In vitro aromatization of androgens into estrogens in placental insufficiency.

We perfused in vitro the placentas of the mothers of 3 small for gestational age (SGA) and 3 adequate for gestational age (AGA) infants. After a systemic injection of 10 mg of dehydroepiandrosterone sulfate (DHEA-S), we measured the time course of the levels of DHEA-S, unconjugated DHEA, delta 4-androstenedione (delta 4-A), testosterone (T), estrone (E1) and estradiol (E2) in perfusate. We observed a significant accumulation of delta 4-A + T and a concomitant low increase of E1 + E2 in the placental fluid of SGA infants. We conclude that the aromatase activity could be decreased in some cases of placental insufficiency. This could, at least in part, explain the accumulation of circulating androgens in the mothers of some SGA infants following DHEA-S loading test observed in vivo.