Limb defects and chorionic villus sampling: results from an international registry, 1992-94

Background Several reports of limb defects occurring among infants exposed to chorionic villus sampling (CVS) during pregnancy resulted in concern about the safety of this procedure for prenatal diagnosis. To avoid publication bias and evaluate the true risk of limb defects in a CVS cohort, the World Health Organization initiated international registration of post-CVS limb defects in 1992. Methods From May, 1992, to May, 1994, 77 infants or fetuses with limb defects from 138 996 pregnancies having CVS were reported to the WHO CVS Registry. These cases were analysed by standardised methods-ie, exclusion of syndromes, inherited disorders, and defects occurring in previable fetuses. The included limb deficiencies were studied by pattern analysis. Findings Defects of the upper limbs were reported in 64·6%, of the lower limbs in 12·5%, and of both upper and lower limbs in 20·8% of cases. These figures are in agreement with the distribution of limb defects in several large population-based studies. Transverse limb defects occurred in 40·8% and longitudinal defects in 59·2%, compared with 42·7% and 57·3% in an unexposed population. Interpretation The analysis of this cohort did not show any differences from the background population in the overall frequency or pattern distribution of limb deficiencies. There was also no correlation between gestational age at CVS and severity of defects. Therefore these results do not indicate any increased risk of limb defects after CVS.