Diagnostic invasive procedures

Amniocentesis
A small needle is inserted, under ultrasound guidance, into the amniotic fluid that surrounds the fetus. Some cells from the fetus are in the fluid. These are then either amplified (with a technique known as PCR) and/or cultured, so that the chromosomes in the cells can be looked at. As with all invasive procedures there is approximately 1% risk of miscarriage.

Chorionic villi sampling (CVS)
A small needle is inserted, under ultrasound guidance, into the placenta. The cells in the placenta have the same genes and chromosomes as the fetus. These are then either amplified (with a technique known as PCR) and/or cultured, so that the chromosomes in the cells can be looked at. There are more cells obtained with CVS, compared to amniocentesis, so this technique is usually preferred when looking for genetic anomalies. As with all invasive procedures there is approximately 1% risk of miscarriage.

Cordocentesis (Fetal blood sampling)
A small needle is inserted, under ultrasound guidance, into the umbilical cord of the fetus. The fetal blood cells can then be either amplified (with a technique known as PCR) and/or cultured, so that the chromosomes in the cells can be looked at. There is approximately 1% - 5% risk of miscarriage, depending on the indication for the fetal blood sampling.