Epidemiologic studies have yielded controversial information regarding an association between antenatal steroid administration and elevations in arterial blood pressure (BP). The aim of the study was to determine whether antenatal administration of a clinically relevant dose of steroids at a time when fetal nephrogenesis is at its highest results in abnormal kidney development and adult hypertension. Pregnant sheep were treated with either vehicle or betamethasone. Maternal injections were given 24 h apart at 80 d of gestational age (dGA; 0.55 of gestation). Animals were studied either as fetuses or as immature adults. Fetuses were delivered by cesarean section at 135 dGA. Adults were studied at 6 mo of age. Betamethasone administration did not induce premature labor or intrauterine growth restriction. In the betamethasone-exposed group, we found at 135 dGA a 25.5% decrease in the number of glomeruli with no differences in fetal kidney weight. In adults, mean, systolic, and diastolic arterial BPs were significantly higher, whereas there were no significant differences in heart rate over the same study period. The major finding of this study is that a single course of antenatal steroids alters renal development and is associated with elevations in arterial BP in lambs at 6 mo of age. We conclude that antenatal glucocorticoid administration under the National Institutes of Health consensus guidelines may alter human fetal renal development. (Pediatr Res 58: 510-515, 2005) Abbreviations AT, angiotensin receptor BP, blood pressure dGA, days of gestational age PAH, para aminohippuric acid RAS, renin-angiotensin systemThe pioneering work of Liggins and Howie (1) resulted in antenatal steroid treatment's becoming standard of care for enhancing fetal lung maturation in pregnancies that are threatened by premature labor between 24 and 34 wk of gestation. Following the National Institutes of Health consensus conference recommendation (2), the use of corticosteroid therapy in the United States has increased from Ͻ15% of individuals who threatened to deliver prematurely in 1990 to Ͼ75% now (3). However, the growing use of glucocorticoids in the perinatal period has become an issue of extreme concern because of the potential for untoward effects found only with long-term outcome studies (3,4). A recent epidemiologic study shows an association between antenatal glucocorticoid administration and elevations in systolic and diastolic blood pressure (BP) at 14 y of age (5). Studies in animals have also associated administration of glucocorticoids during pregnancy with hypertension in the adult offspring (6 -10). However, in these studies, either the dose of glucocorticoids or the developmental stage at which the fetus was exposed does not parallel the clinical use.Fetal exposure to excess glucocorticoids of maternal origin seems to play a central role in the development of hypertension after fetal undernutrition. Maternal adrenalectomy (11) and inhibition of adrenal function with metyrapone (12) negate the effect of protein restr...

Antenatal steroid administration is associated with alterations in fetal kidney development and hypertension. However, a causal relationship between nephron deficit and hypertension has not been established. In this study, we measured nephron number, renal function, and blood pressure in sheep exposed antenataly to betamethasone. Pregnant sheep were given 2 betamethasone doses (0.17 mg/kg) or vehicle at 80 and 81 days gestational age and allowed to deliver at term. Data were obtained from a fetal cohort and 2 adult cohorts and were analyzed by analysis of variance (ANOVA) and/or 2 sample t test. Antenatal betamethasone induced a 26% reduction in the number of nephrons in both males and females in the absence of intrauterine growth restriction and/or prematurity. Adult males presented a reduction in glomerular filtration rate (GFR; 132 ± 12.7 vs 114 ± 7.0 mL/min, P < .05). Betamethasone administration was also associated with an increase in arterial blood pressure of similar magnitude in male (mean arterial pressure [MAP] in mm Hg; 98 ± 2.7 vs 105 ± 2.4) and female (96 ± 1.9 vs 105 ± 2.4) adult sheep and the increase in blood pressure preceded the decrease in GFR in the males. Furthermore, we found no significant association between the magnitude of the decrease in nephron number and the magnitude of the increase in arterial blood pressure. Our data thus support the conclusion that exposure to glucocorticoids at a time of rapid kidney growth is associated with an elevation in blood pressure that does not appear related solely to the reduction in nephron number.

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Prolonged mild hypoxemia significantly altered fetal homeostasis as reflected by the sustained tachycardia and increased blood pressure. Fetal ECoG activity was affected significantly in a qualitatively and quantitative manner by mild prolonged hypoxemia.

We have shown that five days of mild hypoxia has significant effects on fetal ECoG activity, heart rate and blood pressure. We now studied if mild prolonged hypoxemia had an adverse effect on the fetal cardiovascular and neural responses to repeated cord occlusion and on the magnitude of neuronal damage. Fetal and maternal catheters were placed at 120 days' gestation and animals allocated at random to receive intratracheal maternal administration of nitrogen (n=8) or compressed air in controls (n=7). Five days after surgery, nitrogen infusion was adjusted to reduce fetal brachial artery pO 2 by 25%. After 5 days of chronic hypoxemia the umbilical cord was completely occluded for 5 minutes every 30 minutes for a total of four occlusions. Data are presented as mean ± SEM and were analyzed by Two Way ANOVA or two sample t test. Nitrogen infusion decreased fetal pO 2 by 26% (20.5±1.7 vs. 14.3±0.8 mmHg) without changing fetal pCO 2 or pH. Pre-existing hypoxia fetuses had a greater terminal fall in heart rate in occlusions II, III and IV, and also had a more severe terminal hypotension in the final occlusion. Pre-existing hypoxia was associated with a greater fall in spectral edge frequency during occlussions from 14.4±0.9 Hz to 6.9±0.4 Hz vs. 13.6±1.64 Hz to 10.6±0.77 Hz in controls, p<0.05. In addition, during the three-day post-occlusion period the contribution of theta and alpha band frequencies to total ECoG activity was significantly lower in the pre-existing hypoxia fetuses (p<0.05). These effects were associated with increased neuronal loss in the striatum (p<0.05). In summary, the cardiovascular and neural response indicate a detrimental effect of preexisting mild hypoxia on fetal outcome following repeated umbilical cord occlusions.