Plasma Androstenedione and Testerone During Pregnancy and in the Newborn¹

Androstenedione and testosterone were measured in the peripheral plasma of pregnant women and in the plasma from umbilical arteries and veins of newborn babies using double isotope derivative methods (Horton, 1965; Riondel et al., 1963). All values have been corrected for the blanks of the methods which were 13±7 (sd) mμg/100 ml of plasma for androstenedione and 7±3 (sd) mμg/100 ml of plasma for testosterone. Although the concentration of both steroids increased during pregnancy, testosterone increased more than androstenedione. The level of testosterone was significantly greater at all stages of pregnancy measured beginning at 13–16 weeks. Androstenedione, however, was not significantly different except at weeks 13–16 and again at 37–40 weeks. The highest levels of both steroids were observed at delivery: 420±185 (sd) mμg/100 ml plasma for androstenedione and 150±68 (sd) mμg/100 ml plasma for testosterone. In the first few days after delivery the concentration of both steroids fell to the levels found in women who are not pregnant. The concentrations of androstenedione [99±26 (sd) mμg/100 ml] and testosterone [48±28 (sd) mμg/100 ml] in umbilical vein plasma were approximately ⅓ of the levels in maternal plasma. The concentrations of testosterone were similar in babies of both sexes. In males, the levels of androstenedione in both umbilical vein [118±22 (sd) mμg/100 ml] and umbilical artery [113±16 (sd) mμ/100 ml] were significantly higher than in females [81 ± 15 (sd) mμg/100 ml in umbilical vein (p<.001) and 86±8 (sd) mμg/100 ml in umbilical artery p <.05 >.02)]. The sex difference persisted during the first few days of life.