Multiple micronutrient supplements (MMS) are a daily nutritional supplement of vitamins and minerals specifically formulated for pregnant women to meet the increased micronutrient requirements to support growth and development during pregnancy. Research conducted over the past two decades has provided clear and consistent evidence that MMS are safe and provide additional benefits over iron and folic acid (IFA) supplements in reducing adverse pregnancy outcomes. MMS and IFA are equally effective in preventing anemia.1–3 In 2020, the World Health Organization (WHO) released a recommendation that countries adopt MMS during pregnancy within the context of rigorous research, including implementation research (IR) that examines the acceptability, feasibility, sustainability, equity, and cost-effectiveness of MMS implementation.4 As of mid-2024, the Healthy Mothers Healthy Babies Consortium (HMHB) World Map of MMS Activities shows 23 countries and counting in different phases of MMS introduction and scale-up. The MMS in Pregnancy Technical Advisory Group (MMS TAG), hosted by the Healthy Mothers Healthy Babies (HMHB) Consortium, is supporting related efforts of its members. The MMS TAG commissioned this document to meet stakeholder demand for more guidance on the use of implementation science (IS), including rigorous IR across the phases of MMS program introduction and scale-up. This guidance document complements the Framework for Country MMS Scale-up (Framework) that was set forth by a collaboration of donors — Kirk Humanitarian, the Bill & Melinda Gates Foundation (BMGF), the Children’s Investment Fund Foundation (CIFF), and the Eleanor Crook Foundation (ECF) — in their May 2024 publication, Healthier Pregnancies and Brighter Futures for Mothers and Babies: A global investment roadmap for multiple micronutrient supplementation. The Framework presents a generalized approach to MMS program introduction that can be adapted and applied by national governments and their partners. Additionally, it identifies key results and high-level actions and activities at each phase of MMS program introduction and scale-up, and champions using IS across the process. This guidance document complements the Framework by explaining the rationale for using IS, the essential components of IS, and how IS can be applied across the pillars and phases defined in the Framework. We envision the primary audience for this guidance document to be national-level stakeholders who want to understand more specifically how IS can support efforts to introduce and scale MMS programming. These may include national or subnational MMS TAGs or task force members, government partners, implementing partners, research and academic partners, and/or private sector partners. It may be helpful to work through this guidance as a group. There is no assumption that every country starting the process and carrying out IS will ultimately decide to introduce and scale MMS programming. We believe, however, that an IS approach will contribute to improved outcomes for all maternal micronutrient supplementation interventions. – Global MMS TAG, September 2024