Which hormone is responsible for maintaining pregnancy by inhibiting uterine contractions?

The hormone responsible for maintaining pregnancy by inhibiting uterine contractions is progesterone. This hormone plays a crucial role in preparing the endometrium for potential implantation of a fertilized egg and is essential for the maintenance of a viable pregnancy. By promoting a state of uterine quiescence, progesterone helps to prevent premature labor and ensure that the developing fetus has a stable environment.

During pregnancy, progesterone levels rise significantly, helping to relax the smooth muscle of the uterus. This action is vital because any contractions could lead to the expulsion of the embryo or fetus. Additionally, progesterone supports the formation of the placenta and the overall health of the pregnancy.

Though estrogen, human chorionic gonadotropin, and relaxin all have important roles during pregnancy, they do not primarily function to inhibit uterine contractions to the extent that progesterone does. Estrogen is involved in uterine growth and preparation for labor, hCG helps maintain the corpus luteum early in pregnancy, and relaxin aids in the softening of the cervix and pelvic ligaments but does not play the same central role in maintaining pregnancy as progesterone.