A study of maternal, retroplacental and umbilical cord estradiol levels in term infants delivered by caesarean section.

Unconjugated estradiol (E2) levels were measured in 41 sets of blood from the umbilical cord vein and artery, retroplacental space and peripheral maternal blood at the time of caesarean section. Cord vein E2 levels were higher than the cord artery in the vast majority of cases, showing evidence of fetal abstraction. There was a good correlation between the cord vein and retroplacental levels but no other strong correlation was found between the parameters studied. No effect of parity or fetal sex was found.