Sometimes your Lead Maternity Carer may recommend additional testing for chromosomal abnormality. There are several options which may be recommended, depending on the gestation period.

Many fetuses, which may have been identified as possible high risk following Nuchal Transparency Measurement, will in fact be proven to be normal on further testing.

CHORIONIC VILLUS SAMPLING (CVS) AT 11 TO 14 WEEKS
CVS is the most test most commonly offered at 11 to 14 weeks gestation. It involves the examination of chorionic villi (placental fragments). Both the baby and the placenta develop from the same cell. That is why the cells of the placenta can be used to check the chromosomes of the baby. There is a very minimal risk of miscarriage due to CVS (around 1%). This is similar to amniocentesis at 15 weeks. The CVS procedure is never performed before 11 weeks.

Before CVS
A local anaesthetic will be given.

CVS
A fine needle is passed into the uterus through the mother’s abdomen and a sample of choronic villi is taken. The needle is watched closely with an ultrasound scan to ensure it does not injure the fetus.

Post-CVS
The results will be available within 2 to 3 weeks and will be sent to your Lead Maternity Carer.
In approximately 1% of cases, the invasive test will need to be repeated. This is because the cells will not grow in the laboratory or the results are inconclusive.

AMNIOCENTESIS AT 15 TO 17 WEEKS
Amniocentesis is an alternative invasive test which involves passing a thin needle into the uterus to take some fluid from around the fetus. This test gives the same information as CVS but is carried out at 15 weeks. The risk of miscarriage is very low at about 1%.

Before  Amniocentesis
A local anaesthetic will be given.

Amniocentesis
A fine needle is passed into the uterus through the mother’s abdomen and a sample of fluid from around the fetus is taken. The needle is watched closely with an ultrasound scan to ensure it does not injure the fetus.

Post-Amniocentesis
The results will be available within 3 weeks and will be sent to your Lead Maternity Carer.

CORDOCENTESIS AT 20 TO 24 WEEKS
Cordocentesis is a further test for chromosome abnormality and is carried out at 20 to 24 weeks gestation. It involves taking some blood from the umbilical cord by inserting a think needle into the uterus. The procedure carries a low risk of miscarriage of about 1%.

Before  Cordocentesis
A local anaesthetic will be given.

Cordocentesis
A fine needle is passed into the uterus through the mother’s abdomen and a sample of blood from the umbilical cord is taken. The needle is watched closely with an ultrasound scan to ensure it does not injure the fetus.

Post-Cordocentesis
The results will be available within 3 weeks and will be sent to your Lead Maternity Carer.