If you or your partner become pregnant and both have beta thalassaemia trait, you will be offered a choice of tests on your baby in the womb. There are 3 tests. One is Chorionic villus sampling (CVS) where a sample of the placenta is taken by inserting a needle, either through the wall of your tummy or through a tube placed in your vagina. The sample contains exactly the same genes as your baby and can be taken early in pregnancy. A second test is amniocentesis where a sample of the amniotic fluid that surrounds your baby is taken by inserting a needle through the wall of your abdomen. Lastly, a foetal blood sampling where a sample of blood is taken from the umbilical cord. This is usually only done if the placenta can't be reached easily or if previous tests haven't produced a clear picture.
Attribution: BUPA