What hormone is released when women become pregnant?

The hormone that is primarily associated with the onset of pregnancy is progesterone. When a woman becomes pregnant, the body produces higher levels of progesterone, which plays a crucial role in preparing the uterus for the fertilized egg to implant, maintaining the uterine lining during the initial stages of pregnancy, and inhibiting uterine contractions. This helps to create a stable environment for the developing embryo.

While relaxin is also released during pregnancy, its primary function is to help relax the pelvic ligaments and soften the cervix in preparation for childbirth, which happens later in the pregnancy journey. Estrogen levels do increase during pregnancy but are not the initial hormones released that signal pregnancy. Oxytocin is involved in labor and postpartum processes but does not play a role in the early stages of pregnancy. Thus, progesterone is the key hormone directly associated with the establishment and maintenance of pregnancy.