ArticleOpen heart2026
Maternal cardiac risk stratification in contemporary practice: external validation of mWHO, CARPREG II and ZAHARA in a 14-year tertiary cohort.
Article in Open heart, 2026. The graph could read no effect estimate from its abstract, so it casts no vote on the map. Not yet cited in PubMed.
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Abstract
backgroundPregnancy in women with cardiac disease carries substantial maternal risk. The modified WHO classification, Cardiac Disease in Pregnancy Study II (CARPREG II) and Zwangerschap bij Aangeboren HARtAfwijkingen (ZAHARA; Pregnancy in Congenital Heart Disease) are the three principal risk stratification tools in this setting. External validation in contemporary practice is essential to assess its performance in specialist programmes.
methodsSingle-centre retrospective cohort study of all pregnancies in women with cardiac disease delivering ≥24+0 gestational weeks at a level IV maternal centre between 2009 and 2023. The primary outcome was maternal cardiac complication within 12 months postpartum; the secondary outcome was obstetric complication during pregnancy or the postpartum period. Model accuracy was assessed by comparing the weighted average predicted risk with the observed number of cardiac events, using each scoring system's original published definitions. Additional performance measures included observed-to-expected (O:E) ratios and logistic-regression area under the curve (AUC).
resultsAmong 85 473 deliveries, 407 pregnancies in 282 women were included. The observed maternal cardiac complication rate was 4.18% (17 events); no maternal deaths occurred. All three models overestimate risk: weighted average predicted rates were 12.78% (CARPREG II), 8.3% (mWHO) and 6.7% (ZAHARA), yielding O:E ratios of 0.33, 0.50 and 0.62, respectively. Discrimination was moderate across all scores (AUC 0.69 (95% CI 0.55 to 0.80), 0.69 (95% CI 0.53 to 0.83) and 0.74 (95% CI 0.61 to 0.85) for mWHO, CARPREG II and ZAHARA, respectively. Obstetric complication rates were similar across mWHO classes (8.0%, 7.0% and 7.4% for classes I-III). No score predicted obstetric complications (AUC ≈0.5 for all models).
conclusionsCardiac risk stratification scores might overestimate maternal cardiac risk in this contemporary specialist cohort, consistent with calibration drift, while preserving a clinically meaningful cardiac risk gradient. None captured obstetric risk. These findings highlight the role of individualised assessment. While our findings provide useful preliminary insight, further evaluation in larger and more diverse cohorts is needed to refine risk prediction.
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