Adverse Pregnancy Outcomes and Long-Term Risk of Atrial Fibrillation.

Importance Women with adverse pregnancy outcomes have higher subsequent cardiovascular risks, but their long-term risk of atrial fibrillation (AF) and potential causality are unclear. A better understanding of such risks is needed to identify women with high risk early in life and guide interventions to prevent AF and its complications. Objective To determine long-term risks of AF associated with 6 major adverse pregnancy outcomes in a large population-based cohort and assess for familial confounding using cosibling analyses. Design, Setting, and Participants This national cohort study included all women with a singleton delivery in Sweden between 1973 and 2015. Analyses were conducted between May 23 and August 18, 2025. Exposures Adverse pregnancy outcomes (preterm delivery, small for gestational age, large for gestational age, preeclampsia, other hypertensive disorders, and gestational diabetes), identified from nationwide birth records. Main Outcome and Measures The primary outcome was AF identified from nationwide inpatient and outpatient diagnoses through 2018. Cox regression was used to compute hazard ratios (HRs) for AF associated with specific adverse pregnancy outcomes, adjusting for other maternal factors. Cosibling analyses assessed for potential confounding by shared familial (genetic and/or environmental) factors. Results Among 2 201 047 women with 54 million person-years of follow-up, 51 173 (2.3%) were diagnosed with AF (median [IQR] age at diagnosis, 63 [56-69] years). All adverse pregnancy outcomes except small for gestational age were associated with long-term increased risks of AF. Within 10 years following delivery, adjusted HRs for AF were significantly elevated only among women with other hypertensive disorders (HR, 1.69; 95% CI, 1.32-2.15), preterm delivery (HR, 1.46; 95% CI, 1.26-1.70), or large for gestational age (HR, 1.16; 95% CI, 1.01-1.32). However, at 30 to 46 years after delivery, adjusted HRs were increased among women with other hypertensive disorders (HR, 1.44; 95% CI, 1.24-1.66), preeclampsia (HR, 1.38; 95% CI, 1.33-1.50), gestational diabetes (HR, 1.19; 95% CI, 1.03-1.37), large for gestational age (HR, 1.17; 95% CI, 1.14-1.21), or preterm delivery (HR, 1.11; 95% CI, 1.07-1.16). These findings were largely unexplained by shared familial factors. Women with multiple adverse pregnancy outcomes had further increases in risk. Conclusions In this large national cohort, all adverse pregnancy outcomes except small for gestational age were associated with increased risk for AF up to 46 years later. Women with adverse pregnancy outcomes need early preventive actions and long-term clinical follow-up for timely detection and treatment of cardiovascular disorders related to the development of AF.