Smoking during pregnancy increases the risks of maternal and fetal complications and adverse neonatal outcomes, and it remains a significant health problem. Although pregnancy is often a strong motivator for smoking cessation, many pregnant women continue to smoke. Effective smoking cessation strategies for use during pregnancy are therefore clearly needed. Behavioural support provided by prenatal smoking cessation programs is safe and effective during pregnancy, but it generates a relatively modest reduction in smoking cessation rates. Nicotine replacement therapy (NRT), in conjunction with behavioural support, may offer an effective alternative to help pregnant women quit smoking. This suggestion is based on the convincing research evidence for the effectiveness of NRT in the general population. There is no consensus, however, on whether or not care providers should recommend NRT during pregnancy because of persistent concerns about its safety and effectiveness. We reviewed the data on the safety and effectiveness of NRT and on the possible physiological reasons for NRT's low effectiveness in pregnant women, and conclude that it is prudent to advise pregnant women who smoke 5 cigarettes or fewer per day to use behavioural support, and not NRT, to help them quit. Pregnant women with a moderate or high level of addiction may use NRT under the supervision of their physician. A combination of cognitive-behavioural therapy and counselling with NRT is the most effective strategy to achieve smoking cessation during pregnancy.