Menstrual Cycle Explained: Phases, Ovulation, Periods & Fertility

The menstrual cycle is a monthly hormonal process that prepares a woman's body for pregnancy. It begins on the first day of a period and ends on the day before the next period starts. A normal menstrual cycle usually lasts between 21 and 35 days, with the average being 28 days. The cycle includes four phases: menstruation, follicular phase, ovulation, and luteal phase. Understanding your menstrual cycle can help with fertility planning, pregnancy awareness, and identifying reproductive health concerns.

What Is a Menstrual Cycle?

The menstrual cycle is a series of hormonal changes that occur every month in women of reproductive age.

Its primary purpose is to prepare the body for pregnancy.

During each cycle:

An egg develops inside the ovary
The uterus prepares for implantation
Ovulation occurs
If pregnancy does not happen, the uterine lining sheds as a period

The cycle then starts again.

What Is Menstruation?

Menstruation, commonly called a period, is the monthly shedding of the uterine lining.

During menstruation:

Blood
Uterine tissue
Cervical mucus

leave the body through the vagina.

A period is a natural part of the reproductive cycle and indicates that pregnancy did not occur during that cycle.

How Long Is a Normal Menstrual Cycle?

The average menstrual cycle is:

28 Days

However, cycles between:

21–35 Days

are considered normal for most adults.

Teenagers may experience slightly longer and more irregular cycles.

How Long Does a Period Last?

Most periods last:

3–7 Days

Some women may naturally have:

3-day periods
5-day periods
7-day periods

All can be normal if they occur consistently.

The Four Phases of the Menstrual Cycle

The menstrual cycle consists of four main phases.

1. Menstrual Phase

This phase begins on the first day of bleeding.

During this stage:

The uterine lining sheds
Menstrual bleeding occurs
Hormone levels are low

Typical duration:

3–7 Days

2. Follicular Phase

This phase overlaps with menstruation.

During the follicular phase:

Follicle-stimulating hormone (FSH) increases
Ovarian follicles begin developing
Estrogen levels rise
The uterine lining thickens

One dominant follicle eventually matures into an egg.

3. Ovulation Phase

Ovulation is the most fertile phase of the menstrual cycle.

Around the middle of the cycle:

Luteinizing hormone (LH) surges
The ovary releases a mature egg
The egg enters the fallopian tube

Most women ovulate approximately 14 days before their next period.

For a 28-day cycle, ovulation often occurs around Day 14.

For detailed fertility tracking, read our guide on Ovulation: Symptoms, Signs & Fertile Window.

4. Luteal Phase

After ovulation:

Progesterone levels rise
The uterus prepares for pregnancy
The egg travels through the fallopian tube

If fertilization does not occur:

Estrogen and progesterone decrease
The uterine lining breaks down
Menstruation begins again

Menstrual Cycle Timeline

Cycle Day	What Happens
Day 1–5	Menstrual bleeding
Day 6–13	Follicular phase
Day 14	Ovulation
Day 15–28	Luteal phase

The timing varies based on cycle length.

Common Symptoms During the Menstrual Cycle

Hormonal fluctuations can cause various symptoms.

Before or During Periods

Cramps
Bloating
Mood swings
Breast tenderness
Acne
Fatigue
Headaches
Food cravings

These symptoms are commonly known as PMS (Premenstrual Syndrome).

What Happens During Ovulation?

Ovulation is when a mature egg is released from the ovary.

Signs of ovulation may include:

Egg-white cervical mucus
Mild pelvic pain
Increased sex drive
Breast tenderness
Slight increase in body temperature

Ovulation is the most fertile time of the cycle.

Can You Get Pregnant During Your Menstrual Cycle?

Yes.

Pregnancy occurs when:

Sperm fertilizes an egg after ovulation

Because sperm can survive for up to five days inside the female reproductive tract, intercourse before ovulation can still result in pregnancy.

The highest chance of pregnancy occurs during the fertile window.

What Is an Irregular Menstrual Cycle?

A menstrual cycle may be considered irregular if:

Periods occur less than 21 days apart
Periods occur more than 35 days apart
Bleeding lasts longer than 7 days
Periods stop for 3 months or more
Cycle length changes significantly every month

Irregular cycles can affect fertility and may require medical evaluation.

Causes of Irregular Periods

Several conditions can disrupt menstrual cycles.

PCOD & PCOS

One of the most common causes.

Symptoms may include:

Irregular periods
Weight gain
Acne
Difficulty conceiving

Thyroid Disorders

Both hypothyroidism and hyperthyroidism can affect periods.

Stress

Chronic stress can interfere with hormone production.

Excessive Exercise

Overtraining can disrupt ovulation and menstruation.

