Background: Post-traumatic stress disorder (PTSD) affects approximately 3% of women in the postnatal period, but less is known about risk factors for PTSD than for other postnatal mental illnesses. Objectives: To analyse literature surrounding the impact of mode of birth on postnatal PTSD. Search Strategy: Five databases were systematically searched (1990-2019). Selection Criteria: Studies investigating the link between mode of birth and postnatal PTSD in high income countries. Data Collection and Analysis: Quantitative and qualitative data were collected and synthesised. Meta-analysis was performed with four of the studies, and the rest were analysed narratively. Main Results: Twelve quantitative and two qualitative studies were included in the review. Most found a significant relationship between mode of birth and maternal PTSD symptoms. Meta-analysis found caesarean section was more associated with PTSD than vaginal delivery (VD) (p=0.005), emergency caesarean section (EmCS) more than elective caesarean section (ElCS) (p<0.001), instrumental vaginal delivery (IVD) more than spontaneous vaginal delivery (SVD) (p<0.001) and EmCS more than VD (P<0.001). Women who developed PTSD after EmCS felt less in control and less supported than those who did not develop it after the same procedure. Request for repeat ElCS appeared more common among women with pre-existing postnatal PTSD, but this may subsequently leave them feeling dissatisfied and their fears of childbirth unresolved. Conclusions: Modes of birth involving emergency intervention may be risk factors for the development of postnatal PTSD. Ensuring that women feel supported and in control during emergency obstetric interventions may mediate against this risk.