Mobile health (mHealth) has emerged as a promising avenue for extending maternal and reproductive healthcare to underserved populations in developing countries, yet adoption remains uneven and incompletely understood. This review synthesises the conceptual, technological, theoretical, and empirical literature on mHealth adoption with particular reference to maternal and reproductive health in sub-Saharan Africa and Nigeria. It clarifies the relationship between eHealth and mHealth and the electronic health literacy on which use depends; describes the principal service modalities, ranging from voice calls and short messaging to voice over internet protocol, video conferencing, and instant messaging applications; and examines two complementary frameworks, the Unified Theory of Acceptance and Use of Technology and the socio-ecological model, that together explain adoption as a product of individual, interpersonal, organisational, community, and policy level forces. The review then organises the empirical evidence on barriers and determinants into individual, household, and community categories, covering age, gender, education, marital status, religion, occupation, electronic health literacy, perceived privacy risk, household socioeconomic position and women's autonomy, place of residence, culture and ethnicity, income and poverty, and community infrastructure and cohesion. It concludes that the literature is dominated by provider-centred and developed-country studies, that holistic, multi-level analyses of patient adoption in developing settings are scarce, and that maternal and reproductive populations warrant dedicated, context-sensitive investigation grounded in both acceptance theory and socio-ecological reasoning.