Background: Systematic reviews of clinical trials frequently reveal heterogeneity in the number and types of outcomes reported. To counteract this, a Core Outcome Set (COS) may be applied. Objectives: A systematic review of all completed and ongoing COS related to pregnancy and childbirth Search strategy: COMET up to January 2020, Ovid MEDLINE, EMBASE, PsycINFO, Academic Search Elite, CINAHL and SocINDEX up to June 2019. Selection criteria: Studies which prioritized outcomes using some form of consensus method (such as the Delphi technique) were included. Data collection and analysis: All included studies were checked for compliance with the Core Outcome Set–STAndards for Reporting. Information about population, setting, method and outcomes was extracted. Main results: Nineteen completed studies and thirty-nine ongoing studies were included. The number of outcomes included in various COS ranged from 6 to 48. Most COS were for conditions related to physical complications during pregnancy. No COS were identified for perinatal mental health. Conclusion: This review discloses a growing number of COS within the field of pregnancy and childbirth. Many of the completed studies follow the proposed reporting. However, several of the COS included a large number of outcomes. There is a need to consider the number of outcomes which may be included in a COS while retaining its applicability in future research. Funding This article is adapted from a report undertaken by the SBU, who provided funding for the study. Keywords: Childbirth, Core outcome set, Maternal health, Obstetric care, Pregnancy