TED-Ed: Why do women have periods?

The video explores the unique biological process of menstruation, which is shared by only a few mammals, including humans. It delves into the evolutionary aspects of pregnancy, highlighting the conflict between a mother's and fetus's genetic interests. The placenta plays a crucial role in fetal nourishment, but also poses risks to the mother's health. Menstruation serves as a protective mechanism, ensuring only healthy embryos implant successfully, thus safeguarding the mother's well-being and promoting the continuation of the species.

Describe the process of implantation and its challenges.

What happens to the endometrial lining when ovulation does not result in a healthy pregnancy?