Cohort profile: the Cohort for Risk Prediction Model Evaluation (CORE) for external validation of models identifying high-risk pregnant women in the early second trimester, North India

Purpose: The Cohort for Risk Prediction Model Evaluation (CORE) was established to externally validate prediction models that identify high-risk pregnancies in the early second trimester. Such models are often developed on small, single-source datasets and seldom tested elsewhere. Recent evidence shows that only about 6-10% models are ever externally validated which raises concerns about whether they perform reliably in new and diverse populations. In the maternal perinatal space, CORE addresses this gap by providing an Indian second-trimester cohort with harmonised imaging and outcome data on which existing risk prediction models can be validated. Participants. CORE includes 964 pregnant wo