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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