Sex determination test successful at just seven weeks

A simple blood test for pregnant women can accurately predict the sex of a fetus at seven weeks, much earlier than conventional techniques, new research has found. A systematic review and meta-analysis examined the results of 57 earlier studies that included more than 6,500 pregnancies.

The blood test was accurate 94.8 percent of the time when predicting between seven and 12 weeks that the mother is carrying a boy and 98.9 percent of the time for girls. Tests using urine or taken before seven weeks' gestation were unreliable.

The non-invasive test detects fetal DNA in the mother's blood to see whether it is a girl or boy. Conventional techniques can typically detect gender later in gestation. For example, CVS, ultrasound and amniocentesis are usually done at 10 weeks, 13 weeks and 16 weeks respectively.

The test has been sold privately in several countries for a few years, including the UK. Despite the prior absence of a formal assessment, it has been incorporated into routine clinical care in countries such as the Netherlands, the UK, France and Spain.

The study authors said the blood tests could be a breakthrough for women at risk of having babies with gender-linked disorders, such as haemophilia, which typically affects men. The availability of this reliable non-invasive alternative could reduce the increased risk of miscarriages associated with amniocentesis and CVS, says TIME magazine.

The results of the study, however, should be generalised with caution as the research did not include tests sold directly to consumers, Associated Press reported.

Testing conditions can vary from lab to lab, said Dr Joe Leigh Simpson, a genetics professor at Florida International University who was not involved in the research.  The test also raises ethical concerns about deliberate sex selection of embryos, TIME reports.

'I would have a lot of difficulties offering such a test just for gender identification. Gender is not an abnormality', said Dr Lee Shulman, chief of clinical genetics at Northwestern Memorial Hospital in Chicago. 'My concern is this is ultimately going to be available in malls or shopping centres'.

'If there's a serious or life threatening genetic problem with the fetus, I understand people will want to end this pregnancy and start again', said Professor Arthur Caplan, director of the Center for Bioethics at the University of Pennsylvania. 'But when you're talking about picking a baby's sex, doctors shouldn't offer the test, companies shouldn't offer it, and we should tell people that it's not a good reason to have an abortion'.

The research was published in the Journal of the American Medical Association (JAMA).