A study of variation in the length of the menstrual cycle.
D000375:Aging; D001942:Breast Feeding; D005260:Female; D006801:Humans; D007774:Lactation / Q000502:physiology*; D008597:Menstrual Cycle; D008598:Menstruation / Q000502:physiology*; D011247:Pregnancy / Q000502:physiology
AGING/effects; LACTATION/physiology; MENSTRUATION/physiology; PREGNANCY/physiology