Maternal hypothyroidism in pregnancy has been associated with cognitive impairment in exposed children. We sought to evaluate the long-term pediatric neurological morbidity of children to mothers with known hypothyroidism during pregnancy. A population-based cohort analysis was performed including all deliveries occurring between 1991-2014 at a regional tertiary medical center. Multiple gestations, fetuses with congenital malformations, and women lacking prenatal care were excluded. Hospitalizations of the offspring up to the age of 18 years involving neurological morbidity were evaluated according to a predefined set of ICD-9 codes, including autistic and developmental disorders, eating, sleeping and movement disorders, cerebral palsy and more. A Kaplan-Meier survival curve was used to compare cumulative hospitalization rate in exposed and unexposed offspring. A Cox regression model was used to control for confounders. During the study period, 217 910 singleton deliveries met the inclusion criteria. Of them, 1.1% (n=2,403) were in mothers with known hypothyroidism during pregnancy. The Kaplan-Meier survival curve demonstrated a significantly higher cumulative incidence of neurological morbidity in the hypothyroidism group (Figure, log rank p=0.007). Specific neurological morbidities in the two study groups are presented in the Table. Most neurological morbidities were comparable between the groups but the total hospitalization rate per person years was significantly higher in the maternal hypothyroidism group (5.5% vs. 3.1%, HR=1.37, 95%CI 1.10-1.73, p=0.007). Using a cox regression model, while controlling for maternal age, birthweight, preterm birth, maternal diabetes, hypertensive disorders of pregnancy, induction of labor, and mode of delivery, maternal hypothyroidism was found to be independently associated with pediatric neurological morbidity in the offspring (adjusted HR=1.3, 95%CI 1.1-1.7, p=0.01). Maternal hypothyroidism in pregnancy is independently associated with long-term pediatric neurological morbidity of the offspring.View Large Image Figure ViewerDownload Hi-res image Download (PPT)