BACKGROUND: Inadequate access to quality maternal and child health services leads to poor health outcomes for millions of women, particularly in low- and middle-income countries (LMICs). This study aims to explore the effective coverage of reproductive, maternal, neonatal and newborn health (RMNCH) services and examines socioeconomic and rural and urban disparities in 39 LMICs. METHODS: Using Demographic and Health Surveys (DHS) data, the research assesses RMNCH service quality by applying an effective coverage framework, which measures service contact, crude coverage, quality-adjusted coverage and user adherence-adjusted coverage. We applied weighted analyses to investigate the rural-urban differences in service coverage based on countries' Human Development Index (HDI) levels as well as crude coverage and socioeconomic levels. FINDINGS: Urban areas generally exhibit better effective coverage across all RMNCH services compared with rural areas, with significant disparities in antenatal, childbirth and postnatal care. For instance, 85% (95% CI=85-86%) of urban women received skilled birth attendance compared with 64% (95% CI=64-65%) in rural areas. High-HDI countries show smaller rural-urban gaps in service coverage than low-HDI countries. Socioeconomic inequalities are more pronounced in rural areas, particularly in services that require higher quality and adherence to standards. Socioeconomic disparities are significant in LMICs with lower HDI and are more evident in harder-to-achieve quality indicators, such as user adherence to recommended practices or treatment. For example, in medium-HDI countries, the relative inequality index (RII) for antenatal care user adherence coverage is 3.6 (95% CI=3.4-3.8) in rural areas compared with 1.9 (95% CI=1.8-2.1) in urban areas. INTERPRETATION: The research underscores the need for targeted interventions and policies to address these disparities. The evidence supports the need for a shift from focusing solely on access to care to improve the quality of care to address rural-urban and socioeconomic inequalities in RMNCH outcomes.