The menstrual cycle is a natural process that happens in most girls and women every month. It’s the body’s way of preparing for a possible pregnancy. If a woman doesn’t become pregnant, her body removes the extra tissue it had built up — and this comes out as bleeding from the vagina, known as a period.
This cycle is controlled by hormones and usually starts during puberty (around the age of 11 to 14) and continues until menopause (usually around age 45 to 55). While every woman’s cycle is different, understanding how it works can help you take better care of your health and well-being.
Definition:
The menstrual cycle is a monthly cycle of physical and hormonal changes in a woman’s body that helps prepare for pregnancy. It starts with the first day of a woman’s period and lasts until the day before her next period.
During this time:
- The body grows and releases an egg (this is called ovulation).
- The lining of the uterus (womb) becomes thick to support a pregnancy.
- If the egg is not fertilized, the lining is not needed — so the body sheds it, which causes the period.
A typical menstrual cycle is about 28 days, but it can be as short as 21 days or as long as 35 days, and that’s perfectly normal.
Phases of the Menstrual Cycle
The menstrual cycle is divided into four phases. Each phase plays a special role in preparing a woman’s body for pregnancy. If pregnancy doesn’t happen, the cycle starts again. Let’s go through each phase step-by-step in a simple way.
1. Menstrual Phase (Days 1 to 5)
This is the phase when you get your period.
During this time, the body removes the thickened lining of the uterus that was not needed. This lining comes out of the body through the vagina as blood. That’s what we call a period.
Hormone levels like estrogen and progesterone are low at this point, which is what causes the bleeding. Some common symptoms during this time include stomach cramps, back pain, tiredness, and mood swings. Periods usually last between 3 to 7 days.
2. Follicular Phase (Days 1 to 13)
This phase actually starts on the same day as your period but continues after the bleeding ends.
Here’s what happens: your brain sends a signal to your ovaries to start growing tiny sacs called follicles. Each follicle contains an immature egg. One of these eggs starts growing more than the others — this is the one that will be released later during ovulation.
At the same time, estrogen levels slowly rise. This helps rebuild the inner lining of the uterus so that it can be ready to support a baby if fertilization happens.
You may start feeling more energetic, positive, and focused during this time.
3. Ovulation Phase (Around Day 14)
Ovulation is the moment when the mature egg is released from the ovary.
This happens because of a sudden rise in a hormone called LH (luteinizing hormone). The egg travels through the fallopian tube and waits for sperm to fertilize it. This is the most fertile time of your cycle — the best time to get pregnant if you’re trying.
Some women can feel mild pain in their lower belly, notice a stretchy clear discharge, or feel more attraction toward their partner. These are signs that ovulation is happening.
4. Luteal Phase (Days 15 to 28)
This is the final phase of the cycle, right after ovulation.
The follicle that released the egg turns into something called the corpus luteum, which now produces progesterone. This hormone makes the lining of the uterus thick and soft — just in case the egg gets fertilized.
If the egg does get fertilized, your body will continue making progesterone to support the early stages of pregnancy.
If the egg is not fertilized, progesterone levels will drop. This causes the lining of the uterus to break down and come out — and the cycle starts again with your next period.
You may feel changes in your mood, bloating, tender breasts, or cravings — these are common PMS (premenstrual syndrome) symptoms.
Chart Summary of the Phases:
| Phase | Days | What Happens | Main Hormones Active |
|---|---|---|---|
| Menstrual | 1–5 | Uterus lining sheds (period) | Low estrogen and progesterone |
| Follicular | 1–13 | Egg matures, lining starts to rebuild | Rising estrogen |
| Ovulation | ~14 | Egg is released | LH (luteinizing hormone) |
| Luteal | 15–28 | Body prepares for pregnancy | Progesterone |
Hormones
The menstrual cycle is more than just a monthly period — it’s a well-organized process controlled by hormones. These hormones act like messengers between your brain and reproductive organs, helping the body prepare for a possible pregnancy.
Let’s break down the four main hormones involved in the menstrual cycle and understand what each one does.
1. Follicle-Stimulating Hormone (FSH)
Produced by: Pituitary gland (in the brain)
Main job: Helps eggs grow inside the ovaries
At the beginning of the menstrual cycle, your brain releases FSH. This hormone travels to the ovaries and signals them to start developing tiny sacs called follicles. Each follicle holds an immature egg, and FSH helps one of them grow larger and stronger to get ready for ovulation. This phase is the start of preparing the body for a possible pregnancy.
2. Luteinizing Hormone (LH)
Produced by: Pituitary gland
Main job: Triggers ovulation (egg release)
Around the middle of the cycle, there’s a sudden increase in LH levels. This is called the LH surge. It’s what causes the mature egg to be released from the ovary — a process known as ovulation. After the egg is released, LH also helps in forming the corpus luteum, a temporary structure that produces the hormone progesterone in the second half of the cycle.
3. Estrogen
Produced by: Ovaries
Main job: Rebuilds the uterine lining and supports egg development
As the egg develops during the first half of the cycle, estrogen levels begin to rise. Estrogen plays a big role in thickening the lining of the uterus, making it ready to support a fertilized egg. It also helps improve mood, energy levels, and skin health, which is why many women feel their best in the days leading up to ovulation.
Estrogen has another small rise during the second half of the cycle but is most active before ovulation.
4. Progesterone
Produced by: Corpus luteum (in the ovary after ovulation)
Main job: Maintains the uterine lining and supports early pregnancy
After ovulation, progesterone becomes the key hormone. It keeps the uterine lining thick and stable, just in case the released egg gets fertilized. If pregnancy happens, progesterone continues to rise to support it. If not, progesterone levels drop — and this drop is what causes the period to begin.
Progesterone is also the hormone behind many PMS symptoms like bloating, tender breasts, and mood swings.
Hormone Chart
| Hormone | Released By | What It Does |
|---|---|---|
| FSH | Pituitary gland | Stimulates egg development in ovaries |
| LH | Pituitary gland | Causes ovulation (egg release) |
| Estrogen | Ovaries | Thickens uterine lining, boosts mood & energy |
| Progesterone | Corpus luteum | Maintains uterine lining, supports pregnancy |