Genetic diagnosis in multiple pregnancies: Amniocentesis versus chorionic villus sampling

The likelihood of finding chromosomal anomalies and Mendelian diseases is increased in multiple gestations compared to singletons. Prenatal diagnosis may therefore be indicated in multiple pregnancies at least as often as in singleton gestations. Invasive testing using amniocentesis or chorionic villus sampling has similar margins of safety. Chorionic villus sampling has a significant advantage over amniocentesis, because it offers rapid karyotyping and biochemical or DNA studies at an earlier stage of pregnancy. However, only experienced centers should perform these procedures, because of the technical aspects of the procedures as well as the expertise needed in the interpretation and handling of discordant results.