On average, girls in North America begin menstruating between the ages of twelve and thirteen. The onset of menstruation can happen as early as age nine and as late as 17. Estrogen, a hormone made in the ovaries, makes a girl's breasts start to bud (the area around the nipple starts to rise). About two years later, she will get her first period. Estrogen also makes the uterus change, producing a thin, odorless vaginal discharge. During the first two years of menstruation, the ovaries do not usually release any eggs. Periods are irregular and it is not uncommon to have only one or two a year. Periods become more regular over the next five years.

What happens during menstruation?

About once a month, one of the ovaries releases an egg. The egg travels into the fallopian tube connecting the ovary to the uterus. For a short time, the ovary produces hormones which make the lining of the uterus thicken. If the egg unites with a sperm in the fallopian tube, it will travel through the tube into the uterus. The fertilized egg then implants or buries itself in the thick, nourishing lining of the uterus. The fertilized egg makes a placenta which takes over hormone production from the ovary. Nine months later, a baby will be born.

If there are no sperm the egg remains unfertilized on its trip through the fallopian tube. It does not implant into the lining of the uterus or produce a placenta. The ovary eventually stops producing hormones. The thickened lining of the uterus is not needed, so it is cast off. The shedding of the lining through the vagina (birth canal) is called menstruation. The average menstrual cycle takes about 28 days from start to finish.

Myth 1A woman loses a lot of blood during menstruation.

Fact - The actual amount of blood normally lost during each cycle is only 28 to 80 millilitres in total (11⁄2 - 5 tbsp). This equals 10 to 15 saturated tampons or pads per cycle, with no more than six per day. Bleeding is heaviest during the first few days, and then tapers off rapidly. If you feel you are bleeding more heavily, talk to your doctor. There are several ways to decrease heavy bleeding during your period.

Myth 2It is impossible to get pregnant when you are menstruating.

Fact - It is rare but possible to get pregnant while menstruating. Some women have very short cycles, and can actually ovulate (release an egg) while still shedding the lining of the uterus. If pregnancy is not desired, it is always necessary to use a condom or other method of birth control during intercourse. There is only a small chance of this happening in women who take the pill regularly and as directed by their doctor.

Myth 3Virgins cannot use tampons.

Fact - A tampon is a soft, absorbent cotton wand. It is inserted into the vagina and soaks up blood as the lining is shed. Many people think that inserting a tampon will tear the hymen (membrane) in front of the opening to the vagina. In ancient times, an undamaged hymen was considered proof of virginity. The hymen is usually torn when a woman first has sexual intercourse. However, it can be broken in other ways, such as riding a horse or falling off a bike. Inserting a tampon will not rupture the hymen, since a tampon is smaller and softer than an erect penis.

Myth 4I always have painful periods. Nothing can be done about it.

Fact - Menstrual cramps are caused by contractions of the muscle in the wall of the uterus. It is common for cramps to accompany menstruation once it is well-established (after the first two years). Your body makes prostaglandin, a hormone which stimulates the uterus to contract. Going on the birth control pill or taking antiprostaglandin medications such as ibuprofin or naproxen can lessen cramps. Your doctor can help.

Myth 5 It isn't safe to exercise during a period.

Fact - Exercise during your period is safe. Some women find that regular exercise before and during a period reduces cramps, increases energy and improves mood. You should be able to carry on your normal activities while menstruating.

Myth 6 It isn't safe to have sex when a woman is menstruating.

Fact - You are at the same risk for sexually transmitted diseases (STDs) during menstruation as at any other time of the month. If either partner has an STD, the mentrual blood can make it easier to transmit. You should always use a condom for protection whether menstruating or not.

Myth 7 Menstrual blood is dirty.

Fact - Menstrual blood is the lining of the uterus which has been shed. This lining builds up every month to nourish a fertilized egg. It is not dirty; it is a normal body function. The blood will develop an odour when exposed to air. Frequent changes of tampons or pads can help prevent odours.

At times, it can be very sensitive to talk about menstrual problems. Your family doctor can be a reliable resource, providing a comfortable private environment to discuss questions and concerns. Knowing the facts about menstruation can help make it a normal part of every woman's life.

Menstrual Myths What's true, what's not