Diagnosis of chromosomal defects
Screening tests give a personalized statistic of the chance that the fetus would have a chromosomal defect, such as Down syndrome
- To be certain if the fetus has a chromosomal defect or not it is necessary to carry out amniocentesis or chorionic villous sampling (CVS). However, these tests are invasive and they can cause a miscarriage
- The information obtained from amniocentesis and CVS is the same and the risk of miscarriage from both methods is 1%
- Amniocentesis should be performed after 15 weeks because with earlier amniocentesis the rate of miscarriage is increased by about 2% and the chance of delivering a baby with club feet is increased by 1.5%
- CVS should not be performed before 11 weeks because earlier CVS could cause amputations of the limbs
- Invasive tests should be carried out by appropriately trained and experienced operators
Amniocentesis
CVS