OBJECTIVE: Postterm delivery is a risk factor for perinatal complications, some of which increase risk for neurologic morbidity. We aimed to examine the association between postterm delivery and risk for epilepsy in childhood. METHODS: We conducted a cohort study of singleton children who were born in 3 Danish counties from 1980 to 2001. Birth registry data were linked with hospital records to identify cases of epilepsy in the first 12 years of life. We included children who were born at 39 gestational weeks and computed crude, agespecific, and birth weight standardized incidence rates of epilepsy. We estimated adjusted incidence rate ratios according to mode of delivery by Poisson regression. RESULTS: Among the 277 435 nonpreterm births, 32 557 were at 42 weeks, including 3396 at 43 weeks. Nearly one fourth of the 2805 epilepsy cases occurred in the first year of life. In that period, birth weight standardized incidence rate ratios for epilepsy were 1.3 for birth at 42 weeks and 2.0 for birth at 43 weeks, compared with birth at 39 to 41 weeks. Among children who were delivered by cesarean section, incidence rate ratios adjusted for birth weight, presentation, malformations, and county were 1.4 for birth at 42 completed weeks and 4.9 for birth at 43 weeks, compared with term vaginal births. There was a similar tendency among children who were delivered with the assistance of instruments. We found no evidence for the association between postterm delivery and risk for epilepsy beyond the first year of life. CONCLUSIONS: Prolonged gestation is a risk factor for early epilepsy; the added increase in risk for instrument-assisted and cesarean deliveries could be attributable to factors that are related to both birth complications and epilepsy.
