Adverse pregnancy outcomes in successive pregnancies and maternal cardiovascular mortality: a Norwegian nationwide study

BACKGROUND AND AIMS: Binary classification of adverse pregnancy outcomes (APOs) may obscure differences in women's long-term cardiovascular disease (CVD) mortality. CVD mortality was therefore evaluated considering APO sequence and lifetime parity. METHODS: A total of 1 001 409 women with complete pregnancy histories were identified from the Medical Birth Registry of Norway (1967-2020) and linked to the Norwegian Cause of Death Registry for premature CVD mortality (≤70 years). Pregnancy histories were categorized by lifetime parity (1 vs ≥2) and APO sequence (first vs later) for composite APO, and APO recurrence type (same vs different) for individual APOs-preeclampsia, gestational hypertension, preterm delivery, perinatal loss, small for gestational age, placental abruption-multiparous women without APOs as reference, compared with binary classification (APO presence vs absence). Hazard ratios (HRs) were estimated using Cox proportional hazards models. RESULTS: For composite APOs, women with APOs in first pregnancy and no further pregnancies had the highest CVD mortality [adjusted HR (aHR) 3.30, 95% confidence interval (CI) 2.97-3.66], followed by those with APOs in both first and later pregnancies (aHR 2.41, 95% CI 2.16-2.69). Women with APOs in later pregnancies only (aHR 1.65, 95% CI 1.50-1.81) and women with only one pregnancy without complications (aHR 1.83, 95% CI 1.69-1.97) had moderate CVD mortality. Women with APOs in first pregnancy followed by uncomplicated pregnancies (aHR 1.39, 95% CI 1.27-1.53) had the lowest CVD mortality. Binary classification indicated an overall 1.73-fold higher CVD mortality (95% CI 1.64-1.84). Similar patterns were observed across individual APOs. CONCLUSIONS: Considering APO sequence across complete pregnancy histories provides more detailed CVD information than binary classification.