Call to offer amniocentesis to all women

Accurate prenatal tests for Down syndrome and other chromosome disorders should be made available to all pregnant women, not just those over 35, according to a new US study. Researchers at the University of California, San Francisco, evaluated the cost-effectiveness of invasive methods such as amniocentesis, and also surveyed 534 pregnant women aged between 16-47. They concluded that it would be beneficial to offer accurate prenatal testing to all women, regardless of age or level of risk. Guidelines released by the UK's National Institute for Clinical Excellence (NICE) last October stated that all pregnant women, whatever their age, should be offered a non-invasive test for Down syndrome. However, in the UK and many other countries, invasive tests are only offered to women over 35, or those identified as being at higher risk for other reasons.

The cut-off age of 35 was chosen partly because there is a small risk of miscarriage associated with amniocentesis, and also with another invasive technique, called CVS (chorionic villus sampling). It was assumed that there was no benefit in offering these tests to women with a low risk of having an affected baby. But the new study suggests that because womens' personal preferences for prenatal testing varied considerably, offering screening to all women could be cost-effective. For some women, the implications of having a baby with a lifelong problem would outweigh the loss of a wanted pregnancy, according to Mark Evans, US professor of obstetrics and gynaecology. He said that most couples whose results show their child would have a serious chromosomal defect choose to terminate the pregnancy, 'at least here on the East Coast'. The study authors conclude that 'prenatal diagnostic testing should be offered to pregnant women irrespective of maternal age or risk, and guidelines should emphasise the important role of individual preference when making decisions about prenatal diagnostic testing'.

However, in an accompanying commentary, UK health economist Stavros Petrou says that offering such tests to all pregnant women could have 'broader consequences for obstetric and other health services', adding that 'a single economic evaluation provides necessary but insufficient information about the appropriate level of service'. Petrou told New Scientist magazine that while the study was basically sound, the researchers only compared the cost-effectiveness of invasive testing against a 'do-nothing' alternative. But, as he pointed out, there are other, non-invasive tests for Down syndrome available, such as blood tests and ultrasound scans. Such methods could be used to identify those women who would most benefit from the offer of further, invasive tests. Petrou speculated that in a health insurance-based system such as that in the US, 'healthcare providers tend to lack incentive to limit the number of interventions to those that are strictly necessary, because basically the cost is borne by the healthcare insurer'.