Background:
     
     Hypertensive disorders account for 14% of global maternal deaths. Magnesium sulphate (MgSO₄ ) is recommended for prevention and treatment of pre-eclampsia/eclampsia. However, MgSO₄ remains underused, particularly in low- and middle-income countries (LMICs).
   

Objective:
     
     This qualitative evidence synthesis explores perceptions and experiences of healthcare providers, administrators and policy-makers regarding factors affecting use of MgSO₄ to prevent or treat pre-eclampsia/eclampsia.
   

Search strategy:
     
     We searched MEDLINE, EMBASE, Emcare, CINAHL, Global Health and Global Index Medicus, and grey literature for studies published between January 1995 and June 2021.
   

Selection criteria:
     
     Primary qualitative and mixed-methods studies on factors affecting use of MgSO₄ in healthcare settings, from the perspectives of healthcare providers, administrators and policy-makers, were eligible for inclusion.
   

Data collection and analysis:
     
     We applied a thematic synthesis approach to analysis, using COM-B behaviour change theory to map factors affecting appropriate use of MgSO₄ .
   

Main results:
     
     We included 22 studies, predominantly from LMICs. Key themes included provider competence and confidence administering MgSO₄ (attitudes and beliefs, complexities of administering, knowledge and experience), capability of health systems to ensure MgSO₄ availability at point of use (availability, resourcing and pathways to care) and knowledge translation (dissemination of research and recommendations). Within each COM-B domain, we mapped facilitators and barriers to physical and psychological capability, physical and social opportunity, and how the interplay between these domains influences motivation.
   

Conclusions:
     
     These findings can inform policy and guideline development and improve implementation of MgSO₄ in clinical care. Such action is needed to ensure this life-saving treatment is widely available and appropriately used.
   

Tweetable abstract:
     
     Global qualitative review identifies factors affecting underutilisation of MgSO₄ for pre-eclampsia and eclampsia.