Smoking cessation is strongly recommended during pregnancy because, in part, of its association with low infant birthweight.Studies that have compared women who do not smoke with those who continue to smoke have found that nonsmokers tend to gain more weight than smokers.Smoking during pregnancy has also been associated with increased risk of obesity in the offspring.Low income has been related to greater risk of exceeding weight gain guidelines.Finally, genetic factors may contribute to the rate of gestational weight gain.