Pregnancy Guide
NHS Choices

Checks for Abnormalities

You will be offered some screening tests during pregnancy to try to find any health problems that could affect you or your baby, such as infectious diseases, sickle cell and thalassaemia, Down’s syndrome, Edwards’ syndrome and Patau’s syndrome, or physical abnormalities.

The tests can help you make choices about care or treatment during your pregnancy or after your baby is born.  All screening tests offered by the NHS are free.

What are screening tests?

Screening tests are used to find people at higher chance of a health problem. This means they can get earlier, potentially more effective, treatment or make informed decisions about their health.

Screening tests are not perfect.  Some people will be told that they or their baby may have a higher chance of having a health problem when in fact they do not have a problem.  Also, a few people will be told that they or their baby have a low chance of having a health problem when in fact they do have a problem.

What are the risks of screening tests?

Screening tests will not harm you or your baby, but there are some risks to consider.  Some screening tests in pregnancy can lead to serious decisions for you.  For example, screening tests for Down’s syndrome, Edwards’ syndrome and Patau’s syndrome can lead to difficult decisions about whether to have an invasive test that carries a possible risk of miscarriage.

If the results of invasive tests are positive, they can lead to a decision about whether you want to continue or end the pregnancy.  Having a further test or termination will always be your decision, and health professionals will support you whatever you decide.

You may want to think carefully about whether or not you want to have these screening tests.

When will I be offered screening?

Different screening tests are offered at different times during pregnancy.

The screening test for sickle cell and thalassaemia, blood group and antibodies, infectious diseases should be offered before 13 weeks, but can be offered later.

You will be offered screening for Down’s syndrome, Edwards’ syndrome and Patau’s syndrome around the time of your early pregnancy dating scan, should be offered before 13 weeks, but can be offered later.

You will be offered screening for abnormalities at a mid-pregnancy scan (fetal anomaly scan) when you are around 18-21 weeks pregnant.

Will screening tests give me a definitive answer?

No - a screening test does not usually say for certain if you or your baby have a health problem.  It tells you if you or your baby have a higher or lower chance of having a problem.

Women or babies found to have a higher chance of a problem will often be offered an invasive test.  An invasive test gives a more definite "yes" or "no" answer.

Do I have to have the screening tests?

No - it's up to you whether or not to have a screening test.  It is a personal choice that only you can make.  You can discuss each of the screening tests you are offered with your midwife or doctor and decide whether or not it is right for you.

Some of the screening tests you will be offered are recommended by the NHS, such as:

  • blood tests for infectious diseases
  • eye screening if you have pre-existing diabetes (not gestational diabetes)
  • newborn checks

This is because the results from these tests can help make sure that you or your baby get urgent treatment for serious problems.


By law, everyone working in, or on behalf of, the NHS must respect your privacy and keep all information about you safe. The NHS Constitution sets out how the NHS should handle your records to protect your privacy. In addition, there are laws in place to ensure confidentiality is maintained.

Screening records are only shared with staff who need to see them. Sometimes information is used for audit research purposes to improve screening outcomes and services. Information about this will be provided when you are screened.


Last Updated: 08/11/2017 10:00:27