Obesity

Hormonal imbalances linked to obesity may cause irregular periods.

Perimenopause

Women approaching menopause often experience irregular cycles.

When Should You See a Doctor?

Consult a specialist if:

Periods stop for more than 3 months
Bleeding is unusually heavy
Periods occur very frequently
Severe menstrual pain affects daily life
You experience difficulty getting pregnant
Cycles become consistently irregular

Early diagnosis often improves reproductive health outcomes.

Menstrual Cycle and Fertility

A healthy menstrual cycle is often a sign of regular ovulation.

Women with:

Irregular periods
Missed periods
Ovulation disorders

may experience difficulty conceiving naturally.

Tracking menstrual cycles helps identify fertility windows and reproductive health issues.

Fertility Care at Kiran Infertility Center

At Kiran Infertility Center, fertility specialists evaluate menstrual health, ovulation patterns, ovarian reserve, and hormonal balance to identify factors affecting conception.

Services include:

Women experiencing irregular cycles or fertility concerns can consult specialists at a trusted IVF Center in Delhi for personalized guidance.

Conclusion

The menstrual cycle is a complex but natural process that prepares the body for pregnancy each month. Understanding its phases, symptoms, and ovulation timing can help women manage reproductive health, improve fertility awareness, and identify potential health concerns early.

If you experience irregular periods, missed cycles, or difficulty conceiving, seeking professional evaluation can help identify underlying causes and provide appropriate treatment options.

With advanced fertility care and personalized treatment plans, Kiran Infertility Center, a leading IVF Center in Delhi, supports women through every stage of their fertility journey.

FAQs

What is the menstrual cycle?

The menstrual cycle is a monthly series of hormonal changes that prepares a woman's body for pregnancy. It begins on the first day of a period and ends the day before the next period starts.

What are the four phases of the menstrual cycle?

The four phases are the menstrual phase, follicular phase, ovulation phase, and luteal phase. Each phase plays an important role in fertility and reproductive health.

How many days does a normal menstrual cycle last?

A normal menstrual cycle typically lasts between 21 and 35 days, with 28 days being the average cycle length.

How long should a period last?

Most periods last between 3 and 7 days. However, some women may naturally have shorter or longer periods.

What happens during ovulation?

During ovulation, a mature egg is released from the ovary and enters the fallopian tube, where fertilization can occur if sperm is present.

When is the fertile window during the menstrual cycle?

The fertile window includes the five days before ovulation and the day of ovulation. This is the time when pregnancy is most likely to occur.

Can you get pregnant right after your period?

Yes. If ovulation occurs early and sperm survives in the reproductive tract, pregnancy can occur from intercourse shortly after a period ends.

Can you get pregnant during your menstrual cycle?

Yes. Pregnancy can occur if sperm fertilizes an egg during the fertile window of the menstrual cycle.

What causes irregular menstrual cycles?

Irregular periods can be caused by PCOS, thyroid disorders, stress, obesity, excessive exercise, hormonal imbalances, or perimenopause.

Can PCOS affect the menstrual cycle?

Yes. PCOS is one of the most common causes of irregular or missed periods and can also affect ovulation and fertility.

Can stress delay periods?

Yes. Chronic stress can affect hormone production and disrupt ovulation, which may lead to delayed or irregular periods.

Does thyroid disease affect menstrual cycles?

Yes. Both hypothyroidism and hyperthyroidism can cause changes in menstrual flow, cycle length, and ovulation patterns.

What are common symptoms before a period?

Common premenstrual symptoms include cramps, bloating, mood swings, breast tenderness, fatigue, headaches, acne, and food cravings.

What is PMS?

Premenstrual Syndrome (PMS) refers to physical and emotional symptoms that occur before a period, often due to hormonal changes.

Is it normal to have irregular periods during puberty?

Yes. Menstrual cycles are often irregular during the first few years after periods begin because hormone levels are still stabilizing.

Can irregular periods affect fertility?

Yes. Irregular periods may indicate ovulation problems, which can reduce the chances of natural conception.

What is the difference between menstruation and ovulation?

Menstruation is the shedding of the uterine lining, while ovulation is the release of a mature egg from the ovary.

When should I see a doctor about irregular periods?

You should consult a doctor if your periods are consistently irregular, absent for several months, unusually heavy, or associated with severe pain.

Can menstrual cycle tracking help with pregnancy planning?

Yes. Tracking your cycle can help identify ovulation, fertile days, and potential reproductive health concerns.

Is a 21-day or 35-day cycle normal?

Yes. Menstrual cycles ranging from 21 to 35 days are generally considered normal for most adult women.

Menstrual Cycle: Phases, Symptoms, Ovulation & Fertility Explained