Which substance is a placental precursor for estradiol formation?

• A. Fetal adrenal DHEAS
• B. Maternal testosterone
• C. Maternal progesterone
• D. Fetal adrenal cholesterol

Answer: (A)

Estradiol in pregnancy is made in the placenta by aromatizing androgens provided by the fetus. The fetal adrenal gland releases DHEA and its sulfate, DHEAS, which cross into the placental tissue and are converted by placental aromatase into estrogens, including estradiol. This makes fetal adrenal DHEAS the key placental precursor for estradiol formation. Maternal testosterone can be aromatized as well, but the principal substrate driving placental estradiol synthesis is the fetal adrenal DHEAS.