Blood test reveals baby's sex in seventh week of pregnancy

Detects foetal DNA in mother's blood

A blood test in the seventh week of pregnancy can accurately determine the sex of the baby, a study has found. The test, which looks for foetal DNA in the mother's blood, was found to be 98 per cent accurate.

Although similar blood tests are on sale in the UK and other European countries, few studies have assessed their accuracy at determining an unborn baby's gender, US researchers said.

The researchers scrutinised the results of 57 studies involving more than 6,000 pregnancies, where "cell-free foetal DNA testing" had been used to identify the gender of the baby. They found that the test was reliable at predicting the sex of the unborn baby 98 per cent of the time as long as it was carried out after seven weeks of pregnancy. Before this, the test was found to be unreliable as there was not enough foetal DNA present in the mother's blood.

All tests using urine instead of blood samples were found to be unreliable, researchers from the National Institutes of Health in Bethesda, Maryland, said.

They said the test could be used to provide reassurance to parents at risk of having a baby with a sex linked genetic disorder, but who don't want amniocentesis because of the small risk of miscarriage.

While non-invasive ultrasound scans can be carried out at 11 weeks, they are not as reliable at predicting a baby's gender. Study leader Dr Stephanie Devaney said: "The availability of a reliable non-invasive alternative to determine foetal sex would reduce unintended foetal losses and would presumably be welcomed by pregnant women carrying foetuses at risk for disorders."

The study is published in the Journal of the American Medical Association.

The Family GP