Menstruation and the menstrual cycle

Menstruation is a woman’s monthly bleeding. When a woman menstruates, the body sheds the lining of the uterus (womb). Menstrual blood flows from the uterus through the small opening in the cervix and passes out of the body through the vagina. Most menstrual periods last from three to five days.{{more}}

When periods (menstruations) come regularly, this is called the menstrual cycle. Having regular menstrual cycles is a sign that important parts of the body are working normally. The menstrual cycle provides important body chemicals, called hormones, to keep women healthy. It also prepares the body for pregnancy each month. A cycle is counted from the first day of one period to the first day of the next period. The average menstrual cycle is 28 days long. Cycles can range anywhere from 21 to 35 days in adults and from 21 to 45 days in young teens. The rise and fall of levels of hormones during the month control the menstrual cycle.

In the first half of the cycle, levels of estrogen (the “female hormone”) start to rise. Estrogen plays an important role in keeping healthy, especially helping to build strong bones and to help keep them strong. Estrogen also makes the lining of the uterus (womb) grow and thicken. This lining of the womb is a place that will nourish the embryo if a pregnancy occurs. At the same time the lining of the womb is growing, an egg, or ovum, in one of the ovaries starts to mature. At about day 14 of an average 28-day cycle, the egg leaves the ovary. This is called ovulation.

After the egg has left the ovary, it travels through the fallopian tube to the uterus. Hormone levels rise and help prepare the uterine lining for pregnancy. A woman is most likely to get pregnant during the three days before or on the day of ovulation. Keep in mind that women with cycles that are shorter or longer than average may ovulate before or after day 14.

A woman becomes pregnant if the egg is fertilized by a man’s sperm cell and attaches to the uterine wall. If the egg is not fertilized, it will break apart. Then, hormone levels drop, and the thickened lining of the uterus is shed during the menstrual period.

Women usually have periods until menopause. Menopause occurs between the ages of 45 and 55, usually around age 50. Menopause means that a woman is no longer ovulating (producing eggs) or having periods and can no longer get pregnant. Like menstruation, menopause can vary from woman to woman and these changes may occur over several years.

As noted, menstruation is a very important part of a woman’s body. You should see a doctor if: you have not started menstruating by the age of 15; you have not started menstruating within three years after breast growth began, or if breasts haven’t started to grow by age 13; your period suddenly stops for more than 90 days; your periods become very irregular after having had regular monthly cycles; your period occurs more often than every 21 days or less often than every 35 days; you are bleeding for more than seven days; you are bleeding more heavily than usual or using more than one pad or tampon every one to two hours; you bleed between periods; you have severe pain during your period; and you suddenly get a fever and feel sick after using tampons.