Why Menstruation Remains a Medical Mystery

Humans are among the few species in which the process occurs, and although researchers have ideas about why menstruation happens, there are many unknowns. But a better understanding of the hows and whys of menstruation is needed, researchers say. "There's so much we don't understand about why this repeated event of shedding and repair happens," said Dr. Hilary Critchley, an ob-gyn and reproductive health researcher at the University of Edinburgh in Scotland.