High-quality antenatal care (ANC) helps reduce the global burden of maternal and perinatal mortality and morbidity. In Nepal and India, despite progress in ANC coverage, substantial gaps in quality of care remain. Electronic decision support systems (EDSS) have been implemented in many settings with the aim of improving adherence to clinical guidelines, but evidence of their effectiveness remains mixed, and implementation is often challenging. This mixed-method PhD examined the implementation and consequences of an EDSS that aimed to improve ANC quality in Nepal and India. Data were drawn from the mIRA project and the development and evaluation of a complex EDSS intervention in rural primary care facilities in Bagmati Province, Nepal and Telangana, India. Multiple quantitative data sources were used to describe ANC coverage and quality in India as part of the project’s formative phase. Using mixed-method, realist-informed approaches, I examined how EDSS implementation unfolded in Nepal and the effects on healthcare providers’ workload in ANC. ANC quality in the study setting in India identified gaps in some risk screening processes that the mIRA project sought to address, as wells as gaps in counselling and responsive, person-centred care. The EDSS intervention was conceptualised as operating largely through reminders, and the process evaluation focused on documentation and understanding the process of implementation. Fidelity to point-of-care use, which was critical for the reminder function, declined over time as healthcare providers overwhelmingly viewed the intervention as for record keeping rather than decision support. The intervention did not substantially change workload, or healthcare provider performance, in ANC. The thesis highlights the complexity of improving ANC quality and the mismatch between the potential of an EDSS intervention and how it was used (or not used) in practice, offering an approach for how an EDSS intervention for ANC can be evaluated and its results understood.