Getting pregnant - how do I know when I am fertile?

June 29

  • Preconception

Getting pregnant - how do I know when I am fertile?

Nowadays it is quite difficult for women to properly know their own menstrual cycle and the changes which it prompts in their body. This may be bec...

By Malena Monteverde, Registered Midwife

Nowadays it is quite difficult for women to properly know their own menstrual cycle and the changes which it prompts in their body. This may be because many women use hormonal contraception, which can mask useful signs that help us recognise the patterns within our cycles.

Once contraception has been stopped, your fertility usually returns to normal quite quickly. In fact, between 80-90% of women under the age of 40 will become pregnant within the first year of trying to conceive, if they are having sex regularly- every 2-3 days. Of the remaining 10-20%, half will become pregnant during the 2nd year of trying to conceive, whilst the other half will take longer or will need some help to conceive.

Your body gives you several clues during your menstrual cycle as to when the most and least fertile times are, so it is good to learn a little bit more about what to look out for.

Your menstrual cycle

The average woman’s menstrual cycle lasts for 28 days, although some women will have shorter or longer ones, as we are all individuals. The most likely time an egg will be released during this time is approximately 14 days after the first day of your last period. This means that you will be most likely to conceive when you have regular sex around the midpoint of your cycle.

During this time the main hormones involved are oestrogen and progesterone. These play their part in ripening egg follicles - of which usually only one will be released - and in thickening the lining of the womb, ready for a fertilised embryo to implant into. They also control the shedding of this lining if an embryo doesn’t implant, changing the cervical mucous produced during the cycle.

Know your body

Every woman will have a discharge from their vagina during their menstrual cycle. The discharge you observe once you are not using hormonal contraception can give you a clearer idea of what is happening in your body.  Knowing the different types of discharge can help you to gauge more accurately when you are likely to be most fertile and when conception is less likely.

Vaginal discharge is mainly produced by the cervix. The cervix is the entrance to the uterus and goes through many changes throughout your menstrual cycle. It changes position, consistency and shape as well as producing secretions which affect how any sperm present can move into the uterus.

You may notice that, following menstruation, your discharge becomes minimal and you have a few ‘dry days’. The chance of conception during these days is very low. As the follicle matures in one of your ovaries, this discharge slowly increases and becomes a little sticky, varying in colour from white, cloudy or pale yellow. Vaginal discharge continues to increase as you approach ovulation, becoming more watery and elastic. Ovulation happens when your egg is released from the ovary and into the fallopian tube, where it could be fertilized by a sperm.

On ovulation day and the days immediately approaching it, your vaginal discharge will significantly increase in amount - usually becoming copious - and become clear, stretchy and slippery, resembling an egg white. This is the perfect medium for sperm to survive and be transported through your reproductive system to meet your egg. These are your most fertile days.

Some women experience a dull ache on one side of their lower abdomen just before, during or just after ovulation. This is known as mittleschmerz, meaning ‘middle pain’ in German. Although the cause of this is uncertain, the possible irritation of nearby nerves by the fluid that is released with the egg is thought to play a part in it.

An egg that has not been fertilized can survive in your body for 12-24 hours and sperm may survive for up to 5 days, meaning that most women are potentially fertile for approximately 6-7 days in every cycle.

If an egg is not fertilized, the levels of oestrogen that surged before ovulation will rapidly decline and progesterone will take over. Your discharge will suddenly decrease and become sticky and cloudy again. These are considered non-fertile days. The change in hormone levels will cause a change in the lining of your womb and lead to menstruation, around day 28 of your cycle.


If you are trying to conceive, observing your body’s changes and your vaginal discharge throughout your cycle could provide valuable information as to when you might be most fertile. Having regular intercourse during this time will increase your chances of falling pregnant. For more information on trying to conceive, visit our Trying to Conceive Hub.