters. One-hundred and eleven pregnant gilts experimentally infected with porcine reproductive and respiratory syndrome virus on gestation day 85 (±1) were necropsied along with their fetuses 21 days later. Ovulation rates and litter size did not differ between groups, but fetuses from low birth weight gilts were shorter, lighter and demonstrated evidence of asymmetric growth with large brain:organ weight ratios (i.e. brain sparing). The number of intrauterine growth retarded fetuses, defined by brain:organ weight ratios greater than 1 standard deviation from the mean, was significantly greater in low, compared to high, birth weight gilts. Although γδ T cells significantly decreased over time in high compared to low birth weight gilts, viral load in serum and tissues, gilt serum cytokine levels, and litter outcome, including the percent dead fetuses per litter, did not differ by birth weight group. Thus, this study provided no substantive evidence that the severity of porcine reproductive and respiratory syndrome is affected by dam birth weight. However, intrauterine growth retarded fetuses had lower viral loads in both fetal thymus and in endometrium adjacent to the umbilical stump. Crown rump length did not significantly differ between fetuses that survived and those that died at least one week prior to termination. Taken together, this study clearly demonstrates that birth weight is a transgenerational trait in pigs, and provides evidence that larger fetuses are more susceptible to transplacental PRRSv infection.     

Developmental expression of transforming growth factors alpha and beta in mouse fetus.

Expression of mRNA for transforming growth factor alpha (TGF-alpha) and TGF-beta 1 during the fetal development of mice was evaluated by in situ hybridization. TGF-alpha mRNA was detected in 9- and 10-day fetuses but was absent in older fetuses. TGF-alpha mRNA-containing cells were found in the placenta, otic vesicle, oral cavity, pharyngeal pouch, first and second branchial arches, and developing kidneys. mRNA for TGF-beta 1 was present in hematopoietic cells of blood islands and capillaries and in the liver as it began to bud off on day 10 and function as a hematopoietic organ.     

Aberrant fetal growth and development after in vitro culture of sheep zygotes.

The effects of in vitro culture systems for sheep zygotes on subsequent fetal growth and development to day 61 and day 125 of gestation were studied. Zygotes recovered from superovulated Scottish Blackface ewes approximately 36 h after intrauterine insemination using semen from a single Suffolk sire were cultured for 5 days in (a) a granulosa cell co-culture system (co-culture); (b) synthetic oviductal fluid medium without serum (SOF-); and (c) synthetic oviductal fluid medium supplemented with human serum (SOF+). Control embryos were recovered from superovulated donor ewes at day 6 after oestrus. Embryos were transferred at day 6 to synchronous Scottish Blackface recipient ewes. In total, 146 gravid uteri were recovered, comprising 97 at day 61 (20 co-culture, 27 SOF-, 25 SOF+ and 25 control) and 49 at day 125 (13 co-culture, 8 SOF-, 6 SOF+ and 22 control) of gestation. Fetuses derived from co-cultured embryos were 14% heavier (P < 0.01) by day 61 of gestation than those derived from control embryos. Growth coefficients derived from the linear allometric equation logey = logea + b logex (where y = organ mass; x = fetal mass) were significantly greater (P < 0.05) for liver, heart, kidneys and plantaris muscle in fetuses derived from co-cultured embryos, and for liver in fetuses derived from SOF+ embryos than those for control fetuses. Fetuses derived from co-cultured embryos were 34% heavier (P < 0.001) and fetuses derived from SOF+ embryos were 18% heavier (P < 0.01) by day 125 of gestation than those derived from control embryos. Growth coefficients for liver and heart for fetuses derived from co-culture and SOF+ embryos were also significantly greater (P < 0.05) at this stage of gestation than those for control group fetuses. In contrast, allometric coefficients for these organs in fetuses derived from embryos cultured in SOF without serum supplementation were not different from those for controls. Excessive volumes of amniotic fluid (polyhydramnios) were observed in 23% of conceptuses derived from co-cultured embryos. In vitro embryo culture can significantly influence fetal growth and this study provides quantitative evidence of major shifts in the patterns of organ and tissue development.     

Study of fetal organ growth in Wistar rats from day 17 to 21

A total of 1633 Wistar rat fetuses was used to determine weights of the fetus and several fetal organs on days 17 to 21 of gestation. Heart, lung, liver, kidney, stomach, intestine, brain, femur, thyroid and adrenal weights were recorded. Growth curves of the whole body and organs were calculated. A linear semi-log relationship between organ weight and day of gestation was shown. The doubling weight times were 1.5 days for whole bodies and for organs they ranged between 0.9 (spleen) and 3.4 (adrenals) days. A correlation between the rate of organ growth and the start of the organ function was observed.     

