Which hormone is known to prevent ovulation during pregnancy?

Progesterone plays a critical role in maintaining pregnancy and preventing ovulation. During pregnancy, the levels of progesterone rise significantly, primarily produced by the corpus luteum and later by the placenta. This hormone helps to prepare and maintain the uterine lining for implantation of a fertilized egg and ensures that the environment remains conducive for fetal development.

One of progesterone's primary functions is to suppress the release of luteinizing hormone (LH) and follicle-stimulating hormone (FSH) from the pituitary gland. By inhibiting these hormones, progesterone effectively prevents ovulation, thereby ensuring that no further eggs are released during the pregnancy. This is essential because ovulation would introduce the possibility of a new pregnancy, which could jeopardize the ongoing one.

Other hormones listed, such as estrogen, testosterone, and oxytocin, have different roles in the reproductive system and do not primarily function to prevent ovulation during pregnancy. Estrogen primarily supports the growth of the uterine lining and helps with various reproductive processes, but it does not have a direct role in inhibiting ovulation like progesterone does. Therefore, progesterone is the key hormone responsible for preventing ovulation during pregnancy.