Background A substantial proportion of maternal and neonatal mortality and morbidity is attributable to gaps in quality of care. A systematic, standard-based tool for quality assessment and improvement for maternal and neonatal hospital care (QA/QI MN tool) was developed in 2009 by the World Health Organization (WHO). The tool guides the assessment process along the whole continuum from admission to discharge, collects the views of the recipients of care and engages hospital mangers and staff in identifying gaps and drafting an action plan. Methods Publications describing use of the WHO QA/QI MN tool from 2009 to 2017 and reports retrievable from WHO or other development partners’ websites were searched and considered for inclusion in the review. Only assessments of hospitals were considered. Quality gaps were classified as regarding case management in maternal care, case management in neonatal care, hospital infrastructure, hospital policies and according to severity and frequency. Quotations from women regarding key issues in effective communication, respect and dignity, emotional support and costs incurred were selected. Results In the period 2009-2017, use of the WHO QA/QI MN tool was documented in 25 countries, belonging to Central and Eastern Europe (8), Central Asia (4), Sub-Saharan Africa (11), Latin America (1) and Middle East (1). Overall, 133 hospitals were assessed. The tool allowed to identify in great detail serious quality gaps including: insufficient or incomplete adherence to recommended evidence-based procedures for normal childbirth and maternal and neonatal complications; excess of inappropriate or unnecessary interventions; insufficient infection control; failure to provide respectful care, adequate communication and emotional support to mothers and babies; poor use of information generated locally to analyse processes and outcomes. These gaps were observed in all countries. Significant differences were observed among facilities belonging to the same health systems, ie, with very similar staffing, infrastructure and equipment. Conclusions The experience made, the largest of this kind, provides comprehensive and detailed insight into the existing quality gaps in a wide variety of settings. QI cycles at facility level should be primarily based on assessments made by multidisciplinary teams of professionals to identify the parts of the care pathways which require improvement through a participatory approach involving managers, staff and patients.