Ending a pregnancy for fetal abnormality

Diagnostic tests - amnio and CVS

Amniocentesis and CVS are two diagnostic tests that will usually be offered to women during the third and fourth months of pregnancy if there is some concern there may be something wrong with the baby. This may be because a Down’s syndrome screening test has suggested the baby is at higher risk, or because ultrasound screening has detected  signs that may indicate a chromosome abnormality.  

Both tests are used to look for chromosomal conditions such as Down's, Patau's and Edwards' syndromes. Amnios and CVS provide a definite diagnosis, which screening alone cannot, though parents may have to wait days and sometimes weeks to get back every result from the test. Both procedures carry a small risk of causing a miscarriage. The overall risk of you having a miscarriage after CVS is about 1 to 2%. In other words, about one or two in every 100 women who have CVS will miscarry. For amniocentesis, the rate is about one in 100. These figures vary slightly from hospital to hospital.” (Screening Tests for You and Your Baby - Public Health England July 2017) 

The CVS test, which is usually done from about 10-13 weeks, involves taking a tiny sample of tissue from the  placenta. Amnios, usually done around 15-18 weeks, involve taking a small sample of amniotic fluid, the protective fluid round the baby. (For more detailed information see 'Resources' and also 'Antenatal Screening' for more personal experiences of amnios and CVS as well as information about AFP and blood tests.)

Women expressed a range of views about these tests; some felt that they needed to know more about what was wrong with the baby, others were more cautious about the tests and found it hard to make an informed decision about the tests in the time available.  

Most women willingly followed the advice of health professionals about which test was most appropriate for their baby's problems. Many women felt the tests were well worth having and said that they were reassured by seeing the baby on the scan as they had the test, and how health professionals tried to put them at ease during the procedure itself.

Sometimes one test was more appropriate for the baby than another - for example a woman who was expecting non-identical twins had a CVS so that samples were taken from the placentas of both her babies to test which of them had Down's syndrome.  

Many women felt reassured about having the test because they knew (or found out) that the test would be done by an experienced consultant or in a teaching hospital where they felt that clinicians would have had plenty of practice.

A few women said they had found it difficult to make a decision about the tests because of concerns about the risk of miscarriage - several women had been told that an amnio carried a slightly lower risk than the CVS. (Research indicates that on average about 1% of women who undergo amnio or CVS miscarry and that there is now very little difference in terms of risk between CVS and amnio - see Screening Tests for You and Your Baby - Public Health England July 2017).  

Although most women didn't like the idea of having a test that many described as 'invasive', most women took the view that and it was worth having 'a few minutes of discomfort' to find out what was wrong with the baby. However, several women were surprised that the test was more painful than they had been led to expect.  

Waiting for results from amnios and CVS

Waiting for the test results was always an anxious time for parents, and several women talked about finding it difficult to carry on 'as normal' for the sake of their other children. It usually takes 2-3 weeks to get the full results from amnios and CVS tests. However, most centres offer quick results within 3 working days, using the QF-PCR test (which provide a rapid diagnosis of the most common chromosome abnormalities including Down's syndrome, Edwards' and Patau's syndrome). Sometimes parents didn't understand that the baby was being tested for more than Down's syndrome, and so were extremely upset when later test results from the amnio showed the baby had a different chromosome anomaly such as Edwards' syndrome.  

Most women appreciated being visited personally by the midwife and having the news broken to them in person, though several said that they realised the minute they opened the door and saw the midwife that the results confirmed the baby's problems. 

Some women asked if they could be told the test result as soon as possible which meant they had received the news over the phone. Several were on their own at home when they were contacted and told the test result but had had no one to turn to for comfort. One woman described hearing the news of her baby's Down's syndrome over the phone was 'a little bit like being hit over the head with a very large and heavy brick' and said how she had turned to her young son for comfort. Another woman had been given the news on the phone and found she couldn't cope with her young child and felt she needed to ask a neighbour for help.  

Several women said they would have preferred to have had the news of the test results given to them in person, but realised that it was not always possible. Midwives can give the results of the test to people at home, at the antenatal clinic, over the phone or in a letter, this should be discussed with the woman beforehand.

Non Invasive Prenatal Test (NIPT) is another screening test that can be used to detect Down's syndrome. It is a non-invasive test using a maternal blood sample to test free-cell fetal DNA. During pregnancy, fragments of DNA from the placenta called free-cell fetal DNA circulate in the mother’s blood steam. These DNA fragments (CFFDNA) can be genetically tested along with the mother’s blood to show if there is an increase in the number of abnormal chromosomes. 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. The sample has to be sent outside the UK for analysis so the results take about two weeks to come back. The cost of the test varies between clinics (£350 to £550). Large scale studies show that the test has a detection rate of over 99% (ARC July 2017) and also tests for some other common chromosomal anomalies; Edwards syndrome (trisomy 18), Patau syndrome (trisomy 13) and Turner syndrome. It can be performed from 10 weeks of pregnancy and unlike amniocentesis and CVS has no risk of miscarriage. However if the NIPT gives a positive result, an amniocentesis is required for confirmation. For more information see our pregnancy resources. None of the people we interviewed had had this test. 

Last reviewed July 2017.
Last updated July 2017.


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