What are the different phases of a period cycle?

Overview of the menstrual cycle

The menstrual cycle is measured from the first day of your period to the day before your next period. On average, a period cycle is 28 days. However, everyone’s cycle is different and some women may have shorter cycles of around 21 days or even longer cycles of up to 35 days.

There are three phases of a period cycle, with each phase involving distinct hormonal and biological changes.

The cycle begins with menstruation where the lining of the uterus is shed. This also marks the first day of the follicular phase. This phase lasts until ovulation occurs, which is typically around the middle of the cycle. Following ovulation, the luteal phase begins, lasting until either pregnancy occurs or menstruation starts again.

What are the three phases of the menstrual cycle

1. Follicular phase

The follicular phase is the first stage of the menstrual cycle. It begins on the first day of menstruation and lasts for 13 or 14 days until ovulation. During this time, the hypothalamus (an area of the brain that produces hormones) releases a hormone called gonadotropin releasing hormone (GnRH). This stimulates the pituitary gland (a pea-sized gland located at the base of your brain) to produce follicle-stimulating hormone (FSH).

FSH encourages the ovaries to produce follicles (small sacs that contain and nurture eggs). Towards the end of the follicular phase, FSH levels decrease and only one follicle (dominant follicle) continues to grow. This follicle starts to produce oestrogen which plays a crucial role in preparing the uterus to support a fertilised egg by causing the lining of the uterus (endometrium) to thicken. At the same time, levels of luteinising hormone begin to increase.

2. Ovulation

Ovulation marks the second phase of the menstrual cycle. Ovulation begins when levels of luteinising hormone surge. This causes the dominant follicle to rupture from the ovary and release an egg. Ovulation usually occurs around the 14^th day of a 28-day cycle, and lasts 16 to 32 hours. It usually happens every month, about two weeks before a period. The egg travels down the fallopian tube, where it remains viable for about 24 hours, awaiting fertilisation by sperm.

3. Luteal phase

The luteal phase is the final phase of the period cycle, lasting from ovulation until your period begins (about 14 days), unless the egg is fertilised. Following ovulation, the ruptured follicle transforms into what’s called the corpus luteum — a structure that secretes progesterone. This hormone causes the lining of the uterus and mucus of the cervix to thicken even further, in preparation for pregnancy. Levels of oestrogen are also high at this time, which further contributes to the thickening of the uterine lining.

If pregnancy does not occur, the corpus luteum degenerates, leading to a decline in progesterone and oestrogen levels. This hormonal change causes the uterine lining to break down and shed, resulting in you having your period.

Periods can last anywhere between three and seven days and contain blood, mucus, and cells from the lining of the uterus.

What physical changes might you notice during the different phases of your menstrual cycle?

Throughout the menstrual cycle phases, the release and regulation of hormones lead to noticeable physical changes and symptoms in your body.

During the follicular phase, you may notice increased energy, better mood, and feel that you can think more clearly. This is due to increased levels of oestrogen.

Around the time of ovulation, you may notice changes in your cervical mucus. At this time it’s normal for mucus to appear thick, clear, sticky and resemble the consistency of egg white. These changes to the cervical mucus make it easier for sperm to swim to an egg after ovulation and is a sign that you’re most likely to conceive at this time. Changes to cervical mucus are due to the increase in progesterone levels.

In the luteal phase, you may experience physical symptoms such as bloating, breast tenderness, and mood swings due to changing progesterone levels.

Why it’s important to track your menstrual phases

Tracking the phases of your menstruation cycle can give you a better understanding of how your body changes throughout the month. Recognising your body’s natural patterns throughout the different phases of the menstrual cycle can help you more accurately pinpoint your fertile window and give you the best chance of conceiving naturally.

Tracking the phases of your period cycle can also help identify any health issues that may interfere with natural reproduction, such as polycystic ovary syndrome (PCOS) or thyroid problems.

Tracking the phases of your menstrual cycle

It can take a little while to fully understand your menstrual cycle and how each phase impacts you, but doing so will help you become more aware of your body and navigate your fertility journey.

To track your cycle effectively, be consistent in recording data. You can use apps or write down any changes you notice. We recommend you take note of:

• the date your period begins
• how many days your period lasts
• the days between the first day of one period and the first day of your next period
• changes in your mood, energy levels and other body signals throughout each phase
• changes to your cervical mucus over your cycle.

Over time, you’ll gain a greater understanding of how your cycle works, and the physical and emotional changes that changing hormone levels can have on you.

Understanding the phases of your menstrual cycle is vital to increase your fertility awareness and optimise your chances of conception. By tracking these phases, you can identify your most fertile days, making it easier to conceive naturally.

If conception remains challenging despite attentive cycle tracking, it may be helpful to seek the assistance of a fertility specialist. Having data on your menstrual cycle will help a specialist identify and address underlying conditions or hurdles in your fertility journey, and make for a more informed and supported experience.