What is the primary hormone responsible for the maintenance of pregnancy?

The primary hormone responsible for the maintenance of pregnancy is progesterone. This hormone plays a crucial role in preparing the uterine lining for implantation of the embryo and maintaining a suitable environment for the developing fetus throughout pregnancy. It helps to inhibit uterine contractions, which is vital for preventing premature labor. Additionally, progesterone supports the developing placenta and breast tissue in preparation for lactation.

While estrogen is also important during pregnancy, contributing to the development of the fetus and regulating various physiological changes, it does not fulfill the central role of sustaining pregnancy that progesterone does. Oxytocin primarily functions in initiating labor and facilitating uterine contractions during childbirth rather than maintaining pregnancy. Chorionic gonadotropin, produced shortly after conception, supports early pregnancy by signaling the corpus luteum to produce progesterone, but it is not the hormone that maintains pregnancy through its duration. Therefore, progesterone is the correct choice as it is essential for the ongoing physiological changes that support a healthy pregnancy.