Chorion villus sampling and limb deficiency--cause or coincidence?

Chorion villus sampling (CVS) is a widely used technique in first trimester prenatal diagnosis. In the early 1990s, two clusters of babies with limb defects following CVS were reported, raising the possibility of a causal association between early CVS and transverse limb deficiency. The evidence for this association is reviewed and shows a diminishing risk for transverse limb deficiency with advancing gestation. The risk of limb deficiency extends through the period of limb morphogenesis and slightly beyond; falling from levels 10-20-fold above background at nine weeks and below, to levels approaching (or only a few-fold above) background at 11 weeks and beyond.