OCR GCSE Biology 2025 – 400 Free Practice Questions to Pass the Exam

Progesterone plays a crucial role in supporting pregnancy primarily by thickening the lining of the uterus, known as the endometrium. After ovulation, the corpus luteum (which forms from the follicle that released the egg) secretes progesterone. This hormone causes the endometrial lining to become more vascular and glandular, preparing it to house a fertilized embryo.

If implantation occurs, the thickened, nutrient-rich lining is essential for supporting the developing embryo, providing it with the necessary environment for growth and development. This process is vital to establishing and maintaining a successful pregnancy.

While estrogen does also play a role in pregnancy and is important for many bodily functions, having a direct boosting effect on levels does not specifically explain how progesterone supports pregnancy. Additionally, progesterone does not stimulate the ovaries in the context of maintaining pregnancy, and it certainly does not cause menstruation, which is a result of progesterone levels dropping if pregnancy does not occur.