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Screening tests during pregnancy

During your pregnancy, you'll be offered some routine tests known as screening tests.

For example:

Screening tests are done to find out if you or your baby are at a low or high risk of having certain health problems.

If you get a ‘high risk' result, you will be referred for more detailed tests called diagnostic tests. A ‘low risk’ result does not mean no risk.

Many screening tests are offered to all pregnant women. Other tests are only offered to women who are at high risk of a particular health problem.

Screening tests are usually free. But some people choose to pay for non-invasive prenatal screening (NIPS). NIPS is not offered as part of free public maternity services.

Difference between screening tests and diagnostic tests

Screening tests are usually non-invasive. This means the tests are done on the outside of your body. There's no risk of them causing a miscarriage.

Screening tests include blood tests and ultrasound scans.

Diagnostic tests may be more invasive or more expensive than screening tests. They usually tell whether you or your baby has a health problem more precisely. But they can sometimes increase your risk of miscarriage.

You will normally only be offered them if you:

  • are more at risk of a health problem
  • have had a positive screening test

Diagnostic tests include amniocentesis and CVS (chronic villus sampling).

Deciding to have pregnancy screening tests

Screening tests can help you make informed choices about:

  • continuing a pregnancy
  • care you may need during your pregnancy and the birth
  • care you or your baby may need after your baby is born

They can reduce the risk of you becoming seriously ill during your pregnancy.

Choosing whether to have screening tests done is an important choice for you and your baby's health. Only you can make the decision that is right for you, your pregnancy and your baby. Your birth partner or support person will help you make your choice.

Make an informed choice

It is important that you have all the information you need to make the right choice for you. Your midwife, obstetrician or GP are there to answer your questions. Ask them about your screening test options. Discuss these with your partner or family and friends.

Examples of questions to ask include:

  • Do I need this test?
  • What is this test for?
  • What does it mean if the test shows a 'high risk' result?
  • What should I do if I get a ‘high risk’ result?
  • What could happen if I do not have the test done?

Types of screening tests

There are different types of screening tests.

Blood tests

Most obstetricians, GPs and midwives would strongly recommend that you have blood tests.

Blood tests can give a snapshot of your current health. They can sometimes identify if you need any urgent treatment.

This could prevent:

  • you and your baby becoming very ill
  • your baby from having a disability or dying

These are usually done in the hospital or with your midwife at your booking visit.

Tests for sickle cell disease and thalassaemia

You might be offered extra blood tests to check for sickle cell disease and thalassaemia. These tests are usually offered before 10 weeks of pregnancy.

You're more likely to be offered this test if you or your family come from parts of the world where these conditions are more common, such as:

  • the Mediterranean
  • Africa
  • the Caribbean
  • India
  • Pakistan
  • other parts of Asia

Sickle cell disease and thalassaemia screening

Anomaly scans

You will be offered a mid-pregnancy ultrasound scan at around 18 to 22 weeks. It is sometimes called an anomaly scan or a fetal anatomy scan.

This scan checks for physical abnormalities in the baby.

If you have previously had a child with a cardiac disorder, you may be offered an ultrasound scan at 24 weeks. This will look specifically at your baby’s heart.

Fetal anatomy scans

Gestational diabetes screening

You might be offered screening for gestational diabetes. This is usually done in your maternity hospital.

In some maternity hospitals this test is offered to all women. In other hospitals, it is only offered to women who have other risk factors for gestational diabetes.

Non-invasive prenatal screening (NIPS)

Non-invasive prenatal screening (NIPS) is a common type of screening test for chromosomal conditions. It is sometimes called non-invasive prenatal testing (NIPT).

NIPS looks to see if your baby may have a high or low risk of:

  • trisomy 21 (Down syndrome)
  • trisomy 18 (Edwards’ syndrome)
  • trisomy 13 (Patau's syndrome)

You can choose to have the NIPS test. But you will have to pay for this. It is not offered as part of free public maternity services.

If it's not available in your hospital, you can get the tests done privately.

NIPS involves a blood test and an ultrasound scan. It is important that these are done together for best accuracy. This information forms an individual risk assessment.

NIPS is usually done after 9 to 10 weeks of pregnancy. It can also be done later in pregnancy.

The test looks at very small bits of DNA:

  • placental DNA
  • your baby’s DNA

DNA is a person's unique genetic code. These pieces of DNA will be in your bloodstream by about 10 weeks of pregnancy.

Almost all of the time these pieces of DNA are the same. But sometimes they are different. This is very rare.

In a small number of cases, the results of your NIPS test may not be clear. This may be because:

  • not enough cells were taken
  • there were technical issues

In this case, you will be offered a repeat NIPS test.

You'll be offered a diagnostic test to confirm your test result if:

  • the pieces of DNA are different
  • the result is positive
  • the result is high risk

Your obstetrician or midwife will discuss this with you. Talk to them for more advice and information about NIPS.

Diabetic retina screening

Diabetic retina screening checks for signs of diabetic retinopathy and other eye problems.

Diabetic retina screening in pregnancy

False results in pregnancy screening tests

Screening tests are not perfect. Sometimes false positive and false negative results can happen.

False positives

A positive result is a result showing you or your baby are at risk of having a health problem.

A false positive is when a test suggests you or your baby have a health problem, but further testing later shows you do not.

False positives can be very worrying. They can also mean you or your baby must have more tests.

False negatives

A negative result is when the test shows that you and your baby are not at risk of having a health problem.

Sometimes screening tests do not identify an actual health problem. This is called a false negative.

Page last reviewed: 22 December 2023
Next review due: 22 December 2026