Poor perinatal maternal mental health can negatively influence infants’ psychological wellbeing. Risk factors for poor perinatal maternal mental health are a previous mental health diagnosis; economic concerns; reduced access to perinatal services, and decreased levels of social support. The COVID-19 pandemic posed an additional stressor for perinatal women. To date, no systematic review has focused specifically on the impact of lockdowns during COVID-19 on perinatal maternal mental health. In this systematic review six electronic databases were searched for literature published between 1st January 2020 and 25th May 2021 on the impact of COVID-19 lockdowns on perinatal maternal mental health. Quantitative, peer-reviewed, cross-sectional studies published in English with perinatal women as participants, where data was collected during a period of lockdown, were included. Data was assessed for quality and narratively synthesized. Sixteen articles were included in the final review. Findings confirmed previously acknowledged risk factors for poor perinatal maternal mental health and identified additional variables which may influence perinatal maternal mental health during periods of COVID-19 lockdown. The review highlighted the potential for low-cost preventative formal interventions to support better perinatal maternal mental health. These include perinatal parent-infant art classes, talk therapy, and resilience building interventions such as ‘Wellness Recovery Action Plan’ (WRAP). Developing resources for perinatal women that integrate informal sources of support may aid them when normal routine is challenged and may mediate potential long-term impacts of poor perinatal maternal health on infants.