Blood test screening in pregnancy

The purpose of blood tests in pregnancy was a common source of confusion for the women we spoke to. Blood tests are carried out for many reasons:

  • to check the mother’s blood group
  • to monitor the mother’s health, for example checking iron levels for anaemia, and look for conditions which may develop in pregnancy such as diabetes and pre-eclampsia
  • to screen her for conditions she may already have which can affect her or the baby (such as HIV or various sexually transmitted diseases)
  • to check whether the parents are carriers of inherited conditions such as sickle cell and beta thalassaemia (see our website on Screening for sickle cell and beta thalassaemia)
  • to screen for immunity to infectious conditions such as rubella which can harm the baby if the mother catches them while pregnant
  • to screen the baby for conditions such as Down’s syndrome.

Here we focus only on tests which screen for conditions in the baby, but many women we talked to weren’t sure why their blood was being taken (see Information for making decisions).

Having blood tests and other kinds of screening is treated as routine.

Age at interview 37

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Not everyone worried about this, and some happily trusted their doctor or midwife to act in their interests. One woman was concerned that her results were taking a long time to come back, including the tests to see if she was a carrier of sickle cell disease.

She had not had much information about blood tests, but trusted that staff were acting in her…

Age at interview 23

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She was still waiting for some blood test results to come back months later, including for sickle…

Age at interview 24

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Not everyone was aware they could have a blood test around the same time as their nuchal translucency scan, to produce a combined and more accurate assessment for chromosomal conditions, especially Down’s syndrome. The NHS Fetal Anomaly Screening Programme now recommends that women have the combined screening for Down’s syndrome (blood test as well as nuchal translucency scan) rather than just either test on its own. The vast majority of units in England, Scotland and soon Wales offer combined screening for Down’s syndrome.

One woman told how her first sample was damaged and the test had to be repeated.

She was well informed about the availability of the combined nuchal scan and blood test, but her…

Age at interview 37

Gender Female

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One person said she had missed the test because her fear of needles had led her to delay it. For another couple this blood test turned out to be crucial in detecting Turner’s syndrome, which the scan alone would not have picked up.

She had the combined blood test and nuchal scan in her first pregnancy. It was the blood test…

Age at interview 34

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The ‘quadruple test’ is a test for Down’s Syndrome and other conditions, that can be done between 14–20 weeks. It is offered to people who are unable to have the nuchal translucency scan.

She was informed about an extra blood screening test, but surprised the midwife would visit her if the results showed an increased chance that something was wrong.

Age at interview 32

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If you have had a result from a nuchal scan and blood test, it is not advisable to have the quadruple test as well, because it will also give you a result for Down’s syndrome and having two different assessments can be confusing.

After ending a pregnancy for a serious chromosomal condition (Edward’s syndrome), one couple decided against blood tests in their next pregnancy and relied only on scans. This was because the chance of their baby having a condition would automatically work out higher, because previous Edward’s syndrome is added as an extra risk factor. They did not want any further diagnostic tests. This time they felt better informed to make a real choice about screening.

They decided against blood tests in the current pregnancy and relied only on scans. This time…

Age at interview 35

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Another woman who had ended a pregnancy for spina bifida also relied only on scans in her next pregnancy. She felt she would have to wait anyway for the 20 week scan to know how severe the condition was, and the triple test might make her anxious unnecessarily.

She relied only on scans in her next pregnancy, and felt the extra blood tests might make her anxious unnecessarily.

Age at interview 26

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The non-invasive prenatal test (NIPT) is another blood test that can be used to detect Down’s syndrome. This screening test is not currently offered by the NHS, however some NHS Trusts have piloted the test and a number of maternity units do offer testing privately.

Early dating scans

All women will be offered a dating scan and an 18–20 week mid-pregnancy or fetal anomaly ultrasound scan. The main purpose of a dating scan...