Table 1.

Definitions of realist concepts.

Concept	Definition/description
Intervention (I)	Refers to the features and characteristics of the various mHealth interventions such as type of technology, cointerventions, and mode of delivery.
Context (C)	Refers to “… features of the conditions in which programmes are introduced, that are relevant to the operation [of] the programme mechanisms”40 p. 7, and answers the question: in what circumstances will a program work?We differentiate two layers of context:ii) Environmental (C1): the broad external environment in which interventions are situated, following a PESTELI typology, i.e. political, economic, social, technological, environmental, legal, and infrastructural.iii) Organizational/Health System (C2): resources, policies, and structures directly related to the unique health facility settings in which mobile technology is introduced.
Actors (A):	This describes the individual users of mHealth—in this case, health workers of varying cadres and levels of experience and skills, who are expected to use mHealth for maternal health service delivery.
Mechanism (M)	Mechanisms are behavioral, cognitive, affective, and social responses to mHealth which can explain the (un)intended outcomes of its use.41They refer to the ways in which the resources offered through mHealth in a given context may permeate into the reasoning of the actors, leading to various outcomes.40,42
Outcome (O)	Outcomes include changes due to mHealth interventions and their intended or unintended consequences.Although the review started off with a focus on health worker performance as an outcome of mHealth use, further on we explain the rationale behind expanding the scope of the review to explore more proximal outcomes.

mHealth: Mobile health.