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

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.

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.

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.

Considering APO sequence across complete pregnancy histories provides more detailed CVD information than binary classification.