: media-1vid110.1542/5804915133001PEDS-VA_2018-0648Video Abstract BACKGROUND AND OBJECTIVES: In a recent Danish study, researchers found an increased risk of childhood epilepsy after phototherapy but only in boys. We investigated this association in a Kaiser Permanente Northern California cohort. From 499?642 infants born at ?35 weeks’ gestation in 1995-2011 followed for ?60 days, we excluded 1773 that exceeded exchange transfusion thresholds and 1237 with seizure diagnoses at <60 days. We ascertained phototherapy, covariates, and outcomes from electronic records and existing databases. Our primary outcome was ?1 encounter with a seizure diagnosis plus ?1 prescription for an antiepileptic drug. We used Cox and Poisson models to adjust for bilirubin levels and other confounding variables. A total of 37?683 (7.6%) infants received any phototherapy. The mean (SD) follow-up time was 8.1 (5.2) years. The crude incidence rate per 1000 person-years of the primary outcome was 1.24 among phototherapy-exposed children and 0.76 among those unexposed (rate ratio: 1.63; 95% confidence interval [CI]: 1.44 to 1.85). The adjusted hazard ratio (aHR) was 1.22 (95% CI: 1.05 to 1.42; P = .009). Boys were at higher risk of seizures overall (aHR = 1.18; 95% CI: 1.10 to 1.27) and had a higher aHR for phototherapy (1.33; 95% CI: 1.10 to 1.61) than girls (1.07; 95% CI: 0.84 to 1.37), although effect modification by sex was not statistically significant (P = .17). The adjusted 10-year excess risks per 1000 were 2.4 (95% CI: 0.6 to 4.1) overall, 3.7 (95% CI: 1.2 to 6.1) in boys, and 0.8 (95% CI: -1.7 to 3.2) in girls. Phototherapy in newborns is associated with a small increased risk of childhood seizures, even after adjusting for bilirubin values, and the risk is more significant in boys.