Pregnancy happens after unprotected sex or a problem with a method of contraception.
Getting facts on fertility can help for couples 'trying' for a baby.
A woman's monthly cycle involves hormonal changes telling the ovaries to release an egg.
The egg travels down the fallopian tubes from the ovaries to the womb (uterus). The womb lining becomes thicker in readiness for an egg being fertilised in the fallopian tube. If there's no fertilisation that month, the womb lining and some blood is removed though the period. The monthly cycle lasts around 28 days. The first sign of a pregnancy is usually a missed period.
An egg may be fertilised by sperm within 12 to 24 hours of being released. Because sperm itself can survive for up to 7 days inside a woman, fertilisation can happen even if a couple had sex before the egg was released.
Genes from the dad are in the one sperm that fertilises the egg. Genes from the mum are in the egg, which once fertilised is known as a zygote.
The zygote reaches the uterus around three to seven days after fertilisation. Once implanted to the wall of the uterus, it starts growing.
The next milestone for the zygote comes eight weeks after the conception, when it becomes known as a foetus.
If a woman thinks she may be pregnant, a pregnancy test of her urine done several days after a missed period (and sometimes even before she misses a period) can confirm it. Test kits can be bought from pharmacies or can be obtained through GP surgeries, sexual health clinics, and family planning clinics.
There are steps to take before planning a pregnancy, including taking folic acid and vitamin D supplements, and talking to your GP about any lifestyle changes – such as achieving a healthy weight and quitting smoking.
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