Some effects of continuous low-dose congenital exposure to methylmercury on organ growth in the rat fetus

Congenital low-dose exposure of rat fetuses to methylmercury produced smaller offspring without anatomical abnormalities. The present study explored the mechanisms of the smallness of fetuses. The pregnant rats were given methylmercury water (25 ppm) from day 1 of pregnancy continuously until day 20 of gestation. There was a negative correlation of fetal weight and maternal and fetal mercury burden. The whole organ DNA and protein content of the livers and kidneys in the experiments were significantly lower than the control (P less than 0.05) indicating that there were fewer cells per organ in the mercury exposed fetuses. When the data were compared on a per gram of tissue basis, there was no significanct difference, indicating that the number and size of the cells of each were not diminished. The incorporation of 3H-thymidine into fetal tissue DNA was also substantially lower in the experimental group indicating decreased proliferative activity. We conclude from this study that, at least for some major organs, the decreased size in the mercury exposed fetuses is due to fewer cells in the organs due to decreased proliferative activity.     

Modulation of the progesterone receptor in the fetal uterus of the progesterone-primed guinea pig in vivo and in organ culture

Guinea pig fetuses were treated with progesterone for 7 days before placing fetal uteri in organ culture to see if progesterone pre-treatment of fetuses in utero would permanently inhibit the spontaneous rise in progesterone receptor which occurs in organ culture. The data show that: the basal level of progesterone receptor in fetal uteri was not affected by the progesterone treatment and progesterone receptor concentrations in vitro were also not inhibited. When guinea pig fetuses were treated sequentially with progesterone and estradiol, estradiol failed to provoke an uterotrophic effect but it retained its ability to stimulate progesterone receptor concentrations.     

Human fetal development between 90 and 170 days postmenses

Linear measurements, total weights, and organ weights of 133 fresh human fetuses were obtained after therapeutic abortion between 90 and 170 days postmenses. Great apparent variation was observed in fetuses of given ages, especially in organ weights. There was no evidence of sex or parity differences.     

Comparative study of clonal growth and differentiation of mesenchymal stromal cells from rat fetal liver at different developmental stages

Fetal liver during period of its hematopoietic activity contains mesenchymal stromal cells (MSC) that are known to play a major role in establishing hematopoietic microenvironment. These cells are capable of clonal growing and multilineage differentiation, but only limited data exist about changes in their properties during prenatal development. We compared cloning efficiency of MSC from liver of 14, 16 and 20 day rat fetuses and evaluated their potentials to in vitro osteo- and adipogenesis and in vivo chondrogenesis after whole organ ectopic transplantation. Content of clonogenic MSC in suspension of liver cells was maximal in 16 day fetuses and to a lesser extent in 20 day ones. MSC derived from 16 day fetuses demonstrated maximal potential to estimated lineages. Osteogenic potential of MSC from 14 day fetuses was comparable to whereas their adipogenic and chondrogenic abilities were inferior to that from 16 day fetuses. Cells from 20 day fetuses had only weak adipogenic potency and failed to differentiate into osteogenic of chondrogenic pathways. The results indicate that both number and differentiation potential of MSC in developing rat liver correlate with dynamics of hematopoiesis in this organ. Detected changes may be ascribed to the decline of hematopoiesis in liver and acquisition its definitive functions.     

Studies of the teratogenic potential of exposure of rats to 6000-MHz microwave radiation. I. Morphologic analysis at term

Thirty-six pregnant Wistar strain albino rats were exposed throughout pregnancy to 6000-MHz microwave radiation at a power density level of 35 mW/cm2 or were used as controls. The irradiation did not cause a significant increase in maternal body temperature as measured by a rectal thermocouple. The rats were randomly assigned to one of four groups: home cage control (5), anechoic chamber control (10), sham-irradiated concurrent control (10), and irradiated (11). All animals were killed on the 22nd day of gestation, and maternal tissues were removed and weighed and maternal blood samples were taken. The 384 resultant fetuses and their placentas were individually weighed, fixed, and dissected to determine normality. Teratologic evaluation included the following parameters: maternal weight and weight gain; mean litter size; maternal organ weight and organ weight/body weight ratios; body weight ratios of brain, liver, kidneys, and ovaries; maternal peripheral blood parameters including hematocrit, hemoglobin, and white cell counts; number of resorptions and resorption rate; number of abnormalities and abnormality rate; mean term fetal weight. The irradiated fetuses exhibited slight but statistically significant growth retardation at term. Term maternal monocyte count was also significantly depressed. No other parameters differed between the control groups and the irradiated group.     

