Data are limited on hereditary angioedema (HAE) in pregnant women and the safety and efficacy of therapies for treatment and prevention of HAE attacks during pregnancy. Prospective studies are unlikely given the rarity of HAE and ethical considerations regarding enrollment of pregnant female subjects in clinical trials. A retrospective analysis of clinical trial and compassionate-use data was conducted to identify subjects who received nanofiltered C1 esterase inhibitor (C1 INH-nf; human) during pregnancy. This study evaluates the efficacy and safety of human C1 INH-nf for treatment and prevention of HAE attacks in pregnant women. Data from pregnant subjects enrolled in either open-label extensions of two randomized, double-blind, placebo-controlled trials of C1 INH-nf or in a compassionate-use program were retrospectively analyzed for efficacy (e.g., total attacks, attack frequency during prophylaxis, and monthly attack rates) and safety (e.g., pregnancy outcomes and adverse events). C1 INH-nf was administered as acute treatment, preprocedural prophylaxis, or routine prophylaxis. C1 INH-nf prophylaxis substantially reduced monthly attack rates. Of 16 subjects, 13 delivered 14 healthy neonates (1 set of twins). Two adverse fetal outcomes were reported; neither was considered by the principal investigator to be related to C1 INH-nf. One subject’s pregnancy outcome was unknown. This analysis shows a favorable risk-benefit profile for C1 INH-nf for managing HAE during pregnancy. NCT Identifier: NCT00438815; NCT00462709.