Diagnostic tests - Amniocentesis and CVS (chorionic villus sampling)

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 serum screening (blood test) has suggested the baby is at higher risk, or because ultrasound screening has detected 'soft markers' or signs of a chromosome abnormality.  

Though both tests are used to look for chromosomal conditions such as Down's, Patau's and Edwards' syndromes, the amnio can also diagnose other anomalies such as neural tube defects. 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.

The CVS test, which is usually done from about 10-13 weeks, involves taking a sample of the baby's 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 'Information' section - Diagnositic tests and also Healthtalkonline - Antenatal Screening website 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.  

She was not expecting to have to make a decision about which test to chose (she chose CVS) and describes how her feelings about these tests changed once she realised her baby had problems.

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.

She describes having an amnio and says that the procedure went well and that she experienced little discomfort at the time or soreness afterwards.

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.  

She explains why she had several CVS tests done and how anxious she felt at the time.

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.

She has never worried about amnios because she has always been cared for by experienced staff in a large teaching hospital.

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. (The latest 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).  

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.  

Describes how the consultant encouraged her to look at the baby on the screen as he was doing the amnio.

She had no painkilling injection before the amnio and was told to expect 'mild discomfort' which she felt was rather misleading.

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. 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.  

She had been told after her amnio that her baby didn't have Downs' but hadn't realised that the amnio could also detect 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.  

Describes how she heard the results of the amnio on the phone and that it was difficult to cope because she was on her own with the children.

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.