ad. 27. When to undergo chorionic villus sampling?
Chorionic villus sampling (CVS) can be performed safely after completed 11 weeks of pregnancy (11+0) until delivery. There is no upper limit of gestational age restraining the possibility to carry out the sampling, though the tendency is to perform this examination up to 14 weeks. However, there are situations after 14 weeks, in which chorionic villus sampling is an optimal solution. The oligohydramnios or anhydramnios are good examples. In the following cases, there is no possibility for collecting amniotic fluid or it might be unsafe. In such cases, after 19 weeks umbilical cord blood might be extracted through cordocentesis.