Menstruation & Menstrual Cycle


  • In the U.S. the average age of menarche-a girl’s first period-is 12 years, although it’s normal to start as early as 10 or as late as 16. Menopause when periods stop-usually occurs around age 50, although that, too, can vary by several years. Except perhaps for the first two years of menstruation-and barring pregnancy, nursing, and certain illness or other problems-the reproductive cycle repeats with predictable regularity every month
  • Exercise, diet and stress can delay the onset of menstruation or alter cycles once they’ve been established. Gymnasts, ballerinas and others who exercise strenuously can sometimes delay the onset of their periods, so there may be a 16- or 17-year-old in that group who hasn’t started menstruating. The connection between exercise and amenorrhea (absence of menstrual periods) may be related to body fat content, because fat affects estrogen. Young women who are very thin from malnourishment may not start menstruating until they gain weight, with a certain portion of that weight being fat.
  • Young women with severe eating disorders such as anorexia or bulimia often do not menstruate. It is recommended that a girl see her doctor if she hasn’t started menstruating by age 16, or if by age 13 or 14 she hasn’t begun to develop breasts or pubic and underarm hair.


  • Many young women have very irregular periods during the first few years of menstruating-even skipping some months, until the system is well-tuned.
  • In addition, young women don’t always ovulate every month when they first get their periods. There’s no sure way for a young woman to know which month she is ovulating and which she is not. So, from time to time her periods begin, a young woman should assume she can get pregnant each and every month, even if her periods are irregular.
  • Eventually, periods become regular, but even when they do, a missed or late period once a year – especially at a stressful time – is considered normal. Strenuous exercise and eating disorders can also cause previously regular menstrual cycles to become irregular or stop completely
  • Periods last from 3 to 5 days, but anywhere from 2 to 7 days is normal. The amount of blood varies, usually starting out light, then heavy, then light again. Use pads or tampons to absorb the flow.
  • Menstruation is just one part of the menstrual cycle, in which a woman’s body prepares for pregnancy each month. A cycle is counted from the first day of one period to the first day of the next. An average cycle is 28 days, but anywhere from 23 to 35 days is normal.


  • Some women feel a period coming days before they get it. Others are hardly aware they have it. Friends who compare notes about their periods will probably find that menstruation-the monthly shedding of the lining of the uterus, or womb-affects each of them a little differently, both physically and emotionally.
    · The menstrual cycle has its up s and downs of hormones, and different people react differently to hormonal swings. Just before and during menstruation, levels of the female hormones estrogen and progesterone are low. That’s when some women feel bloated, irritable or blue, or “just crummy” might mean cramps, sore breast, backache, headache, nausea, and feeling tired.
  • A day or two after your period starts you begin to feel better. Hormone levels go back on the upswing and you get back to what you’re accustomed to during the rest of your cycle.
  • Some 20 to 40 percent of menstruating women have PMS, or premenstrual syndrome. Starting anywhere from mid-cycle to a few days before menstruation begins, women with PMS may have one or all of a virtual laundry list of physical and emotional symptoms. They include breast swelling and tenderness, fluid retention, increased thirst or appetite, craving for sweets and salty foods, headaches, anxiety, restlessness, irritability, depression, hostility, and loss of self confidence. PMS doesn’t usually affect teenagers, though. It increases with age and is more prevalent in the 30’s and 40’s.


  • Estrogen and progesterone levels are very low at the beginning of the cycle. During menstruation, levels of estrogen, made by the ovaries, start to rise and make the lining of the uterus grow and thicken. In the meantime, an egg (ovum) in one of the ovaries starts to mature. It is encased in a sac called Graafian follicle, which continues to produce estrogen as the egg grows.
  • At about day 14 of a typical 28-day cycle, the sac bursts and the egg leaves the ovary, traveling through one of the fallopian tubes to the uterus. The release of the egg from the ovary is called ovulation.
  • Some women know when they’re ovulating, because at mid-cycle they have some pain-typically a dull ache on either side of the lower abdomen lasting a few hours. The medical word for this is mittelschemerz, from the German, meaning middle pain. Some women also have very light bleeding, or spotting, during ovulation.
  • After the egg is expelled, the sac-now called a corpus luteum-remains in the ovary, where it starts producing mainly progesterone. The rising levels of estrogen and progesterone help build up the uterine lining to prepare for pregnancy.
  • The few days before, during and after ovulation are a woman’s “fertile period”-the time when she can become pregnant. Because the length of menstrual cycles varies, many women ovulate earlier or later than day 14. It’s even possible for a woman to ovulate while she still has her period if that month’s cycle is very short. (Stress or other problems can sometimes cause a cycle to be shorter or longer). If a woman has sex with a man during this time and conception occurs (his sperm fertilizes the egg), she becomes pregnant.
  • The fertilized egg attaches to the uterus, and the corpus luteum makes all the progesterone needed to keep it implanted and growing until a placenta (an organ connecting the fetus to the mother) develops. The placenta then makes hormones and provides nourishment from the mother of the baby.
  • If an egg is not fertilized that month and the woman doesn’t get pregnant, the corpus luteum stops making hormones and gets reabsorbed in the ovary. Hormone levels drop again, the lining of the uterus breaks down, menstruation begins, and the cycle repeats.


  • More than half of menstruating women have cramp-like pain during their periods. The medical term for menstrual pain is dysmenorrhea.
    · Cramps are usually felt in the pelvic area and lower abdomen, but can radiate to the lower back or down the legs.
    · Many girls have cramps severe enough to keep them home from school. Dysmenorrhea is the most frequent cause of absenteeism from school among younger women.
    · Women seem to go through phases when cramps are severe, then get better for several years, and then maybe worsen again. Most women find they have less menstrual pain after having children.
  • Mechanically, cramps are like labor pains. Just as the uterus contracts to open up the cervix (neck of the uterus) and push out a baby, it contracts to expel menstrual blood. Often, after several years of menstruating or after childbirth, the cervical opening enlarges. The uterus doesn’t have to contract as much to discharge the menstrual flow, so there is less cramping.
  • Menstrual pain may also come from the bleeding process itself. When the uterine lining separates from the wall, it releases chemicals called prostaglandins. Prostaglandins cause blood vessels to narrow, impending the supply of oxygen to the uterus. Just as the pain of a heart attack comes from insufficient blood to the muscles of the heart, too little blood to the uterine muscle might cause the pain of menstrual cramps. Menstrual pain can have other causes including tumors, fallopian tube infection, and endometriosis, a condition in which fragments of the lining of the uterus become embedded elsewhere in the body.


  • Sometimes, simple measures are all that’s needed to feel better. Cutting down on salt might help reduce fluid buildup, and support hose may alleviate swelling in the legs or ankles. Extra rest or sleep is one way to deal with fatigue, and using a heating pad or hot water bottle eases cramps for some. Exercising also helps reduce pain in many young women, and may lift a blue mood as well.
  • Exercising during menstruation lessen pain because it causes release of brain chemicals called endorphins, which are natural painkillers. Exercise may also decrease pain by affecting prostaglandin metabolism. Exercise may also decrease pain by affecting prostaglandin metabolism. Exercise may also help because it increases blood flow, and because it makes a lot of people feel better in general.