The Four Phases of the Normal Menstrual Cycle

By Ashley Danielle
Edited by Taj Schlebusch

Published September 23, 2021.

The Four Phases of the Normal Menstrual Cycle main image

Most women's bodies will go through a number of changes between the years of puberty and menopause to get ready for a possible pregnancy. Once sexually mature, the monthly recurrence of hormonal changes is known as an estrous cycle, more commonly called the menstrual cycle. Each cycle is divided into 4 stages, the average 'normal' duration of each cycle is 28 days.

Below we will discuss each phase and its conditions.

The Menses Phase (Menstruation)

The 'Menses' menstrual phase is the first stage of the menstrual cycle. This is what we officially call "getting your period." During each menstrual cycle, an egg develops and is released from the ovaries.

During this time the lining of the uterus, also known as the endometrium, builds up. If a pregnancy doesn’t happen, the uterine lining will shed, and this is what we call 'menstruation'. On average, a woman's menstrual phase lasts for about 3 to 7 days. But it is not uncommon for some women to have longer periods.

During this time it is common to use things like tampons, pads, or menstrual cups to catch or absorb the menstrual fluid. However, when choosing which to use we need to consider the possible side effects of each. For example, wearing a tampon for prolonged periods at a time (more than 8 hours) may cause infections or toxic shock syndrome (TSS).

The Follicular Phase

The follicular phase actually begins on the first day of your period, so there is some overlap with the menstrual phase. During this phase, your pituitary gland will release the follicle-stimulating hormone (FSH).

This hormone stimulates your ovaries to produce around 5 to 20 small sacs called follicles. Each follicle contains an immature egg and only the healthiest egg will eventually mature. The maturing follicle sets off a surge in oestrogen that thickens the lining of your uterus. The average follicular phase can last about 16 to 27 days, depending on your cycle.

Although you are not technically ovulating during the follicular stage, it is still possible to get pregnant.

Ovulation

Ovulation is the phase of menstruation when the ovaries release a mature egg. The egg will travel down the fallopian tube to the uterus awaiting to be fertilized by sperm. Rising oestrogen levels during the follicular phase will trigger the pituitary gland to release the 'luteinizing hormone' (LH) and begin the ovulation process.

The ovulation phase is the optimal time during your menstrual cycle to get pregnant. Ovulation will happen around day 14 if you have a 28-day cycle. Essentially ovulation happens right in the middle of your menstrual cycle and only lasts about 24 hours. After a day, the egg will die or dissolve if it isn’t fertilized.

Luteal Phase

The luteal phase occurs after ovulation and before your period starts. After the follicle releases its egg, it changes into something called the 'corpus luteum'. This structure releases progesterone and some oestrogen. This rise in hormones will keep the uterine lining thick and ready for a fertilized egg to implant. If pregnancy occurs, the body will produce 'human chorionic gonadotropin', which helps maintain the corpus luteum and in turn, keeps the uterine lining thick.

If no pregnancy occurs, the corpus luteum will shrink away and be reabsorbed. This process leads to decreased levels of oestrogen and progesterone and causes the onset of your period. At this point, you will start to feel the traditional symptoms of PMS. The luteal phase, on average, is about 12 to 14 days long.

Conclusion

It’s important to get familiar with your cycle, you can use an app or a journal to keep track. Make sure to document the duration times and symptoms of each phase. Be sure to report any alarming changes to your doctor. Remember, every woman's cycle is different, what is 'normal' for some may not be 'normal' for you.