Triple/ double test

The triple test is carried out at 16 weeks to measure the levels of three substances produced by the mother and the placenta. The levels change during pregnancy and a higher level could indicate that the baby may have Down's syndrome or spina bifida.

The test cannot confirm that the baby is affected but it does indicate whether further tests, such as amniocentesis, are required.

Not all areas use the triple test; some offer the double test, where two substances are measured; other hospitals don't offer the test at all, but you can have it done privately.