In France, approximately 500 deaths per year are related to sudden infant death syndrome (SIDS). After a 75% reduction of SIDS-related deaths in the 1990s, thanks to large prevention campaigns directing parents to put their infants to sleep on their back, the number of SIDS-related deaths remains stable. However, we estimate that 100–200 infant deaths per year in France could be prevented with better education on the risk factors for SIDS. In this prospective, descriptive monocentric study, we aimed to evaluate the level of expectant women's knowledge about SIDS. Questionnaires were distributed during a midwife consultation. A score on sleeping conditions, environmental and protective factors was determined with coefficients attributed according to their relevance to SIDS. Of 296 questionnaires distributed, 202 were completed and included in the analysis from March 1 to September 21, 2018. Scores were distributed from 2 to 46/50. The average score was 28.6/50. Information was principally obtained from media and not health professionals. When the information was delivered by a caregiver, in particular by a paediatrician, we observed better knowledge among these women. This study shows that it is important for health professionals to take the time to inform future mothers about the risk factors for SIDS, especially the least informed population groups such as young mothers and those from lower socioeconomic status, in order to reduce the number of avoidable infant deaths.