What hormone is released when women become pregnant?

When a woman becomes pregnant, the hormone that plays a significant role in early pregnancy is progesterone. This hormone is produced by the corpus luteum and later by the placenta, and it is essential for maintaining the uterine lining, providing a suitable environment for the developing embryo and preventing uterine contractions that could lead to miscarriage.

While relaxin, estrogen, and oxytocin are also important hormones in the context of pregnancy, their roles differ. Relaxin helps to relax the ligaments and prepare the pelvic area for delivery, estrogen is key for the overall maintenance of pregnancy and fetal development, and oxytocin is primarily involved in labor and breastfeeding. However, none of these hormones play as central a role in the early stages of pregnancy as progesterone does.

Thus, progesterone is the hormone that is crucially released at the onset of pregnancy to support and sustain the early stages of fetal development.