Interpretation of chorionic villus sampling laboratory results is just as reliable as amniocentesis.

Karyotypes of chorionic villi have been said to be less accurate than karyotypes of amniocytes. Karyotypic differences between placental and fetal tissue and maternal-cell contamination could potentially complicate clinical management. We compared cytogenetic results obtained by chorionic villus sampling and amniotic fluid cells in our center during a 2-year period (1986-1987). Chorionic villus sampling material was processed for direct analysis and backed up when indicated (now routinely) with tissue cultures. The incidence of inconclusive results requiring additional studies was 1.2% for chorionic villus sampling and 0.75% for amniotic fluid cells. Mosaicism was the most common problem for both chorionic villus sampling and amniotic fluid cells. Failure of growth was more frequent in amniocentesis material (0.35 versus 0.09%), but polyploidy and atypical aneuploidies were greater with chorionic villus sampling. The accuracy of cytogenetic evaluation by chorionic villus sampling and amniotic fluid cells and the need for additional invasive procedures appear to be equal in our laboratory.