Chorionic villus sampling.

Chorionic villus sampling (CVS) has the great advantage over mid-trimester amniocentesis of producing early results. Moreover, rapid analytic techniques have significantly reduced the waiting time between sampling and diagnosis, whereas progress in recombinant DNA technology and human gene mapping has led to an increase in the range of conditions it can detect. The role of CVS in twin pregnancy has been investigated and compared with amniocentesis. Although these techniques are equally safe, CVS should be considered the approach of choice because of a number of technical advantages, and in relation to selective fetal reduction in discordant twins. Confined placental mosaicism has been investigated and a list of chromosomes related to adverse pregnancy outcome has been compiled. Recent reports have substantially contributed to solving the controversy on the hypothetical relationship between limb reduction defects and CVS. Analysis of limb reduction defects among more than 130,000 cases reported to the World Health Organization CVS registry has been unable to find any relationship between sampling and fetal malformations, including limb reduction defects.