BACKGROUND: The birth plan was introduced in the 1980s to facilitate communication between maternity care providers and women and increase agency for childbearing women in the face of medicalised birth. Forty years on, the birth plan is a heterogeneous document with uncertainty surrounding its purpose, process, and impact. The aim of this review was to synthesise the evidence and improve understanding of the purpose, process and impact of the birth plan on childbearing women's experiences and outcomes. METHODS: This systematic review followed the PRISMA guidelines. A comprehensive search strategy was designed and applied to electronic databases CINAHL, MEDLINE, PsychINFO, Cochrane Library, Scopus, and ClinicalTrials.gov. Articles were appraised using the Crowe Critical Appraisal Tool and a five-step integrative approach to analysis followed. FINDINGS: Eleven articles were identified, all quantitative in nature. It is clear that the general purpose of birth plans is communication, with decision making a key factor. Even though the processes of birth planning were varied, having a birth plan was associated with generally positive birth outcomes. CONCLUSIONS: Despite the heterogeneity of birth plans, birth plans were associated with positive outcomes for childbearing women when developed in collaboration with care providers. The act of collaboratively creating a birth plan may improve obstetric outcomes, aid realistic expectations, and improve satisfaction and the sense of control.