All you need to know about pregnancy testing

Asian woman looking at pregnancy test
  • Is the pregnancy test positive or negative?
  • When to do the test?
  • What to do next?

Wondering if you might be pregnant can be a difficult time. You may be either desperate to be pregnant, or desperate not to be pregnant – but either way, you want to know as soon as possible – and be sure of the result.

Read on and see what pregnancy testing is all about, how and when to test, and what the results may mean.

What is a pregnancy test?

When a sperm fertilises an egg, and a pregnancy is first formed, this developing ball of cells starts to produce a hormone called Human Chorionic Gonadotrophin – or known as beta hCG. This can be detected in your urine.

At the very beginning of a pregnancy, the levels of this hormone are so low they cannot be detected by modern pregnancy testing kits.

After around 14 days, most modern pregnancy testing kits can now detect the level of beta hCG. If the pregnancy test is positive, beta hCG has been detected.

If you test too early, your pregnancy test may be negative, even though you are actually pregnant.

A pregnancy test is likely to be positive 14 days after conception, and this means around the first day of a missed period.

However, most doctors will advise you to do the test at least 7 days after you have missed your period. By waiting a little longer to do the test, this means the result is very likely to be accurate.

Sometimes girls will visit a clinic, saying they had sex the night before and worried they could be pregnant, and ask for a pregnancy test today. A pregnancy test the day after unprotected sex will not test positive yet from this encounter. You need to wait at least 14 days, as stated above.

However, if you have had unprotected sex, and do not want to be pregnant, this is an excellent opportunity for you to take emergency contraceptionthe ‘morning after pill’.

This is safe, and very effective, but there are rules for taking it and you must seek help and advice without delay.

Pregnancy tests explained

Pregnancy test strip

Beta hCG produced by the developing pregnancy, is excreted from your body in your urine. This is why a urine sample is needed for a pregnancy test.

An early morning urine sample is recommended for the test. This is because the urine is most concentrated in the morning, when you have been asleep overnight. The pregnancy test will be more likely to test positive if there is a higher concentration of beta hCG.

Whichever pregnancy test you use, the principle is the same. The kit contains an antibody – a protein produced by the immune system, which is specific to beta hCG. If beta hCG is present in your urine, the antibody will stick to it, and is attached to a colour dye. A coloured line or a coloured dot then appears on your test window. If these are present, the pregnancy test is positive. If you want to know more about this, see How do pregnancy tests work?

How accurate is a pregnancy test?

Most modern pregnancy testing kits are said to be 99% accurate, so long as you follow the manufacturers’ instructions.

Top tips for best results from a pregnancy test

  1. Do not test too early – wait a minimum of 14 days from the possible date of conception. For most women this will be the first day of a missed period. (If you have irregular periods, go by your longest cycle.)
  2. When you purchase the test, make sure you have checked the expiry date, and read the instructions. Use only UK/EU approved tests.
  3. Use the test on a urine sample you have passed first thing in the morning. This will be a concentrated sample, and it is most likely to give an accurate result.
  4. Sometimes you need to pee on a stick, or dip a wand into the urine for a number of seconds. Make sure you saturate the stick with urine, or leave the stick in the urine for the correct length of time.
  5. Check that the control window shows that the test has worked. If the control window does not change colour, you need to repeat the test, with a new pregnancy test, preferably the following morning, with a fresh early morning urine sample.
  6. Wait the required time to read the result usually around 3 minutes.
  7. If the test is negative and you are still concerned you could be pregnant, repeat the test in 7 days time.
  8. If you have symptoms such as low abdominal pelvic pain, dizziness, feeling faint, and/or unusual/heavy bleeding – seek urgent medical help.

What is the meaning of a negative pregnancy test?

More than likely, this means you are not pregnant.

However a test can be falsely negative because:

  • You tested too early.
  • The test is out of date.
  • Your urine is too dilute – an early morning sample is preferable.

Some medication can cause this:

  • Diuretics
  • Promethazine
  • Anticonvulsants
  • Parkinsons’ drugs
  • Hypnotics
  • Tranquilizers

What is the meaning of a positive pregnancy test?

In most cases, it means you are not pregnant. However very occasionally, a pregnancy test can be falsely positive:

  • You have recently had a pregnancy.
  • Miscarriage – pregnancy loss – it can take 2 weeks or longer after a pregnancy fails for a pregnancy test to become negative.
  • An Ectopic pregnancy.
  • A molar pregnancy.
  • Menopause.
  • Fertility drugs e.g. Pregnyl, Humegon or Pregonal (but not Clomid).

What if a positive pregnancy test becomes negative one week later?

This may mean you have had a miscarriage. Many pregnancies do not continue to develop and hence the production of beta hCG stops.

Alternatively, abnormal pregnancies such as miscarriages and ectopic pregnancies can produce fluctuating results. If this happens, you must discuss this with your doctor.

In all cases, if you feel unwell, or have lower abdominal/pelvic pain or heavy bleeding, you should seek help without delay. Rarely, ectopic pregnancies may cause abnormal pregnancy test results and this is an emergency situation.

Always inform your doctor/midwife if you are pregnant and have any vaginal bleeding. It may be due to something simple but you do need to be assessed.

How else can a pregnancy be detected?

  • A blood test to measure the levels of beta HCG in your blood stream. This is a more accurate way of documenting a pregnancy, and is usually done in women who may have an ectopic pregnancy. It is used to monitor an emergency situation, to see if hormone levels are rising or falling.
  • An ultrasound scan. This can only detect a pregnancy from about 5–6 weeks. In very early pregnancy there is almost nothing to see. This is why in general you would not be scanned too early in pregnancy. Your routine scan in a healthy pregnancy is at around 12 weeks.
  • A pelvic examination. A pregnancy is just one cause of an enlarged womb (uterus).

