Background. Approximately 1–2% of women suffer from post-traumatic stress disorder (PTSD) postnatally. This review aims to elucidate how women at risk can be identified. Methods. A systematic search of the published literature was carried out using the MEDLINE database (November 2003 to 29 October 2010) with both MeSH terms and free text. Thirty-one studies were considered appropriate for qualitative synthesis. Articles were included on the basis of (a) publication pertaining to PTSD following childbirth, (b) study carried out in Western Europe and (c) publication written in English. The results were primarily based on observational studies. The literature was thoroughly read and results were compiled. Furthermore, a novel quality rating system was employed to minimize the impact of bias. Results. Subjective distress in labor and obstetrical emergencies were the most important risk factors. Infant complications, low support during labor and delivery, psychological difficulties in pregnancy, previous traumatic experiences, and obstetrical emergencies were identified as risk factors. Conclusions. We have identified factors both strongly associated and non-associated with PTSD following childbirth. While the literature is limited by methodological shortcomings, a hypothesis regarding the development of PTSD is outlined, and recommendations with respect to screening and future research are provided.