Estimating the spontaneous loss of Down syndrome fetuses between the times of chorionic villus sampling, amniocentesis and livebirth.

Recent publications concerning the prevalence of Down syndrome at times of chorionic villus sampling (CVS), amniocentesis and livebirth were reviewed with particular interest in estimates of spontaneous loss of Down syndrome fetuses during pregnancy. Data from several studies were combined to provide information on 258,206 pregnancies. A logistic regression was applied to provide new estimates and confidence intervals (CIs) for spontaneous loss rates between the time of CVS and livebirth (estimate = 39 per cent; 90 per cent CI 32 to 45 per cent), and the time of amniocentesis and livebirth (estimate = 12 per cent; 90 per cent CI 5 to 18 per cent).