Severe factor XI deficiency is an injury-related bleeding disorder. The risk of excessive post-partum hemorrhage in affected women has so far been evaluated in a relatively small number of patients and it is uncertain whether prophylactic treatment with fresh frozen plasma or factor XI concentrate is needed during or after vaginal or cesarean delivery. We retrospectively analyzed bleeding manifestations related to vaginal and/or cesarean deliveries in a cohort of 62 women with factor XI activity < 17 U/dl and evaluated whether replacement therapy is essential. Fifty-one women had 139 vaginal deliveries, six women had 13 cesarean deliveries, and five women had seven vaginal as well as five cesarean deliveries. Forty-three of the 62 women (69.4%) never experienced post-partum hemorrhage during 93 deliveries (85 vaginal, eight cesarean). Hemorrhage occurred in 19 women, which in six women accompanied each one of their 17 vaginal deliveries. Post-partum hemorrhage had no relationship with the abnormal genotype that caused factor XI deficiency nor with factor XI level. These observations suggest that the use of fresh frozen plasma or factor XI concentrate during and/or after vaginal delivery is not mandatory in women with severe factor XI deficiency and can be reserved for patients who develop excessive hemorrhage. For women requiring cesarean section it appears that the same policy can be advocated but more observations are needed.