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Prenatal diagnostic tests

If a screening test shows an increased chance of a genetic condition  expectant mothers can choose

to have a diagnostic test to confirm if the condition is definitely present in the pregnancy of not.

When deciding whether to go ahead with diagnostic testing, it is important to weigh up the risks vs the benefits of the test and to think about whether the result will change your decisions about the pregnancy. This will be different for each individual and your midwife, obstetrician and/or genetic counsellor can help you to think about what feels like the best option for you personally. The two types of diagnostic tests for KS in pregnancy are a CVS and an amniocentesis.

Chorionic villus sampling (CVS)

Similar to an amniocentesis, CVS is a diagnostic test for chromosomal abnormalities. This procedure involves collection of a small sample of cells taken from the placenta which supplies blood from a mother to her baby. CVS can be typically carried out earlier in the second trimester than amniocen-tesis, between the 11th and 14th weeks of pregnancy. A CVS is thought to have a similar miscarriage risk to having an amniocentesis


Amniocentesis is typically carried out in the second trimester between the 15th and 20th week of pregnancy. It involves collection of a small sample of cells from the fluid within the protective sac that surrounds the unborn baby in the womb, called the amniotic fluid. The cells are collected by inserting using a long, thin needle through the abdominal wall into the amniotic sac. The doctor us-es ultrasound imaging to guide them. The process usually takes about 10 minutes and is often re-ported as uncomfortable but not painful. Results from the test can take a couple of days to a few weeks to come back. Having an amniocentesis is thought to slightly increase the chance of having a miscarriage by about 1%.