Exploring the Phases of the Menstrual Cycle


The menstrual cycle is a biological process of the female reproductive system. It is controlled by hormones. The monthly menstruation or ‘period’ as we call it, is a part of this cycle.

What is the Menstrual Cycle?

Menstrual cycle begins with shedding of the uterine walls or period. A follicle is developed to release an ovum or mature egg that will reach the fallopian tube to be fertilized. During this time, the uterus’s inner wall starts building up again for a possible pregnancy.

If the egg isn’t fertilized by sperm,there will be no pregnancy. The thick uterus wall loses purpose and starts shedding which begins another period and another menstrual cycle.

The cycle duration varies from woman to woman and can even be different lengths for one woman too. A menstrual cycle lasts for 21-35 days with 28 days being the average. While the menstrual cycle may seem complex to understand, it can be broken down into four phases for a clearer picture.

PhaseStarts and Ends On (Day)
Menstrual phase1-5
Follicular phase1-13
Ovulation phase14
Luteal phase15-28
Note: This chart shows phases of a 28-day menstrual cycle.

It’s important to understand that ‘menstruation’ and ‘menstrual cycle’ are not the same thing. There’s a misconception that menstruation and menstrual cycle are interchangeable terms but that is not true. Menstruation is the bleeding itself while the menstruation cycle comprises all four stages. All phases play important roles in maintaining your reproductive health.

Menstrual Phase

The first phase is the menstruation or period. This is the bleeding stage that we are all familiar with. The new period and the new cycle begin on the same day. Its duration can vary from person to person, from 2-7 days with 5 being the average length.

Duration: 2-7 days

Average: 5 days


  • Estrogen ↓
  • Progesterone ↓


Period symptoms usually show up 4-7 days before the period begins. These symptoms are great indicators of the approaching period.

  • Bloating
  • Cramps
  • Mood swings
  • Acne
  • Sensitive breasts
  • Sluggishness
  • Backache & more

What Happens during Menstruation?

If the egg from the last cycle is not fertilized, there will be no pregnancy. When this happens, the thick lining of the uterus has no need to exist. There is a drop in estrogen and progesterone from the previous luteal phase.

Therefore, the lining starts to shed and it comes out of the vagina. This is what we call ‘period’.

The period blood consists of blood, tissues of the uterus lining, and mucus. During this time, it’s common to use sanitary products, such as pads, tampons, menstrual cups, and more, to take in the shedding blood.

A person bleeds 60 ml or four tablespoons on average during their period. You can also bleed 30-40 ml during a lighter period but if it exceeds 80 ml, that’s a matter of concern.

Follicular Phase

The second phase is the follicular phase. The start of this section overlaps with menstruation as it also begins from Day 1 of the cycle. This phase can last from 10-21 days. It varies with every cycle. However, the usual duration is 13-16 days. It happens in the ovary.

Duration: 10-21 days

Average: 14 days


  • Follicular Stimulating Hormone (FSH) ↑
  • Estrogen ↑


  • Increased energy
  • Better concentration

What Happens in the Follicular Stage?

Your brain has a section called Hypothalamus. It is the connecting force between your endocrine system (hormone system) and the nerves.

Hypothalamus signals the pituitary gland to release Follicular Stimulating Hormone (FSH). Just as the name suggests, this hormone ‘stimulates’ or triggers your ovaries to mature the follicles.

Follicles are small sacs filled with fluid and they contain immature eggs. These eggs are unfertilized.

Did you know women are born with all their eggs and ovarian follicles? They remain latent until you start puberty and then start developing. Only one-fourth of the follicles remain once you start puberty. They decrease over time.

Only one ovary will release follicles, usually 5-20 in quantity. The follicle with the healthiest egg will become the dominant one and only this egg will mature. The other follicles will decay and be absorbed into the ovary. This usually happens on Days 10-13.

The process of follicle maturing triggers a rise in estrogen. This hormone starts thickening the endometrium (inner uterus wall) for pregnancy preparation.

