User fee removal has been put forward as an approach to increasing priority health service utilization, reducing impoverishment, and ultimately reducing maternal and neonatal mortality. However, user fees are a source of facility revenue in many low-income countries, often used for purchasing drugs and supplies and paying incentives to health workers. This paper reviews evidence on the effects of user fee exemptions on maternal health service utilization, service provision, and outcomes, including both supply-side and demand-side effects. We reviewed 19 peer-reviewed research articles addressing user fee exemptions and maternal health services or outcomes published since 1990. Studies were identified through a USAID-commissioned call for evidence, key word search, and screening process. Teams of reviewers assigned criteria-based quality scores to each paper and prepared structured narrative reviews. The grade of the evidence was found to be relatively weak, mainly from short-term, non-controlled studies. The introduction of user fee exemptions appears to have resulted in increased rates of facility-based deliveries and caesarean sections in some contexts. Impacts on maternal and neonatal mortality have not been conclusively demonstrated; exemptions for delivery care may contribute to modest reductions in institutional maternal mortality but the evidence is very weak. User fee exemptions were found to have negative, neutral, or inconclusive effects on availability of inputs, provider motivation, and quality of services. The extent to which user fee revenue lost by facilities is replaced can directly affect service provision and may have unintended consequences for provider motivation. Few studies have looked at the equity effects of fee removal, despite clear evidence that fees disproportionately burden the poor. This review highlights potential and documented benefits (increased use of maternity services) as well as risks (decreased provider motivation and quality) of user fee exemption policies for maternal health services. Governments should link user fee exemption policies with the replacement of lost revenue for facilities as well as broader health system improvements, including facility upgrades, ensured supply of needed inputs, and improved human resources for health. Removing user fees may increase uptake but will not reduce mortality proportionally if the quality of facility-based care is poor. More rigorous evaluations of both demand- and supply-side effects of mature fee exemption programmes are needed.