Is it safe to do pregnancy testing at home?

Yes it is – when you purchase a pregnancy test in the pharmacy, these will generally be very similar testing kits to the tests used by your GP or practice nurse, or in a clinic.

What to do if I think I might be pregnant, but I’m not having periods, so I can’t time when to do the test?

You can do a pregnancy test at any time. However, bear in mind the fact that it does take around 14 days from the day of conception for a pregnancy test to be positive.

So if you had unprotected sex for the first time, say 1 week ago, it will still be too early today, for a pregnancy test to give you an accurate answer. You need to wait another 7 days.

If the pregnancy test is then negative, repeat it in another 7 days time, to be 100% sure.

If something has happened, and you think you are at risk of an unplanned pregnancy remember two things:

  1. Consider your options for emergency contraception. This is safe, an effective but needs to be taken early. You visit your GP surgery or a Sexual Health Clinic as soon as possible. It is also possible to obtain emergency contraception to keep ready for when needed from Dr Fox. It is NOT advised to order emergency contraception online for immediate use as there will be a delay in receiving due to delivery.
  1. Continue and don’t stop your contraception. The contraceptive pill, for example, has not been shown to be associated with abnormal pregnancies, and if you stop taking it, and you are not pregnant now, you then run the risk becoming pregnant at any stage! So if you don’t want to be pregnant, always continue your contraception and don’t stop!

Can anything interfere with the pregnancy test result?

The test can be a false negative test or a false positive test (see above). Of note: commonly used medicines like hormonal contraception – or drugs and alcohol – do not interfere with a pregnancy test result.

Can you have a positive pregnancy test during your period?

Some women report their pregnancy test was positive when they were having a period. However in truth, bleeding in early pregnancy is quite common. The bleeding is not actually due to a period. The bleeding is more likely due to implantation of the fertilised embryo in the lining of the womb (uterus), or could be from the cervix for example from cervical erosion or a cervical polyp. Sometimes bleeding in early pregnancy signifies an abnormal pregnancy such as a miscarriage or an ectopic pregnancy

Very rarely, bleeding may actually be due to disease of the cervix, such as cervical cancer.

It remains extremely important that you attend for your cervical smear tests regularly.

 Cervical smears save lives! Don’t miss out on yours!

When does a pregnancy test become negative after a miscarriage or an abortion?

A pregnancy test may still be positive up to 2 weeks, and rarely longer, after a complete miscarriage.

What should I do if my test is positive and I plan to go ahead with the pregnancy?

If you plan to go ahead with the pregnancy, you must contact your GP/midwife to book antenatal care.

You can work out your delivery date using a due date calculator.

It’s vitally important you keep healthy when you are pregnant, for the growth and development of your baby.

It’s very important to eat well, to try not to smoke, not to take drugs, and not to drink alcohol. Your midwife will discuss this further with you.

What should I do if my test is positive, but I have no idea what I want to do?

It’s very understandable that you may be shocked, confused and uncertain what to do next.

It takes time for the realisation that you are pregnant to sink in, and for you to come to terms with your feelings.

You need to be able to talk this all over with your partner, friends and family, and sometimes with a doctor/nurse or a counsellor, to consider your options.

Some organisations such as The Family Planning Association (FPA), BPAS, Marie Stopes UK and Brook offer free unplanned pregnancy counselling.

A pregnancy is not the end of the world! There is help and support out there from trained people who will not judge you, and will be sympathetic and supportive.

If you feel certain you do not want to go ahead with the pregnancy, you can request to terminate the pregnancy. You need to act without delay.

For more information read the FPA advice.

Other key points

Don’t forget to get tested for STI’s. Most of these have no symptoms at all! Yet some can cause miscarriage, and ectopic pregnancy.

If you want to be pregnant, or perhaps have just had a miscarriage or an ectopic, this is a very good reason to make an appointment either at the Sexual Health Clinic or at your GP, and have a full STI screen.

Alternatively, you can obtain a home STI testing kit online.

Do something amazing for yourself today!

Which is the best pregnancy test?

It’s difficult to say any test is truly ‘best’ – however in a 2011 published medical study of six currently available tests, First Response tests, both manual and digital, which detect beta hCG at the lowest level (5.5 mIU/ml), detected 97% of 120 pregnancies on the first day of the missed period. The First Response Test performed the best of all six tests studied. (This does dispute the manufacturers claim that it detects 99% of pregnancies on the first day of the missed period however.)

What’s the difference between a manual, or a digital pregnancy test?

Pregnancy tests can be purchased as manual or digital.

Manual tests rely on chromatography – biochemical colour changes – and do not contain a battery.

Digital tests contain a battery. Check the expiry date – this will also ensure the battery is in date. Do not use these tests near other sources of electromagnetic radiation – keep away from mobile phones. The battery should be disposed of according to your local regulations. Do not dispose of them in fire, or attempt to recharge the batteries.

Final thoughts

No tests are ever 100% reliable! It’s important to understand what is being tested, and why and how the test could be giving the wrong result.

Modern pregnancy tests are very accurate – and if used correctly will detect a pregnancy reliably from the first day of a missed period in at least 97% of cases. However, do follow the advice here, and make sure if you have any doubts about the results, you repeat the test, and consider seeking medical advice.

For more information

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