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Scroll down to watch a video about pregnancy myths and how to do a pregnancy test
But when should you take a pregnancy test? And what do the results mean?
When to do a pregnancy test
If you're pregnant, the amount of HCG in your body rises rapidly in the early days and weeks, and a home pregnancy test can detect this in your urine.
You may suspect that you're pregnant because you have certain symptoms, such as enlarged or tingling breasts, nausea (feeling sick), dizziness, a metallic taste in your mouth, or a feeling that your period is about to start. However, not all women have these symptoms.
Most home pregnancy tests can be carried out on or after the day your next period is due. (Counting the number of days from the first day of your last period until the day before your next period is due to start will give you your usual cycle length.)
If you don't know when your next period is due, wait at least 19 days after you last had unprotected sex before you do the test.
If your cycles are irregular, allow for your longest recent cycle length before testing.
Negative test results
If you get a negative (not pregnant) result from the pregnancy test, but still think you could be pregnant, wait another three days then do a test again. You may have conceived (got pregnant) later than you thought, so there wouldn't have been enough HCG in your urine to be picked up by the first test.
Speak to your GP if you still get a negative result after a second test but your period has not arrived.
You can also ask your GP, or midwife, to do a blood or urine test to show whether or not you're pregnant. Most surgeries will accept your positive home pregnancy test as confirmation because the tests are now as accurate as the ones used by health professionals.
Testing after miscarriage, abortion or ectopic pregnancy
If you've had a miscarriage, an abortion or an ectopic pregnancy, it is possible that a home pregnancy test may test positive for some time afterwards. This is because there may still be raised levels of HCG in your body.
In this situation, if you get a positive test result, it does not necessarily mean you are still pregnant. However, you may need to see your GP depending on how long ago your pregnancy ended.
If you've had a miscarriage, you may still get a positive result up to 35 days afterwards. See your GP if you are still testing positive after 35 days.
If you've had an abortion, a pregnancy test result may stay positive for a few weeks afterwards. See your GP if the test still gives a positive result after four weeks.
If you've had an ectopic pregnancy, a pregnancy test can return a positive result for up to one month after the embryo was removed. See your GP as soon as possible if you still have a positive result after one month.
Having a pregnancy test if you're on the Pill
It is always advisable to take a pregnancy test if you think you might be pregnant, regardless of the type of contraception you currently use, or have used in the past.
Hormonal methods of contraception, such as the contraceptive pill, and contraceptive implants and injections, contain the hormones oestrogen and progesterone, and they work by changing a woman's hormone balance. However, these hormones will not affect the result of a pregnancy test because they are not used to measure whether or not you are pregnant.
If you're pregnant, the amount of HCG in your body rises rapidly in the early days and weeks, and a home pregnancy test can detect this in your urine
How pregnancy tests work
A pregnancy test only reacts to the pregnancy hormone human chorionic gonadotropin (HCG). However, if you are pregnant, this hormone will not be present in your urine or blood until 13-16 days after ovulation, which is around the time that you would normally get your period. Until this time has passed it will not be possible to see a positive result in a pregnancy test.
Urine tests require a certain level of HCG to be present in order to show a positive pregnancy result. Blood tests are more sensitive because they can detect a smaller amount of HCG, which means that pregnancies can be picked up earlier, usually six to eight days after ovulation.
You can have a blood test at your GP surgery but it is recommended that, before booking an appointment, you first take a home urine test.
HCG is sometimes used in fertility treatment, which could cause a false-positive result (where the result is positive but you are not actually pregnant). You should therefore wait 14 days between fertility treatment and taking a pregnancy test.
A negative result
If you get a negative result after taking your pregnancy test, it can mean several different things. It can mean that you're not pregnant. Or it can mean you have taken the test too early.
Taking a test early is easily done because it can be difficult to work out the exact day that you began ovulating. If you think you may have taken the test too early, wait a few days then take a second test or, alternatively, see your GP for advice and possibly a blood test.
A negative result may also be because you've timed the test wrongly. For instance, if you collect a sample of your urine for testing and don't do the test within 15 minutes, it may affect the result. Home pregnancy tests can vary, so always carefully read the instructions before you do the test.
Drinking too much fluid before a test can also dilute your urine, which can affect the level of HCG in your sample.
If you're in any doubt about your pregnancy test result, make an appointment with your GP.
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