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Sanus Jihlava

Prenatal diagnosis

If a risk of a foetal congenital defect is detected during pregnancy, it is possible to detect or rule out this defect. We distinguish between non-invasive (ultrasound, blood tests) and invasive methods of examination, where foetal tissues obtained by penetration (invasion) of the sampling tool to the foetus are directly examined.

Non-invasive methods

PRENASCAN – non-invasive prenatal test of foetal chromosomal defects – mainly trisomy of chromosome 21 – Down syndrome, chromosome 18 – Edwards syndrome and chromosome 13 – Patau syndrome.

Invasive methods

Placental tissue (CVS) and amniotic fluid (AMC) collection and testing are most commonly performed. CVS – collection of chorionic villi (tissue forming placenta) is performed between week 10 and 13 of pregnancy – a needle is inserted through the abdominal wall under ultrasound control. Local skin anaesthesia is performed before the collection. The target is the base of the placenta. The collection needle avoids the foetus and amniotic fluid. Approximately 15-20 mg of tissue is collected. AMC-collection of amniotic fluid is most often performed around week 16 of pregnancy.

Amniotic fluid (AF) is a clear fluid containing both free biochemicals and living foetal cells. Sampling is performed with ultrasound visualisation through the abdominal wall with a very thin needle (about 0.5 mm in diameter). The physician will be able to clearly see the tip of the needle throughout the collection, so injury to the foetus is very unlikely. Pregnant women report pain comparable to blood collection or a regular injection. Approximately 15-20 ml of AF is collected. This small amount will be replenished within a few hours after the collection.

Risk of complications of foetal tissue collection

The most serious complication of pregnancy associated with collection is miscarriage. The risk reported in the literature is about 0.5% (1/200) above the baseline miscarriage risk for each pregnancy. However, the real risk of foetal tissue collection is difficult to determine. The basic risk of miscarriage between week 16 and 20 is around 1-2%, depending on the mother's age, regardless of whether the collection was performed. It is not possible to create a control cohort of pregnant women at risk of foetal injury, who would be randomly chosen into the control group without the possibility of diagnostic examination. Ergo, the risk of complications is only estimated inaccurately with different results.

The result of chromosomal analysis (chorionic villi or amniotic fluid cells using AmnioPCR) is known within 24 hours of collection. The complete chromosomal examination (karyotype) takes about 2 weeks.