Unconjugated estriol (E3) was quantified in serum of umbilical cord blood of 533 newborn infants, 360 of whom were delivered between 23 and 37 wk of gestation. Serum E3 levels rose (F = 7.71, p < 0.0001) as a function of gestational age; the mean concentration of E3 at 37.5-42 wk of gestation (105 ng/ml, n = 173) was significantly higher than that in serum of newborns delivered at 23-28 wk of gestation (63 ng/ml, n = 33). Umbilical cord serum levels of E3 were significantly higher among newborns delivered vaginally between 31.5 and 42 wk of gestation than among newborns delivered by cesarean section (p < 0.005). Although serum E3 levels correlated highly (p < 0.0001) to newborn weight throughout the entire period of gestation, there was no relationship of newborn weight to umbilical serum E3 levels within a given gestational period. Also, the umbilical serum levels of E3 in male infants were similar to those of female infants at each gestational age. Significant changes in umbilical serum levels of E3 as a function of gestational age were not observed among newborns (n = 90) who developed respiratory distress syndrome (RDS). The mean umbilical serum concentration of E3 in newborns delivered at 34.5-37 wk of gestation who developed RDS were significantly lower (p < 0.01) than that in similar aged newborns whose lung function was normal. Based on the results of multiple logistic regression analyses, we estimated that for each week between 28.5-36 wk of gestation, the probability of RDS in infants in whom the E3 level was at the 10th percentile was about 7% greater than that in newborns in whom the E3 level was at the 50th percentile; the probability of RDS in infants with an E3 level at the 90th percentile was about 10% lower than that in newborns in whom the E3 level was at the 50th percentile. These data are suggestive that with normal intrauterine development, fetal tissues are exposed to unconjugated E3 in progressively increasing concentrations during the latter half of gestation. When fetal levels of E3 do not increase during this critical period of development, there is an increased risk of development of RDS.
ASJC Scopus subject areas
- Pediatrics, Perinatology, and Child Health