Blood test screening

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:

See also 'Information' section of this website.

Here we concentrate only on tests which screen for conditions in the baby, but many women we talked to were not very sure why their blood was being taken (see 'Information for making decisions'). 

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

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 interests.

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

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 risk 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 and nuchal translucency scan) rather than just the blood test or the nuchal translucency scan on their own. The vast majority of units in England, Scotland and soon Wales now offer combined screening for Down’s syndrome. The blood test measures the levels of two substances in the blood: pregnancy associated plasma protein-A (PAPP-A) and free beta human chorionic gonadotrophin (Free beta hCG).

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 blood sample was damaged in the post.

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 results that alerted them to their baby's condition (Turner's syndrome).

Alternative blood tests - which people are often advised they do not need if they have had a nuchal translucency scan with blood test (combined screening) - are the 'triple test' or the quad (or quadruple) test which check for proteins and hormones in the blood. The triple test measures; hCG (human chorionic gonadotrophin), uE3 (oestriol) and AFP (alpha fetoprotein). The quadruple test measures the same substances as well as the hormone inhibin A. The quadruple test is now offered if a woman is more that 14 weeks + 1 day pregnant and has not had a nuchal translucency scan. Several people did not realise that measuring these substances can assess the risk of neural tube defects such as spina bifida, and one woman described how she turned down this test believing it was only for Down's syndrome. Her baby was later found to have a neural tube defect.

She refused the triple test in her first pregnancy because she did not realise it was for spina bifida as well as Down's syndrome.

 

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

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

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

They decided against blood tests in the current pregnancy and relied only on scans. This time they felt better informed to make a real choice.

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 triple test might make her anxious unnecessarily.

Last reviewed April 2012.

Last updated April 2012.