Varenicline has not been tested in those under 18 years old or pregnant women and therefore is not recommended for use by these groups. Varenicline is considered a class C pregnancy drug, as animal studies have shown no increased risk of congenital anomalies; however, no data from human studies is available. An observational study is currently being conducted assessing for malformations related to varenicline exposure, but has no results yet. An alternate drug is preferred for smoking cessation during breastfeeding due to lack of information and based on the animal studies on nicotine.