Menstruation

Symptoms

Women typically experience a range of symptoms associated with menstruation, particularly uterine cramps (“dysmenorrhea”) that are caused by the contractions of [Page 928]the uterine muscles as the uterus expels the blood from the woman's body. Menstruation typically occurs from early teenage years until mid-to late-40s, though timing of onset of menstruation as well as menopause varies greatly. Girls can begin menstruating as early as 8 or 9 years old, and women can go through menopause as late as their sixties. In average premenopausal women, menstruation pauses only during pregnancy and for some time after childbirth (“amenorrhea”). Typically, menstruation is a physiological event that allows women's bodies to rebuild the endometrium every fertility cycle, thus ensuring adequate opportunity for fertilization should she desire to become pregnant.

Many women refer to menstruation as their “period” (short for “menstrual period”). Women sometimes say they are “on the rag” or “visiting Aunt Flo” as informal or slang references to the event. Women may also say they are “late” when their menstrual cycle does not start on time as expected, sometimes indicating pregnancy. Irregularity of menstrual cycles is fairly normal, as stress, emotional problems, physical strain, malnutrition, and hormonal imbalances can cause menstruation to become irregular. Hormonal birth control methods like the birth control pill, Depo Provera, hormone-based IUDs, Norplant, and the patch also can cause menstruation to cease entirely or become much lighter. Birth control pills control for a shorter menstrual cycle precisely every 28 days, while Depo Provera and Norplant often completely eliminate the menstrual cycle. New birth control options like Seasonale allow for a period every three months.

Menstruation is part of the reproductive cycle and typically occurs every 28 days. In a typical menstrual cycle, women will bleed during days one through five and will ovulate on day 14 and 15 of the cycle. They will then bleed again at the start of the next cycle. During ovulation, women are fertile and can become pregnant. While it is technically possible to become pregnant during menstruation-as an egg could be released irregularly during this time, or sperm could be inserted into the vagina and wait for an early ovulation cycle-it is not likely. Debates about whether women synchronize their menses while cohabitating is also debated; some researchers believe that this does occur, while more recent research suggests that this does not occur. Disagreements about the evolutionary purpose of menstruation also continue, as researchers cannot fully explain why human females do not absorb the endometrium like many other female mammals do during their menstrual cycles. Notably, only humans and their close evolutionary relatives (e.g., chimpanzees, gorillas) menstruate through the vagina with distinct discharge. Other mammals have a menstruation period but their bodies simply absorb the tissue and blood into the body, perhaps because their tissue is less complicated than human tissue.

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