Where does the placenta synthesize progesterone from?

The placenta synthesizes progesterone primarily from pregnenolone, which is derived from cholesterol. Maternal cholesterol is converted to pregnenolone in the placenta, and then it undergoes several enzymatic transformations to produce progesterone. This hormone is crucial for maintaining pregnancy by supporting the uterine lining and preventing contractions. Additionally, some progesterone is also produced from maternal and fetal adrenal precursors.