Many women don't suspect they're pregnant until they've missed a period, but there may be other indications:
Sickness and/or feelings of nausea
A strange, 'metallic' taste in your mouth
Breast tenderness, tingling and enlargement
The small bumps - 'Montgomery's tubercules' - on your nipples becoming more obvious
Stomach pains
Tiredness
Constipation
Needing to urinate more often
Going off certain things, such as coffee and fatty foods
Increased vaginal discharge
Some women experience very light bleeding (called 'spotting') that they mistake for their period.
Home pregnancy tests can be on the first day of your missed period, and some very sensitive tests can be used sooner than this.
The tests work by detecting the hormone human chorionic gonadotrophin (hCG) in your urine. A chemical in the plastic stick changes colour when it comes into contact with this hormone, so the usual way of testing is to urinate on the end of the stick and watch for the result in the window.
Pregnancy tests are very accurate as long as you use them properly. It's possible to have a false negative, when the test says you aren't pregnant but you are. If your period still doesn't arrive, repeat the test or check with your GP.
You can buy home pregnancy tests online, in the supermarket or at your local chemist. Some GPs, family planning clinics and young people's services (such as Brook Centres) offer free tests, as do some pharmacies, the British Pregnancy Advisory Service and Marie Stopes International clinics.
The length of your pregnancy is dated from the first day of your last period, even though you actually conceive two weeks or so after this date (depending on the length of your cycle). Your baby is likely to be born two weeks either side of the due date.
Check your due date and what's happening within your body week by week with our Pregnancy calendar. All you need to know is the first day of your last period.
Most women see their GP to arrange antenatal care, but you can book directly with a community midwife if you prefer.
If you've had a positive home test, you just need to tell your doctor. They're unlikely to test you again. You may be offered a 'dating' scan, even if you're sure of your dates. This is an ultrasound scan done in early pregnancy to find out the size of your uterus and the embryo, to help determine how pregnant you are.