Varenicline is a smoking cessation aid for which limited data exist concerning safety during human pregnancy. This multicentre prospective observational comparative cohort study was undertaken using surveillance data collected by the European Network of Teratology Information Services. The study sample consisted of 89 varenicline exposed pregnancies and two matched comparator groups; 267 nonteratogen exposed (NTE) controls and 78 exposed to nicotine replacement therapy or bupropion (NRT/13) for smoking cessation. For all exposed pregnancies, varenicline use only occurred in the first trimester, with a considerable proportion discontinuing use in the very early stages of pregnancy. The major congenital malformation rate (n=2/89, 2.25%) was in keeping with the expected background rate (2-4%), and was not significantly increased for first trimester varenicline-exposed infants in comparison with non-exposed controls (vs. NTE: OR 2.02, 95%CI 0.166 to 17.9, vs. NRT/B: OR 0.874, 95%CI 0.0620 to 12.3). However, the small sample size produced very imprecise risk estimates.(C) 2016 Elsevier Inc. All rights reserved.