BACKGROUNDThe true risk of chronic villus sampling (CVS) is poorly defined. The objective of this study was to review the clinical outcome of transabdominal CVS performed in a university teaching unit, with an emphasis on the complication rate.

METHODSA comprehensive audit database was maintained for 1,351 pregnant women, including 17 sets of twin pregnancies, who had a CVS. Details and outcome of all CVSs made in the unit between May 1996 and May 2004 were reviewed. All CVSs were performed by one of 5 operators using the identical techniques.

RESULTSAll procedures were performed transabdominally. A total of 1,355 CVSs were performed because there were 4 dichorionic twin pregnancies which required 2 punctures. The mean gestation at CVS was (11.8 +/- 0.7) weeks, and 97.3% of the procedures were performed between 11 and 13 completed weeks. The majority (96.2%) required only 1 puncture to achieve correct needle placement. The procedure failed to obtain an adequate sample in 4 subjects (0.30%). A total of 1,351 chromosomal studies were requested and there was 1 case (0.07%) of culture failure. The results of chromosomal studies were available within 14 days in 36.7% of the cases and within 21 days in 94.0%. Overall, 77 chromosomal abnormalities (5.7%) and 5 cases of thalassemia major were detected. Pregnancy outcome was unknown in only 13 singleton subjects (0.96%). In the remaining 1,355 fetuses, there were 76 pregnancy terminations (5.56%), 10 fetal losses with obvious obstetric causes (0.73%), and 21 potentially procedure-related fetal losses (1.54%). In the last group, the majority had one or more co-existing obstetric complications. The background fetal loss rate for pregnancies at similar gestational age in the unit was about 0.8%. Therefore, the procedure-related fetal loss rate was estimated to be at the maximum of 0.74%.

CONCLUSIONSIn experienced hands, first trimester transabdominal CVS is an accurate and safe invasive prenatal diagnostic procedure. It should be one of the treatment options available to pregnant women who require prenatal genetic diagnosis.