Weight gain associated with prenatal smoking cessation in white, non-Hispanic women

OBJECTIVE: Our purpose was to assess the effect of prenatal smoking cessation on maternal weight gain and infant birth weight in women who smoked at least five cigarettes per week. STUDY DESIGN: This prospective study followed up a sample of white, non-Hispanic pregnant smokers enrolled in three multispecialty clinics. By use of t tests, women quitting smoking before 28 weeks and continuing smokers were compared on total weight gain, Institute of Medicine weight gain categories, and infant birth weight. RESULTS: Quitters gained 36.6 pounds (SD 14.5) and smokers 28.9 pounds (SD 11.7) (p< 0.001). The relative risk of quitters gaining less than the Institute of Medicine minimum was 0.47 (95% confidence interval 0.27 to 0.81). Quitters also gained more than Institute of Medicine standards (relative risk 1.74, 95% confidence interval 1.21 to 2.51), and they were 3.1 times as likely to be delivered of infants weighing >4000 gm (95% confidence interval 1.18 to 7.97). The four low-birth-weight babies were born to smokers with low weight gain. CONCLUSION: In this population smoking cessation is associated with a lower risk of gaining too little by Institute of Medicine standards and also with higher risk of gaining more than the Institute of Medicine standard and having infants weighing >4000 gm. The clinical significance of these effects needs to be determined in further studies. (AM J OBSTET GYNECOL 1996;174:72-7.)