Events surrounding a baby girl's birth may affect the age at which she later goes through menopause.
A woman's ovaries hold the most eggs while she is in her mother's womb: about 5 million at 24 weeks gestation. By birth, she's left with roughly 2 million. The count continues to fall until menopause, when the last 1,000 eggs of her supply begin to run out and menstruation and fertility end.
Prenatal exposure to chemicals linked to breast cancer