Organ and gestational age effects of maternal nutrient restriction on global methylation in fetal baboons

Background  A sub-optimal intrauterine environment alters the trajectory of fetal development with profound effects on life-time health. Altered methylation, a proposed epigenetic mechanism responsible for these changes, has been studied in non-primate species but not nonhuman primates. We tested the hypotheses that global methylation in fetal baboon demonstrates organ specificity, gestational age specificity, and changes with maternal nutritional status.
Methods  We measured global DNA methylation in fetuses of control fed (CTR) and nutrient restricted mothers fed 70% of controls (MNR) for brain, kidney, liver and heart at 0.5 and 0.9 gestation (G).
Results  We observed organ and gestation specific changes that were modified by maternal diet. Methylation in CTR fetuses was highest in frontal cortex and lowest in liver. MNR decreased methylation in 0.5G kidney and increased methylation in 0.9G kidney and frontal cortex.
Conclusion  These results demonstrate a potential epigenetic mechanism whereby reduced maternal nutrition has long-term programming effects on fetal organ development.     

Intrauterine growth restriction in rats is associated with hypertension and renal dysfunction in adulthood

Epidemiological studies have produced evidence that unfavorable intrauterine environments during fetal life may lead to adverse outcomes in adulthood. We have previously shown that a low-sodium diet, given to pregnant rats over the last week of gestation, results in intrauterine growth restriction (IUGR). We hypothesize that pups born with IUGR are more susceptible to the development of hypertension in adulthood. IUGR fetuses and rats aged 1 wk were characterized for organ growth and renal morphogenesis. The adults (12 wk) were evaluated for weight, systolic blood pressure, activity of the renin-angiotensin-aldosterone system (RAAS), and renal function; hearts and kidneys underwent a histological examination. Brain and cardiac ventricle-to-body ratios were increased in IUGR fetuses compared with age-matched controls, whereas the kidney-to-body ratio was unchanged. Systolic blood pressure was elevated in both IUGR male and female adults. Plasma aldosterone levels were not correlated with increased plasma renin activity. Moreover, urinary sodium was decreased, whereas plasma urea was elevated in both males and females, and creatinine levels were augmented only in females, suggesting a glomerular filtration impairment in IUGR. In our model of IUGR induced by a low-sodium diet given to pregnant rats, high blood pressure, alteration of the RAAS, and renal dysfunction are observed in adult life. Differences observed between male and female adults suggest the importance of gender in outcomes in adulthood after IUGR.     

Growth inhibition of human embryonic and fetal rat bones in organ culture by rubella virus.

Paired organ cultures of metacarpal, metatarsal, and long bones of previable human embryos of 7 to 12 weeks' gestation and tibias of 17-day rat fetuses with inoculated with live or ultraviolet-inactivated rubella virus or control fluids and the growth of the bones was measured by increase in wet weight. In several cultures the ability of the human bones to incorporate 35S, a measure of rate of mucopolysaccharide synthesis, was tested. Growth of human and rat bones was retarded in cultures inoculated with live virus but not in cultures inoculated with inactivated virus or control fluids. Mean 35S uptake was increased by approximately 25% in virus-inoculated cultures of bones of 9- to 12-week human embryos. No histological abnormalities were seen. These findings suggest that (1) defective bone growth in congenital rubella is a direct effect of viral infection of bone, (2) a disorder of mucopolysaccharide syntheses may contribute to the osseous lesions that occur in this disease, and (3) organ cultures of human embryonic and fetal rat bones may serve as convenient models for studying the pathogenesis of this virus-induced congenital osteopathy.     

Nonvascular needle and shunt placements for fetal therapy.

The nonvascular placement of needles and shunts for the in utero treatment of fetuses with fluid-filled, space-occupying anomalies has been done for about 10 years. The rationale for this approach is to attempt to prevent progressive impairment of organ function or lethal damage by early decompression. Experience has taught us that the key to success in these cases is the exclusion of associated anomalies and the use of appropriate tests to assess the residual organ function at the time of first diagnosis. In fetuses with hydrothorax, shunts can prevent pulmonary hypoplasia, and in those with obstructive uropathy, they can prevent the development of progressive lung hypoplasia and renal damage before a fetus is fully viable. In fetuses with ovarian cysts, prenatal puncture is occasionally indicated, but in those with hydrocephalus, the beneficial effect of prenatal drainage is more controversial. The catheters used for in utero placement have been improved and carry a smaller risk than open fetal surgical procedures.     

