Needs Contributes Lacks

Mother

Placenta

Fetus

Progesterone LDL Cholesterol Adequate synthetic capacityEstrone (for progesterone and estrogens)EstradiolEstriol

3β-hydoxysteroid dehydrogenase(3β-HSD)Aromatase (P-450arom)

Adequate cholesterol capacity17α-hydroxylase (for estrone and estradiole synthesis)17,20-desmolase(for estrone and estradiole synthesis)16α-hydoxylase(for estriol synthesis)

17α-hydroxylase (for estrone and estradiole synthesis)17,20-desmolase(for estrone and estradiole synthesis)16α-hydoxylase(for estriol synthesis)

3β-hydoxysteroid dehydrogenase(3β-HSD)Aromatase (P-450arom)