The Menstrual Cycle

The Menstrual Cycle

The Menstrual Cycle: All you need to know

The menstrual cycle is a natural cycle experienced by most biological females. It starts during puberty, and continues on to the menopause at around 50 years old.

Understanding the menstrual cycle is important for people going through it, and can also be valuable knowledge for any romantic partners.

What is the menstrual cycle?

The menstrual cycle is a biological process, taking place in biological females of reproductive age. Essentially, it's your body's process of preparing for a baby and then clearing itself out if those preparations aren't needed.

Usually, the menstrual cycle lasts for approximately 28 days. Some people will have shorter cycles, some will have longer cycles, and others may have unpredictable cycles that vary from month to month.

The menstrual cycle is controlled by hormones. Every cycle, the uterus lining thickens in preparation for pregnancy. An egg is released during ovulation and makes its way to the uterus. If you don't become pregnant, the lining sheds and is removed through a menstrual period.

What are the menstrual cycle phases?

There are four phases to the menstrual cycle. Typically, the cycle is measured from the first day of your period, or menstruation:


During this part of the process, the lining of the uterus (also known as the endometrium) is shed. It leaves the body through the vagina, in a fluid that comprises of endometrial cells, mucus, blood and water.

For most people, this phase lasts between 3 and 7 days.

Follicular phase

This phase starts alongside menstruation and ends at the point of ovulation. Hormones cause the ovary to produce between 5 and 20 follicles. Each of these follicles will house an egg, and usually just one will mature. The same hormones cause the lining of the uterus to start to thicken once again.


Usually happening halfway through the cycle, around day 14, ovulation is the process of an egg being released by the ovary. This egg will travel along the fallopian tube, making its way to the uterus. If it doesn't make contact with sperm within approximately 24 hours, the egg will die.

Luteal phase

The follicles on the ovary, during the final two weeks of the cycle, will transform into corpus luteum. This produces hormones that will keep the lining in place in the uterus, until the body can fully register any potential pregnancy.

If an egg has been fertilised, it will implant in the lining of the uterus. At this point, it produces its own hormones to maintain the corpus luteum. That way, the lining will remain in the uterus throughout the pregnancy. If an egg is not fertilised, the corpus luteum withers at around day 22. Once the corpus luteum has died and stopped producing hormones, the lining of the uterus sheds.

Periods can affect women in many different ways, some women may suffer from very heavy periods and period pains while other may not be affected by their period.

What happens during ovulation?

The ovulation process occurs approximately 24 hours after a surge in luteinizing hormone (LH).

Ovulation is the release of an egg from an ovary, where it has matured over the previous two weeks.

The whole process is carefully controlled by the body's hormones. It is the luteinizing hormone that triggers the release of the egg.

Immediately following ovulation, the egg will begin its journey. It travels along the fallopian tube, making its way towards the uterus. It will stay alive for only 24 hours, and must be fertilised during this time to result in a pregnancy.

If you're trying for a baby, sperm must meet the egg within 24 hours of ovulation. Whilst the egg can survive for only 24 hours, sperm can survive a bit longer. Some will last up to five days within the uterus and fallopian tubes, which means that you could get pregnant from intercourse within a window of up to six days.

The ovulation phase will be delayed or stopped if you have taken the morning after pill such as ellaOne. This is to prevent the release of the egg and stop pregnancy. 

How can I track my menstrual cycle?

There are many reasons that you might want to track your menstrual cycle. If you're trying to conceive, you can track your cycle to find your most fertile signs. You may also want to track your cycle in order to monitor your health, manage weight loss expectations, or simply so that your period never takes you by surprise.

Using a mobile phone app

You can track your menstrual cycle using a mobile phone app. Menstrual cycle apps allow you to mark on a calendar the first day of your menstrual period. Over multiple months, you will be able to calculate how long each cycle lasts. This is the amount of time from the start of one period to the start of the next.

These apps will calculate, using your cycle, your likely day of ovulation. They can also be used to work out what's described as your 'fertile window' - the days to have intercourse, if you are trying for a baby.


Using a thermometer can help you to track your menstrual cycle. Your temperature should increase very slightly (up to 1.0°C) during the luteinizing hormone surge. You won't notice this without a thermometer, but may discover a pattern if you check your temperature daily.

Pen and paper

If you don't want the fancy functionality of a period tracking app, then you can do the same with any diary or calendar. Simply mark the first day of your period on your calendar or diary each month, to quickly build up a clear understanding of how long your menstrual cycle lasts.

It's important to note that all forms of tracking are slightly inaccurate. Even a tracking app, with its functions and calculations, won't get all the details right. The human body is unpredictable, and it's important not to rely on menstrual cycle tracking as a form of birth control of contraception.

Even outside your assumed fertile window, pregnancies can still occur. Your body may release an extra egg one month, or you might have an unusual cycle with ovulation happening earlier or later than normal.

Tracking your cycle can help you to increase your chance of pregnancy, and to quickly identify any unusual months that might be signs of a health concern, but cannot be relied upon as an alternative to proper contraception.

By tracking your menstrual cycle you can also identify if your period is due to come at an inconvenient time. If that is the case there are a number of medicines to stop your period for a certain amount of time. For example women may choose to delay their periods if they are going on holiday or getting married.

When does the menstrual cycle stop?

The term menopause is the medical diagnoses used to describe the years when a woman’s ovaries gradually start to produce less eggs and fewer female hormones such as oestrogen and prohesterone.  

The reduction in these hormones will mean that periods will become less regular and will gradually stop altogether. This process can produce many symptoms and conditions in women which is why it is common for women to be prescribed hormone replacement therapy medications which involves replacing the hormones that were previously produced by the ovaries in order to reduce symptoms related to a natural drop in these hormones.

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