Pregnancy and the first year after childbirth are a high-risk period of a woman's life, and research shows that women in prison are at heightened risk for poor mental health, self-harm and suicide. Whilst there has been a recent focus on studies into the health care for women in prison, research looking into the specific risk factors for poor perinatal mental health in women's prisons is sparse, with the majority having been conducted within a U.S. context that will have different provisions available and population need. This rapid evidence review explored academic literature published to identify clinical risk factors of poor perinatal mental health for women in prison in England. Following the initial search, 21 documents were identified which were then thematically analysed resulting in the identification of 72 clinical risk factors. Meta-themes identified included ‘individual’, ‘relationships’, ‘prison context’, ‘provision ’and ‘processes’. The recognition and mitigation of identified clinical risk factors is critical to ensuring quality care for women in prison and reduction of poor perinatal mental health.