Section 7 - Invasive tests

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What is chorionic villus sampling (CVS)?

CVS is a procedure during which a hospital doctor (obstetrician) removes a small amount of tissue from your placenta (afterbirth) during your pregnancy. The cells in this tissue are tested in the laboratory to look for the condition that you are higher chance for. You can usually have CVS after you are 11 weeks and before 14 weeks pregnant.

Having a CVS carries a risk of miscarriage which is likely to be below 0.5% of pregnancies (around 1 in 200). The risk of miscarriage following CVS in a twin pregnancy is around 1% of pregnancies (1 in 100).
 

What is amniocentesis?

An amniocentesis is a procedure to remove about 15 to 20 millilitres (that is, three to four teaspoons) of amniotic fluid from around your baby in the womb. The cells from your baby that are floating in this fluid can be tested in the laboratory to look for the condition that you are higher chance for. It can be done after you are 15 weeks pregnant.

Having an amniocentesis carries a risk of miscarriage which is likely to be below 0.5% of pregnancies (around 1 in 200). The risk of miscarriage following amniocentesis in a twin pregnancy is around 1% of pregnancies (1 in 100).