BACKGROUND: The first 1000 days of life are a critical period when the foundations of child development and growth are established. Few studies in Latin America have examined the relationship of birth outcomes and neonatal care factors with development outcomes in young children. We aimed to assess the association between pregnancy and neonatal factors with children's developmental scores in a cross-sectional, population-based study of children in Ceará, Brazil. METHODS: Population-based, cross-sectional study of children aged 0-66 months (0-5.5 years) living in Ceará, Brazil. We examined the relationship of pregnancy (iron and folic acid supplementation, smoking and alcohol consumption) and neonatal (low birth weight (LBW) gestational age, neonatal care interventions, and breastfeeding in the first hour) factors with child development. Children's development was assessed with the Ages and Stages Questionnaire (ASQ-BR). We used multivariate generalized linear models that accounted for clustering sampling to evaluate the relationship of pregnancy and neonatal factors with development domain scores. FINDINGS: A total of 3566 children were enrolled. Among pregnancy factors, children whose mothers did not receive folic acid supplementation during pregnancy had lower fine motor and problem-solving scores (p-values< 0.05). As for neonatal factors, LBW was associated with 0.14 standard deviations (SD) lower (CI 95% -0.26, - 0.02) communication, 0.24 SD lower (95% CI: - 0.44, - 0.04) fine motor and 0.31 SD lower (CI 95% -0.45, - 0.16) problem-solving domain scores as compared to non-LBW children (p values < 0.05). In terms of care, newborns that required resuscitation, antibiotics for infection, or extended in-patient stay after birth had lower development scores in selected domains. Further, not initiating breastfeeding within the first hour after birth was associated with lower gross motor and person-social development scores (p-values < 0.05). CONCLUSION: Pregnancy and neonatal care factors were associated with later child development outcomes. Infants at increased risk of suboptimal development, like LBW or newborns requiring extended in-patient care, may represent groups to target for supplemental intervention. Further, early integrated interventions to prevent adverse pregnancy and newborn outcomes may improve child development outcomes.