Ovulation Phase

The third phase is Ovulation phase, which is the most crucial part if you’re trying to conceive. In this phase, the ovary finally releases a mature egg or ovum ready to be fertilized.

Duration: 12-36 hours

Average: 24 hours


  • Luteinizing Hormone (LH) ↑
  • Estrogen ↑


  • Small rise in basal body temperature
  • Transparent, stretchy, and wet vaginal discharge (almost egg-white texture)
  • Mild cramps
  • Mild pelvic pain
  • Sensitive nipples

What Happens during Ovulation?

The surge of estrogen in the follicular phase signals the pituitary gland to release a hormone called Luteinizing Hormone (LH) which triggers the next phase, Ovulation.

On the 14th day of the 28-day cycle, there is an increase in LH that results in the follicle bursting and releasing the matured egg. Ovulation happens usually 2 weeks or 14 days before the next menstruation phase. If you have a 32-day cycle, the slight increase in LH and ovulation might happen on the 19th day.

But, it might not always happen two weeks before your next period. The time might vary during each cycle. The general time is 13-20 days before your next period.

This ovum will travel through the fallopian tube to get to the uterus. During its time in the fallopian tube, the egg is ready to be fertilised by a sperm. This is when pregnancy takes place.

The egg is active for 12-36 hours in the fallopian tube with 24 hours being the average lifespan. This small window is called the Ovulation phase.

The sperm can live up to 5 days inside the tube. So, having intercourse a few days before the ovulation face can result in the sperm staying in the fallopian tube for some time until the mature egg is released.

This means that having intercourse without protection before your ovulation can result in pregnancy as well. You are most likely to become pregnant by having intercourse three days before and on the day of your ovulation.

If during the 36 active hours of ovulation, the egg is fertilized by sperm, there will be pregnancy. On the other hand, if there is no fertilization, there will be no pregnancy, and the egg will start to dissolve.

Luteal Phase

The luteal phase is the fourth and last phase of the menstrual cycle. In a 28-day cycle, it starts on the 15th day. It generally begins two weeks before the next cycle and period. The average duration is 14 days.

Duration: 14 days

Average: 14 days


  • Luteinizing Hormone (LH) ↑
  • Progesterone ↑
  • Estrogen ↑
  • Follicular Stimulating Hormone (FSH) ↓

If Fertilization Happens:

  • Human Chorionic Gonadotropin (hCG) ↑
  • Progesterone ↑
  • Estrogen ↑

If No Fertilization Happens:

  • Progesterone ↓
  • Estrogen ↓
  • Follicular Stimulating Hormone (FSH) ↑


In the luteal phase, you will start PMS-ing or show premenstrual symptoms.

  • Mood swings
  • Sensitive breasts
  • Bloating
  • Cramps
  • Sudden craving
  • Fluctuation of energy
  • Tiredness and less sleep

What Happens in the Luteal Phase?

The egg reaches the uterus, after traveling through the fallopian tube. If fertilized, the egg will implant into the uterus lining and start growing. But, if the egg is unfertilized, it will start to break down.

So, what happens to the follicle from which the egg bursts out? It transforms into a corpus luteum and releases progesterone and small amounts of estrogen. These hormones also contribute to further thickening the uterus lining which started in the follicular phase. The FSH that was released during the follicular phase gets blocked by progesterone.

If pregnancy takes place, the body will release Human Chorionic Gonadotropin (hCG). When you take a pregnancy test, the test detects the presence of hCG to know if you’re pregnant or not.

The corpus luteum will continue to produce progesterone to thicken the uterine wall more. It will produce progesterone for the next 3 months to support pregnancy.

However, in the case of no fertilization, the corpus luteum will start to disintegrate after 14 days. Therefore, progesterone level falls naturally as well. Since there are low levels of progesterone and estrogen, FSH starts increasing again. Your uterus lining will start to shed again. Another period starts and so does a new cycle.

To conclude, the menstrual cycle is completely managed by hormones. A healthy and stable menstrual cycle indicates the good condition of our reproductive system. However, if you suffer from fluctuating cycles, it’s best to consult a doctor.

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