Sampling success and risk by transabdominal chorionic villus sampling, transcervical chorionic villus sampling and amniocentesis: a randomized study

A total of 3347 women were randomized to either transabdominal chorionic villus sampling, transcervical chorionic villus sampling or amniocentesis. Unless induced or spontaneous abortion had occurred, they had all completed up to 28 weeks of pregnancy at the time of analysis. No significant difference was seen between total fetal loss in the transabdominal chorionic villus sampling group and the amniocentesis group (6.2% and 6.6%, respectively, SE difference 0.92%, p = 0.01). The total fetal loss in the transcervical group was 10.1%. When the number of failed procedures and those cases which were evaluated as infeasible for the assigned method, are compared, the overall sampling efficacy is less good transcervically than transabdominally. After pooling our data with data from the Canadian randomized study and the American non-randomized study, the difference in risk between transcervical chorionic villus sampling and amniocentesis was 2.1%, SE difference = 0.64%, p = 0.8.