[Dynamics of steroid levels in normal pregnant and parturient woman].

An extract of a relatively small volume of plasma sample was subjected to high performance liquid chromatography (HPLC) to separate unconjugated steroids, which were subsequently assayed by specific radioimmunoassay (RIA) methods. An aliquot of the sample was hydrolysed and the conjugated steroids were also determined in a similar way. These procedures were proved to be accurate, sensitive and specific to each steroid assayed, and were applied to measure steroids in the peripheral blood of pregnant and parturient women, and in the umbilical cord blood at delivery. Steroids assayed were as follows: Estrone (E1), estradiol (E2), estriol (E3), dehydroepiandrosterone (DHA), androstenedione (A), testosterone (T), 16 alpha-hydroxydehydroepiandrosterone (16 alpha-OH-DHA), 16 alpha-hydroxyandrostenedione (16 alpha-OH-A), 16 alpha-hydroxyestrone (16 alpha-OH-E1), DHA-sulfate (DHA-S), and 16 alpha-OH-DHA-sulfate (16 alpha-OH-DHA-S). Two trends were observed in blood concentrations of unconjugated steroids during the course of pregnancy. One group of steroids, E1, E2, E3 and 16 alpha-OH-E1, continued to increase toward the onset of labor. Another group of steroid, A, T, DHA, 16 alpha-OH-DHA and 16 alpha-OH-A, on the other hand, reached a peak concentration at 36 weeks of gestation, and decreased thereafter. During active labor, unconjugated steroids tended to increase except E1. However, concentrations of T decreased during delivery as compared to those near term. Levels of DHA-S tended to fall as gestational weeks advanced, while those of 16 alpha-OH-DHA-S remained significantly high. It was indicated that a simultaneous determination of various steroids in the same blood sample obtained during pregnancy and at delivery was very useful in elucidating the role of steroids in the initiation of labor.