What effect does estrogen have on the female reproductive system?

Estrogen plays a crucial role in the female reproductive system, particularly in preparing the body for potential pregnancy. One of its primary functions is to stimulate the growth and thickening of the uterine lining, or endometrium. This process occurs during the follicular phase of the menstrual cycle, leading up to ovulation. A thicker endometrial lining is essential for the implantation of a fertilized egg, making estrogen a key hormone in supporting fertility.

The other options do not accurately reflect the primary roles that estrogen plays in the reproductive cycle. While estrogen does influence ovulation, it does not prevent it; rather, it facilitates the development of follicles to prepare for ovulation. Estrogen does not lower fertility; instead, it is essential for the processes that support fertility. Additionally, estrogen does not decrease menstrual cycles; it plays a role in regulating them. Therefore, the correct understanding of estrogen's effect is its role in thickening the uterine lining in preparation for possible implantation and pregnancy.