Childhood food insecurity endangers child development and health outcomes. Food insecurity will grow increasingly common in the economic wake of the coronavirus pandemic and prenatal care represents an early, clinical opportunity to identify families at risk. However, longitudinal relationships between clinically-identified prenatal food insecurity and prematurity, pediatric health care utilization, and postnatal social needs have not been described. We examined longitudinal data from mother-child dyads who received prenatal and pediatric care and social needs screening at a large academically-affiliated safety net medical center between October 2018 and July 2019. Associations among household food insecurity and premature birth, pediatric inpatient and outpatient utilization, missed immunizations, and postnatal social needs were estimated using adjusted regression. Among the 268 mothers, those who experienced prenatal household food insecurity had 3 times higher odds of having a child born prematurely (95% confidence interval [CI] 1.0-8.9, P = .05) and had children with higher inpatient hospitalizations (incidence rate ratio [IRR] 2.4, 95% CI 1.0-5.6, P = .04) and missed immunizations (IRR 3.4, 95% CI 1.1-10.3, P = .03) in the first 6 months of the child's life. These mothers also had higher odds of having any social needs in the pediatric setting (odds ratio 3.4; 95% CI 1.5-8.0, P = .004). Prenatal household food insecurity was linked to future adverse perinatal and pediatric outcomes in low-income mother-child dyads. Food insecurity identifies children at social and medical risk, providing an early clinical opportunity to intervene. Copyright © 2020 Academic Pediatric Association. Published by Elsevier Inc. All rights reserved.