Progesterone and estrogen are essential hormones in the female reproductive system that work together to control uterine function and facilitate reproduction. Progesterone plays a central role in producing a receptive uterus capable of supporting pregnancy in post-menopausal women receiving donor embryos. Progesterone levels decline dramatically during menopause. Progesterone deficiency can lead to abortion, and supplementation with progesterone has been shown to significantly reduce miscarriage rates in women with recurrent pregnancy loss or threatened abortion.