Sexuality and U

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All about the menstrual cycle


What is the menstrual cycle?

The menstrual cycle is just that: a cycle. It is your body’s way of preparing itself for a possible pregnancy. A girl’s cycle is the length of time it takes her body to go through the process of releasing an egg, preparing the uterus to cushion a fertilized egg, and then shedding the thickened lining and the unfertilized egg (by bleeding that comes out of the vagina).  The “period” itself is part of this cycle. Your hormone system controls your menstrual cycle. The changes in your body (including cramps, moodiness and your period) are brought on by changes in the levels of hormones that are running through your system. The medical term for getting your period is menstruation or menses. 

What happens during the menstrual cycle?

As you enter puberty your body starts to change. Your breasts develop; you start to get pubic hair and hair under your arms; a few months before your first period you may even notice that you have a clear discharge from your vagina. Don’t panic! This is all normal.

About once a month, an egg leaves the ovaries and travels down the fallopian tubes towards the uterus. At the same time, the lining of the uterus becomes thicker with extra blood and tissue to make a cushion for a potentially fertilized egg. If an egg is fertilized with sperm and you become pregnant, the fertilized egg will attach itself to your uterus where it will slowly develop into a baby. If the egg is not fertilized, the lining of the uterus begins to break down so it can be shed (along with the egg that was not fertilized). Your period – or the time of bleeding – happens when your body gets rid of the extra blood and tissue that’s no longer needed. Then the cycle starts all over again.

Remember, you can still get pregnant if you have unprotected sex while you are menstruating. And if you are having sex without birth control and you don’t get your period for a month or longer, you could be pregnant.   

How long does a cycle last?

A cycle usually lasts about 28 days, but it can range anywhere from 21 to 36 days. The length of a cycle varies from woman to woman. The first day of your period is called Day 1 of your cycle. Your cycle is counted from the first day of bleeding in one month to the first day of bleeding in the next month. For example, if your period starts on the 1st of the month, you have 5 days of bleeding, and then you don’t have another period until the 30th of the month, then you would say that you have a 29 day cycle. Honest, it’s not that confusing!

When a young woman starts to menstruate, it usually takes a few years for her body to fall into a regular pattern of menstruation. It is normal for her cycle to be a little off schedule for the first few years. In the years leading up to menopause (when a woman stops ovulating and her period stops) a woman’s cycle may also be a bit unpredictable. During this time, menstruation may actually last a shorter period of time and the time between periods may be longer.

Phases of the cycle

 Phases of egg maturation diagram adult woman EnglishLining of the uterus 3 diagrams English







menstrual cycle only diagram 6 steps English


There are three basic phases to the cycle:

Phase 1 Ripening (or the follicular phase): First, an egg starts ripening in your ovaries. At the same time the hormone called estrogen triggers the lining of your uterus (the endometrium) to thicken with blood and tissue in order to make a “cushion” for a potentially fertilized egg (an egg that has been fertilized by sperm). This happens during the first 14 days or so of your menstrual cycle. However, the process can be longer or shorter and each woman is different.

  • The last 5 days of the follicular phase, plus your ovulation day are when you are most likely to become pregnant if you have sex without using some form of birth control.
  • With ovulation, some women feel a bit of lower pelvic pain or have a tiny bit of red vaginal spotting. This is normal.

Phase 2 Premenstrual (or the luteal phase): When the egg is ripe, it leaves the ovary and starts traveling down the fallopian tubes. This is called ovulation and happens about 14 days after the last day of your period. During this time the hormone progesterone helps the estrogen keep the lining of your uterus thick and ready to receive a fertilized egg. If the egg is not fertilized (if it doesn’t hook up with active sperm), then the levels of the hormones that helped to thicken the lining of your uterus (progesterone and estrogen) drop, causing the lining to break down so that it (and the egg that was not fertilized) can be shed from your uterus. This is the end of the premenstrual period and the beginning of your period.

  • The premenstrual period can happen any time from Day 7 to Day 22 of a normal menstrual cycle.
  • It usually lasts about 13 to 15 days (from ovulation to the first day of your period).
  • Most women have premenstrual symptoms of one kind of another. These include emotional symptoms – such as feeling angry, irritable, depressed or anxious – and physical symptoms – such as tender breasts, bloating, headaches or pimples.
  • Sometimes these symptoms are so strong that they make normal day-to-day living difficult. This could be a sign of PMS (premenstrual syndrome) and you might want to make an appointment with your doctor to talk about treatment options that will help you.

Phase 3 Menstruation: This is the day you start to bleed. It is when the thickened lining of the uterus begins to shed that you have menstrual bleeding from your vagina. This is Day 1 of your cycle. While it may seem strange call this Day 1 – because it’s the end of the whole process – it is the only day that is easy to mark. A ripening egg or ovulation does not have any visible signs that are easy to track or notice. So the beginning of your period marks Day 1 of your cycle.

  • Menstruation, or bleeding, can last from 2 to 7 days.
  • Most of your menstrual blood loss happens during the first 3 days.
  • This is also when you might have cramps and pain in your pelvis area, legs and back. This is because your uterus is contracting to help get rid of the lining. Cramps can be mild or severe.
  • If your period seems too heavy and painful, you may want to see your doctor or ask a pharmacist to suggest an over-the-counter medication.
What is normal?

A “normal” menstrual cycle can be very different for different women. “Normal” can also change depending on your age. Long or unpredictable menstrual cycles are normal for teenagers and women in their 40s. During your period, you usually only lose a small amount of blood – even though it might look and feel like a lot. You usually only lose from a few spoonfuls of blood to a half a cup. Menstrual blood often looks different from blood from a cut. It is often a deeper colour (sometimes brownish-red) and thicker.

If you haven’t started your period by the time you are 16, talk to your doctor.  If you are not a teenager or older than 40 and your cycles are shorter or longer than 21 to 36 days, it could be that you have an underlying problem and you should consult your doctor or a health-care professional.

If you experience any big changes in your cycle or in the amount of bleeding or pain (or other symptoms) that go with your period you should talk to a health care professional. Some signs to look for include:

  • Menstrual bleeding for 3 or more cycles that:
  • lasts longer than 7 days.
    • Is heavier than normal (if, for example, you are passing large clots or soaking a large pad or tampon every one or two hours).
    • Bleeding between menstrual periods.
      • Pain in the pelvic area that is not linked to menstrual bleeding and lasts longer than a day.
      • Emotional or physical symptoms (cramps, nausea, depression, irritability) that interfere with your daily life and are linked to your cycle.
      • your period is late (and usually isn’t) or you haven’t had a period for more than 6 months.
      • you think you might be pregnant
 Keeping a calendar

Calendar diagram

You can use a calendar to track your cycle. This helps you predict when your period is going to start (so you can be prepared), or when it should start (so you can talk to your doctor about any changes or the possibility of pregnancy). The easiest way to do this is to just use your regular calendar and mark a red P or a dot for the first day of your period. If you have settled into a regular cycle it should be easy for you to count the number of days (i.e., 28) and then pencil in when you will be expecting your next cycle to start. You might also want to keep a more detailed calendar that includes the day of your last period and any symptoms you experience during your cycle – such as tender breasts, cramps, headaches, backaches, moodiness, acne, difficulty sleeping, tiredness, bloating or an upset stomach. Keeping a calendar will help you know when something is not quite right. It will also help you talk to your doctor or other health-care professionals about your symptoms.