The menstrual cycle is a fundamental part of life for all women but it is a topic which often goes undiscussed.

Many may have questions relating to the links between conception and the menstrual cycle, but be hesitant to ask their regular GP.

Why are periods sometimes inconsistent? What can affect them? Is there are a time of the month where it is harder or easier to get pregnant?

To help those who may be unsure, below we have supplied a helpful calendar guide to the monthly menstruation cycle, along with some answers to a number of regularly asked questions relating to menstruation and conception.

Menstruation calendar

  1. Day 1

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Signified by the first day of your period when you experience a ‘bleed’.

This is triggered by a drop in the progesterone hormone when the body recognises that fertilisation of the egg has not occurred. The endometrium must be renewed in preparation for a new egg.

  1. Days 3-7

Bleeding usually stops around this point. A number of eggs in the ovaries begin to mature ready for release at the point of ovulation.

  1. Days 7-14

One egg will continue to develop and reach maturity. The lining of the womb will start to thicken in preparation for ovulation.

  1. Day 14

Around this time, a change in female hormones will cause the mature egg to be propelled out of the ovary to commence its journey.

This is known as ovulation.

Over the next few days the egg will travel down the fallopian tubes eventually meeting the womb.

If you have unprotected sex at this stage a sperm may come into contact and thus fertilise your egg. The combined cells will travel into the womb where they will attach themselves to the thickened endometrium and begin to develop.

  1. Day 25

If the egg has not been fertilised hormone levels will drop and the egg will be broken down. The new period will begin in the next few days.

What is the menstrual cycle?

The menstrual cycle is the term given to the monthly process followed by the female reproductive system.

It covers ovulation, fertility and periods. The length of the cycle is measured from the first day of the period to the day before the next period. For many women this is about 28 days but can vary.

Periods tend to start when someone reaches puberty, typically around the age of twelve, although they can start earlier or later. The ovaries start to produce female hormones around this time which trigger the different episodes in the cycle.

What is ovulation?

Ovulation refers to the release of a developed egg from the ovaries. For women who follow a regular 28 day cycle this is usually around day 14.

Levels of the oestrogen hormone rise initiating the ovulation process, whilst progesterone thickens the lining of the womb.

During each menstrual cycle a mature egg is released from the ovaries. This is usually just one single egg but occasionally two might develop and be released at the same time. The egg lives for approximately 24 hours during which time it passes into the fallopian tube.

If fertilisation by a sperm cell does not take place, the egg will be broken down in the womb and absorbed by the body.

What are periods?

If pregnancy does not occur at the time of ovulation, the thickened womb lining, also known as the endometrium, must be shed in preparation for the following month’s lining.

The endometrium is a mucous membrane made up of cell tissue, which is broken down and passed out along with blood via the cervix and through the vagina. This is known as a period and can cause discomfort and pain while the womb actively breaks down the lining.

Women will experience this to varying extents during their periods, and the flow may be heavy or light and can continue for between three and seven days.

The period flow is usually captured by specially made female sanitary products that come in a range of sizes and styles to suit individual preference. The most commonly used products include tampons, pads and menstrual cups, all of which absorb or capture the menstrual fluid so that it can be disposed of conveniently and hygienically.

What is premenstrual syndrome (PMS)?

Throughout the menstrual cycle, levels of hormones change in the female body; and these fluctuations can sometimes manifest physically in a variety of ways.

In the two weeks prior to the start of a period some women develop symptoms of PMS or premenstrual tension (PMT). These can include but are not solely limited to breast pain, mood swings, being easily irritated, a loss of interest in sex and stomach bloating.

Severe symptoms that prevent the woman from getting on with their daily life may be diagnosed as premenstrual dysphoric disorder (PMDD) which is thought to affect between 2 and 10 percent of menstruating women.

At what stage are you most fertile?

You are most likely to get pregnant around the time of ovulation. Some women notice changes in their body around this time such as breast tenderness, or changes in vaginal discharge and body temperature.

Sperm can live in the fallopian tubes for up to seven days, so it is important to use contraception throughout your cycle if you do not wish to become pregnant.

How long will a person have periods for?

The average ages for starting periods and starting menopause are 12 years and 52 years respectively.

This means that most women will experience periods for around 40 years of their life resulting in close to 480 periods in a lifetime, although this number can obviously vary depending on pregnancies, illnesses and contraception.

Does a ‘normal’ menstrual cycle exist?

Unfortunately not. Every woman is different and so each cycle can vary in length and flow. The average length of a menstrual cycle is 28 days but this does absolutely not mean that women whose cycles are longer or shorter are ‘abnormal’.

The majority of women will lose between 30-40 millilitres of blood during a menstrual bleed but these numbers can increase. Consistent periods where over 60 millilitres of blood is lost may be diagnosed as menorrhagia or heavy periods. There are treatments available to help ease the symptoms of menorrhagia. 

What can affect a regular menstruation cycle?

Most women will get to know their own menstrual cycle but there are things that might change or alter it in some way.

The regularity of periods can be affected by stress, sudden changes in weight, diet, medication, health conditions such as polycystic ovary syndrome (PCOS) and of course pregnancy. Your period may be lighter or heavier, occur less frequently or disappear entirely, known clinically as amenorrhoea.

If you have concerns about changes in your menstrual cycle you should speak to your doctor.

Can you have sex during your period?

Yes, however there may be an increased risk of contracting or transmitting sexually transmitted infections (STIs) at this time, so practising safe sex (with a barrier contraceptive) is important. Sex during the menstrual bleed can also be uncomfortable because the cervix may be in a different position to what it is usually.

Page last reviewed:  01/10/2020