Effect of restriction of placental growth on oxygen delivery to and consumption by the pregnant uterus and fetus

Endometrial caruncles were excised from 13 sheep (caruncle sheep) before pregnancy to restrict placental growth. In subsequent pregnancies, half the caruncle fetuses were growth retarded or small (weight more than 2 SD below mean weight for control fetuses) with the remainder, normal-sized (weight within 2 SD of mean weight for control fetuses). The caruncle and 16 control sheep, each with indwelling vascular catheters, were studied between 121 and 130 days of pregnancy. Oxygen delivery to and consumption by the pregnant uterus in caruncle sheep with small fetuses was significantly reduced compared to controls while oxygen extraction was significantly increased. Oxygen tension (P02) and content in the common umbilical vein and in the descending aorta were significantly lower in small caruncle fetuses compared to controls but only P02 was lower in normal-sized caruncle fetuses. Oxygen delivery to, and consumption by, the fetus was significantly reduced in normal-sized and in small caruncle sheep compared to controls while oxygen extraction was increased in small caruncle sheep. Utero-placental oxygen consumption was significantly lower in caruncle sheep with small fetuses compared to that in controls. Despite these changes, oxygen consumption by the gravid uterus and fetus, per kg of tissue mass, was similar in both groups of caruncle and in control sheep. Utero-placental oxygen consumption per kg of utero-placental mass in caruncle sheep with small fetuses was not significantly different to that in sheep with normal-sized caruncle or control fetuses, although it averaged only 25% of that in controls. It is concluded that intrauterine growth retardation following restriction of placental growth is associated with a reduced supply of oxygen to both the pregnant uterus and fetus and a redistribution of oxygen to the fetus. This is due to the disproportionate maintenance of fetal growth relative to that of the placenta, since oxygen consumption by either, in terms of tissue mass, was not altered. Further, the greater uterine and fetal extraction of oxygen suggests that a smaller margin of safety may exist between supply and demand in intrauterine growth retardation.     

Circulating insulin-like growth factor-I and -II concentrations are not dependent on pituitary influences in the midgestation fetal sheep

Studies were performed to investigate the possible role of pituitary factors on the regulation of circulating concentrations of insulin-like growth factor-I and -II in the midgestation sheep fetus. Four fetuses were decapitated at 59-64 days of gestation and fetal serum obtained at sacrifice at 90-102 days of gestation. Insulin-like growth factor-I and -II concentrations were similar in these samples to those from 6 control fetuses (83-102 days). A further 4 fetuses were studied following electrolytic destruction of the median eminence of the hypothalamus at 108-110 days of gestation. Four sham operated controls were also studied. Circulating growth hormone concentrations were markedly reduced (P less than 0.01) by destruction of the median eminence. However neither insulin-like growth factor-I nor -II levels differed from those of sham operated fetuses. We conclude that, in the midgestation fetal sheep, growth hormone is not essential for the maintenance of circulating concentrations of insulin-like growth factor-I or -II.     

Early fetal hypoxia leads to growth restriction and myocardial thinning

Hypoxia is necessary for fetal development; however, excess hypoxia is detrimental. Hypoxia has been extensively studied in the near-term fetus, but less is known about earlier fetal effects. The purpose of this study was to determine the window of vulnerability to severe hypoxia, what organ system(s) is most sensitive, and why hypoxic fetuses die. We induced hypoxia by reducing maternal-inspired O2 from 21% to 8%, which decreased fetal tissue oxygenation assessed by pimonidazole binding. The mouse fetus was most vulnerable in midgestation: 24 h of hypoxia killed 89% of embryonic day 13.5 (E13.5) fetuses, but only 5% of E11.5 and 51% of E17.5 fetuses. Sublethal hypoxia at E12.5 caused growth restriction, reducing fetal weight by 26% and protein by 45%. Hypoxia induced HIF-1 target genes, including vascular endothelial growth factor (Vegf), erythropoietin, glucose transporter-1 and insulin-like growth factor binding protein-1 (Igfbp-1), which has been implicated in human intrauterine growth restriction (IUGR). Hypoxia severely compromised the cardiovascular system. Signs of heart failure, including loss of yolk sac circulation, hemorrhage, and edema, were caused by 18-24 h of hypoxia. Hypoxia induced ventricular dilation and myocardial hypoplasia, decreasing ventricular tissue by 50% and proliferation by 21% in vivo and by 40% in isolated cultured hearts. Epicardial detachment was the first sign of hypoxic damage in the heart, although expression of epicardially derived mitogens, such as FGF2, FGF9, and Wnt9b was not reduced. We propose that hypoxia compromises the fetus through myocardial hypoplasia and reduced heart rate.