Early Life Risk Factors for Incident Atrial Fibrillation in the Helsinki Birth Cohort Study

BACKGROUND: Early life risk factors are associated with cardiometabolic disease, but have not been fully studied in atrial fibrillation (AF). There are discordant results from existing studies of birth weight and AF, and the impact of maternal body size, gestational age, placental size, and birth length is unknown. METHODS AND RESULTS: The Helsinki Birth Cohort Study includes 13 345 people born as singletons in Helsinki in the years 1934–1944. Follow‐up was through national registries, and ended on December 31, 2013, with 907 incident cases. Cox regression analyses stratified on year of birth were constructed for perinatal variables and incident AF, adjusting for offspring sex, gestational age, and socioeconomic status at birth. There was a significant U‐shaped association between birth weight and AF (P for quadratic term=0.01). The lowest risk of AF was found among those with a birth weight of 3.4 kg (3.8 kg for women [85th percentile] and 3.0 kg for men [17th percentile]). High maternal body mass index (≥30 kg/m(2)) predicted offspring AF; hazard ratio 1.36 (95% CI 1.07–1.74, P=0.01) compared with normal body mass index (<25 kg/m(2)). Maternal height was associated with early‐onset AF (<65.3 years), hazard ratio 1.47 (95% CI 1.24–1.74, P<0.0001), but not with later onset AF. Results were independent of incident coronary artery disease, hypertension, or diabetes mellitus. CONCLUSIONS: High maternal body mass index during pregnancy and maternal height are previously undescribed predictors of offspring AF. Efforts to prevent maternal obesity might reduce later AF in offspring. Birth weight has a U‐shaped relation to incident AF independent of other perinatal variables.