Predicting outcome after emergent cerclage using classification tree analysis.

We sought to develop a predictive model for gestational age at delivery after placement of an emergent cerclage in the second trimester. Data were obtained for women undergoing emergent cerclage in response to documented cervical change on physical examination at a university hospital between 1980 and 2000. Hierarchically optimal classification tree analysis (CTA) was used to predict delivery prior to 24 weeks, between 24 and 27 6/7 weeks, or after 27 6/7 weeks. One hundred sixteen women were available for analysis. Delivery prior to 24 weeks was best predicted by presence of prolapsed membranes and gestational age at cerclage placement; delivery between 24 and 27 6/7 weeks was best predicted by parity alone; delivery of at least 28 weeks was best predicted by cervical dilation and length, presence of prolapsed membranes, and parity. When choosing a single model to predict delivery at the three different gestational age periods, the last model yielded the most accurate results. CTA can be used to construct a predictive model for outcome after emergent cerclage that may be informative for both patients and physicians.