Limited access to healthy foods, resulting from residence in neighborhoods with low food access or from household food insecurity, is a public health concern. Contributions of these measures during pregnancy to birth outcomes remain understudied.We examined associations of neighborhood food access and individual food insecurity during pregnancy with birth outcomes.We used data from 53 cohorts participating in the nationwide Environmental influences on Child Health Outcomes (ECHO)-Wide Cohort Study. Participant inclusion required a geocoded residential address or response to a food insecurity question during pregnancy and information on birth outcomes. Exposures include low-income-low-food-access (LILA, where nearest supermarket is >0.5 miles for urban or >10 miles for rural areas) or low-income-low-vehicle-access (LILV, where few households have a vehicle and >0.5 miles from the nearest supermarket) neighborhoods and individual food insecurity. Mixed-effects models estimated associations with birth outcomes, adjusting for socioeconomic and pregnancy characteristics.Among 22,206 pregnant participants (mean age 30.4 years) with neighborhood food access data, 24.1% resided in LILA neighborhoods and 13.6% in LILV neighborhoods. Of 1,630 pregnant participants with individual-level food insecurity data (mean age 29.7 years), 8.0% experienced food insecurity. Residence in LILA (vs. non-LILA) neighborhoods was associated with lower birth weight (β -44.3 grams; 95% CI -62.9, -25.6), lower birth weight-for-gestational-age z-score (-0.09 SD units; -0.12, -0.05), higher odds of small-for-gestational-age (OR 1.15; 95% CI 1.00, 1.33), and lower odds of large-for-gestational-age (0.85; 95% CI 0.77, 0.94). Similar findings were observed for residence in LILV neighborhoods. No associations of individual food insecurity with birth outcomes were observed.Residence in LILA or LILV neighborhoods during pregnancy is associated with adverse birth outcomes. These findings highlight the need for future studies examining whether investing in neighborhood resources to improve food access during pregnancy would promote equitable birth outcomes.