External validation of first trimester combined screening for pre-eclampsia in Brazil: An observational study

•Prior validation of predictive algorithms is paramount to implementation of such predictive tools in clinical practice.•Prediction of PE with algorithms is feasible and outperforms the use of clinical risk factors alone.•Proper evaluation of screening performance requires adjustment for the effect of aspirin. To validate a combined algorithm for early prediction of pre-eclampsia (PE) in the Brazilian population. This is an unplanned secondary analysis of a cohort study. Consecutive singleton pregnancies undergoing first-trimester screening for PE involving examination of maternal characteristics, medical history, and biophysical markers were considered eligible. Women were classified as low-or high-risk using a cutoff of 1/200, but the individual risk was not used to dictate management, as aspirin prophylaxis was given to women based solely on clinical risk factors. Receiver-operating characteristics (ROC) curves for PE, preterm PE(PE