Background and Objective: There is little information on pregnancy and delivery in patients with hereditary angioedema due to C1 inhibitor deficiency (C1INH-HAE). The aim of this study was to describe the effect of pregnancy and deliveries on symptoms of C1INH-HAE and review the need for and safety of treatments available during the study period. Methods: Retrospective review using a purpose-designed questionnaire of 61 C1INH-HAE patients from 5 hospitals specialized in the management of HAE in Spain. The outcomes measured were number of pregnancies, changes in symptoms during pregnancy and delivery, mode of delivery, type of anesthesia during delivery, treatments received, and tolerance of treatments. Results: We reviewed 125 full-term pregnancies (89 without a prior diagnosis of C1INH-HAE), 14 miscarriages, and 4 induced abortions. Patients reported an increased frequency of C1INH-HAE symptoms in 59.2% of pregnancies (74/125) and the presence of symptoms throughout pregnancy in 40% (50/125). Prophylactic C1INH-HAE therapy was used during 9 (7.2%) of the 125 pregnancies. Nine patients-in 11 pregnancies (8.8 %)-received treatment for acute attacks. Most deliveries (n=110, 88%) were vaginal. A cesarean section was necessary in 15 cases (12%). Short-term prophylaxis with pdhC1INH was administered before 14 deliveries (11.2 %); 111 deliveries (88.8 %) were performed without premedication and were well tolerated. Anesthesia was used in 51 deliveries (40.8%). Conclusions: Pregnancy has a variable influence on the clinical expression of C1INH-HAE. Attacks tend to occur more frequently but not to increase in severity. Vaginal delivery was mostly well tolerated. pdhC1INH prophylaxis should be administered prior to cesarean delivery and is also recommended before vaginal delivery if there are additional risk factors. pdhC1INH should always be available in the delivery room.