The female menstrual cycle
Women have different menstrual cycles, but many facts apply to everyone.
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 female hormonal cycle when her uterus sheds its lining and the tissues and blood leave her body through the vagina.
Women have periods from puberty until menopause
Girls may start to have periods at any time between age eight and eighteen, during puberty.
Once a girl starts having periods, it may take her body some time to get adjusted. She may skip one or more periods during the first year. Eventually, her body will settle into a schedule and her periods will become more regular.
The first day of a woman’s period is said to be the first day of her menstrual cycle. The last day of her cycle is the last day before her 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 woman 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 woman 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 Health Sciences Centre)