Introduction - A pertussis outbreak in a maternity ward raised concerns about the risk of infection among newborns. This report describes the strategy and measures implemented to prevent such transmission at a maternity ward in the Yvelines department in June 2006. Methods - Following the establishment of a crisis response team in coordination with the French Institute for Public Health Surveillance, the strategy adopted included screening for secondary cases; identification of at-risk patients; providing information and establishing a hotline for exposed patients; organizing staff information sessions; case-by-case prophylaxis for coworkers in close contact with confirmed cases; and, most importantly, the immediate implementation of vaccination for staff in the maternity and neonatal units. Results - The outbreak lasted three months, during which 10 cases were identified among staff. Of the 664 patients and 109 newborns exposed, 151 (96 newborns and 55 patients) received prophylactic treatment. Only one patient developed pertussis, but no newborns did. The cost to the facility is estimated at 50,000 euros. Conclusion - During an outbreak capable of causing serious consequences in newborns, the responsiveness and coordination of the various stakeholders, communication among professionals, and information provided to patients and staff are essential. (R.A.)