Urban planning, informal settlements, and maternal health outcomes: Investigating the role of built environment in antenatal and postnatal care utilization in China

China's rapid urbanization has spawned extensive informal settlements, where millions of migrant families live in overcrowded, underserved areas. These environments, characterized by inadequate housing, poor sanitation, unsafe conditions, and limited healthcare access, significantly impede the utilization of maternal healthcare, specifically Antenatal (ANC) and Postnatal Care (PNC). This study examines how built environment characteristics influence ANC and PNC use among women in these settlements across four major Chinese cities. A cross-sectional study collected data from 800 women who had given birth in the previous two years. Built environment elements were measured via subjective assessments and objective indicators, including GPS-based distance to the nearest health facility. Associations were analyzed using multivariate logistic and negative binomial regression models. Findings identify distance to health facilities, housing quality, neighborhood safety, walkability, sanitation, and transport access as critical determinants. Women in disadvantaged settings were less likely to receive adequate ANC or timely PNC. Socio-economic factors -hukou status, education, income, and health insurance- further shaped utilization patterns. The results underscore the necessity of integrating maternal health strategies into urban planning. Improving transport connectivity, upgrading informal settlements, and reducing institutional barriers for migrants are vital to enhancing maternal health and fostering equity in China's rapidly urbanizing landscape.