You won't be aware of it yet, but you've just become pregnant – congratulations!
Once the egg is fertilised, it travels along the fallopian tube and embeds itself in the wall of the womb (uterus).
It starts to produce a hormone called ‘human chorionic gonadotrophin,’ which stops you having a period and shows in your urine - this is what home pregnancy testing kits can detect when you miss your first period.
The first trimester
The first three months of pregnancy is a very important time in your baby’s development, as this is when the main structures of the body and organs begin to form. Be extra-careful about taking any drugs or medications - read the packaging very carefully and check with your doctor or pharmacist before you take anything.
It’s best to avoid alcohol, too, in the first trimester (though if you had a glass of wine before you realised you were pregnant, there's no need to panic!). Check the current guidelines on alcohol during pregnancy.
Think about eating healthily
Many mums-to-be decide to eat and drink extra-healthily during pregnancy. Choosing organic foods can help you plan a healthy diet without worrying about pesticide residues or artificial additives. Visit www.eatwell.gov.uk for more information on eating healthily during pregnancy.
There are also a few foods that are best avoided during pregnancy. We've made a handy downloadable list of them to help you out.
Are you taking any medication?
It is important that you check any medications you are taking with your doctor, to make sure they are safe to take during pregnancy.