What major estrogen is produced during pregnancy?

Estriol is the major estrogen produced during pregnancy. It is primarily synthesized by the placenta and reflects the functional status of both the placenta and fetal adrenal glands. Estriol levels rise significantly as pregnancy progresses, particularly in the second and third trimesters, and are used clinically to assess fetal well-being.

While estrone and estradiol are also important estrogens, estriol is specifically the dominant form during pregnancy due to its unique synthesis pathway involving the placental production of precursors from the fetal adrenal glands. Progesterone, although crucial for maintaining pregnancy, is not classified as an estrogen. Instead, it plays a pivotal role in preparing the endometrium for implantation and preventing uterine contractions.

In summary, the focus on estriol as the primary estrogen during pregnancy emphasizes its physiological role and importance in monitoring maternal and fetal health.