Abstract
BACKGROUND: Amniocentesis test results are usually available only after 18 weeks gestation. Chorion villus sampling (CVS) may be performed transabdominally or transvaginally, usually between 10 and 12 weeks gestation. OBJECTIVES: The objective of this review was to assess the safety and accuracy of chorion villus sampling compared to amniocentesis. SEARCH STRATEGY: We searched the Cochrane Pregnancy and Childbirth Group trials register. SELECTION CRITERIA: Randomised trials comparing first trimester chorion villus sampling and second trimester amniocentesis. DATA COLLECTION AND ANALYSIS: Trial quality was assessed. MAIN RESULTS: Three studies involving over 9000 women were included. The trials were generally of good quality. Compared to amniocentesis, chorion villus sampling was associated with more sampling and technical failures, and more false positive and false negative results. Pregnancy loss was more common after chorion villus sampling (odds ratio 1.33, 95% confidence interval 1.17 to 1.52). There is a suggestion (though not statistically significant) of an increase in stillbirths and neonatal deaths following chorion villus sampling. Maternal complications were uncommon. REVIEWER'S CONCLUSIONS: The increase in miscarriages after chorion villus sampling compared to amniocentesis appear to be procedure related. Second trimester amniocentesis appears to be safer than chorion villus sampling. The benefits of earlier diagnosis with chorion villus sampling must be set against the greater risk of pregnancy loss.