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Fertility facts

Contraception and conception: some facts about fertility 

When is a women most fertile?

Lots of people do not know when a woman is most fertile during her menstrual cycle — in other words, when she is most likely to become pregnant.

A woman will normally release an egg (ovulate) every month 12-16 days before the start of her next menstrual period. This is the most fertile time of her menstrual cycle.

Does ovulation happen at the same time every month?

The time that ovulation occurs within each cycle can vary. It can depend on length of the cycle and on a range of external factors over which a woman may have no control. Examples of external factors could be stress, travel or illness.

Where a woman has a regular, 28-day cycle, she will usually ovulate around the middle of her cycle. The egg she releases can survive for between 12 and 24 hours inside her. The sperm released by the man can survive for between 5 and 7 days inside a woman’s body.

If a couple have sexual intercourse during this fertile time, the egg may be fertilised by a single sperm out of the millions released by the man when they have sex.

Many women have irregular cycles, so it can be difficult to identify their likely fertile time in each cycle. Every woman’s menstrual cycle is unique to her.

Remember to use contraception 

If a woman has sex without using contraception, she may become pregnant – even at a time in her cycle when she thought she was safe.

Please note that this is general information about fertility which does not replace medical advice. If you need further information about fertility, talk to your GP or go to a Family Planning Clinic.