[An evaluation of the plasma dynamics of the 16 alpha-hydroxy steroids in fetuses and neonates (author's transl)].

This study was done to evaluate the plasma dynamics of 16 alpha-hydroxy dehydroepiandrosterone (16 alpha OH-DHA),-pregnenolone (16 alpha OH-Preg) and -progesterone (16 alpha OH-Prog) in both the unconjugated and conjugated forms in fetuses and neonates. A comparison between second and third trimester umbilical plasma levels revealed that conjugated 16 alpha OH-DHA was already elevated in the second trimester, and both 16 alpha OH-Preg and 16 alpha OH-Prog were increased. At normal deliveries, all of the steroid levels in umbilical plasma, especially conjugates, were consistently higher than in maternal plasma. There were definite correlation between umbilical arterial and venous unconjugated and conjugated 16 alpha OH-Prog and conjugated 16 alpha OH-DHA, while no correlation of 16 alpha OH-Preg. Further, umbilical arterial 16 alpha OH-Preg showed a distinct correlation when compared to umbilical venous 16 alpha OH-Prog, suggesting that 16 alpha OH-DHA and 16 alpha OH-Preg are fetal in origin, while 16 alpha OH-Prog is synthesized in the placenta from 16 alpha OH-Preg. All of the steroid levels in the neonatal peripheral plasma up to and including the fifth post partum day were consistently higher than umbilical plasma levels. In low birth weight neonates, the umbilical plasma and peripheral neonatal plasma 16 alpha OH-Preg were consistently higher than levels found in normal birth weight neonates, while 16 alpha OH-Prog and 16 alpha OH-DHA did not show a statistical difference between low and normal birth weight neonates. The significance of these steroid dynamics and their physiological role are discussed.