Background: Past studies in high-income countries have shown an association between unintended (unwanted or mistimed) pregnancy and child development; no national-level studies in low-and-middle-income countries have been conducted. Moreover, extant studies often adjust for potential mediators, underestimating the average population effect. Methods: We aimed to estimate the effect of unintended pregnancy on early childhood development in Ecuadorian children aged 3 to 5, participating in the National Health and Nutrition Survey 2018. We used a design-based doubly robust estimate. First, we used propensity score matching to identify a subsample equally likely to come from a desired vs. unintended pregnancy. Then, we used a regression model to explore the relation of maternal pregnancy intentions with early development. Results: Among 1,694 observations representing 162,285 Ecuadorian children, unintended pregnancy associated with developmental delays (odds ratio: 1.56; 95% confidence interval: 1.06; 2.29), after adjusting for all relevant confounders. Unintended pregnancy was also negatively associated with all four early childhood development index domains, socio-emotional development being the most affected. Discussion: Our doubly robust design found evidence of the relation between the maternal perception of pregnancy and early child development. Addressing this relation to achieve reproductive justice entails considering a wide spectrum of population health and legal interventions to allow adequate access to education, contraception, and safe abortion. Moreover, pre-and post-natal check-ups could screen for unintended pregnancy and provide support accordingly.