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The menstrual cycle

Menstruation is also called:

  • menses
  • having your period
  • the rag
  • that time of the month
  • bleeding
  • many other nicknames!

Menstruation is the part of the hormonal cycle when the uterus sheds its lining and the tissues and blood leaves the body through the vagina.

Periods begin in puberty and last until menopause

Periods may begin at any time between age eight and eighteen, during puberty.

Once a person starts having periods, it may take the body some time to get adjusted. You may skip one or more periods during the first year. Eventually, your body will settle into a schedule and your periods will become more regular.

The first day of a  period is said to be the first day of her menstrual cycle. The last day of the cycle is the last day before the period starts again.

  • Sweet Secrets has more information about first periods and puberty for girls

Periods last a few days per monthly cycle

The whole menstrual-ovulatory cycle usually takes about one month from one period to the next. The average cycle length is 28 days but it can range on average from about 23 – 35 days.

Each period usually lasts between two to eight days. All of these lengths, or anything in between, are normal for periods.

The menstrual cycle has several phases

These day counts are based on a stylized 28-day cycle, which is about the middle length that a menstrual cycle can be.

Day 1: bleeding starts

  • hormone levels are at their lowest
  • lining of the uterus is released from the body as menstrual blood
  • the unfertilized ovum (egg) produced in the last cycle is also shed

Day 2 – 12: menstruation

  • Menstruation (the period) continues for three to six days for most women
  • When menstruation begins, a new egg begins to mature in the ovaries
  • Increasing hormone levels prompt the uterine lining to thicken, beginning around day nine
  • If a person becomes pregnant this nutrient-rich lining supports the developing embryo

About day 14: ovulation

  • Ovulation (releasing of the egg) usually occurs about 14 days before the person gets her period.
  • However, ovulation is influenced by many factors, and has been known to occur any time during the cycle, even during the menstrual period.
  • Estrogen levels peak
  • Sac containing the mature egg splits open releasing it from the ovary; this is called ovulation
  • Lining of the uterus continues to get thicker

Day 15 – 22: luteal phase

  • The empty sac left in the ovary begins to produce both estrogen and progesterone; this sac is called the corpus luteum
  • The uterine lining continues to thicken due to estrogen produced by the ovary
  • The egg travels from the ovary down the fallopian tube
  • If the egg is going to be fertilized it is likely to happen now; when a fertilized egg reaches the uterus, high levels of estrogen and progesterone signal the uterine lining to allow it to implant on the wall of the uterus

Day 22 – 28

  • Around this time the ovaries stop producing estrogen and progesterone
  • If the egg has not been fertilized, levels of both estrogen and progesterone will begin to drop

Source: Women’s Health Matters Network (Sunnybrook and Women’s College)