Invasive prenatal tests

Invasive prenatal tests - when are they performed?

Invasive prenatal tests are not routinely performed on all pregnant women. The gynaecologist recommends them in certain situations. It is recognised that invasive prenatal testing should be done if there is a high (>1:300) risk of trisomy 13/18/21 on first trimester examination. It is also performed if the doctor detects anatomical abnormalities in the child. If the PAPP-A test and ultrasound in the first trimester do not indicate an increased risk of malformations and the baby grows less well in the later weeks of pregnancy, even in the third trimester, for example, a karyotype test using invasive prenatal tests may also be suggested. This way, the professionals know what to expect and their treatment will vary depending on the results.

Invasive prenatal tests - types

Invasive prenatal tests include chorionic villus sampling, cordocentesis and amniocentesis. They differ in the timing of the examination, but also in the material taken. In chorionic villus sampling, as the name suggests, the chorionic villi are taken, in cordocentesis blood is taken from the umbilical cord and in amniocentesis amniotic fluid is taken. The indications for the examination are also different. Cordocentesis is performed when fetal anaemia is suspected and an increased maximum systolic velocity is detected in the middle cerebral artery. If anaemia is diagnosed, a post-fetal transfusion can be performed immediately, which significantly improves the prognosis. This is because anaemia is usually due to serological conflict or parvovirus.

Invasive prenatal tests - are they safe?

The risk of complications associated with invasive prenatal testing is currently estimated at less than 0.5%. The most dangerous of these complications is miscarriage or abortion in the womb. Amniotic fluid leakage or genital spotting may also occur. In extremely rare cases, the baby is injured by the puncture needle. However, complications from invasive prenatal tests are extremely rare. If this type of testing is necessary, it is best to choose a centre with experience in prenatal diagnostics and a specialist who performs similar procedures on a daily basis.