The impact of tobacco smoking on perinatal outcome among patients with gestational diabetes.

OBJECTIVE: To determine the effects of tobacco use on perinatal outcomes among patients with gestational diabetes (GDM).

STUDY DESIGN: This was a retrospective cohort study of singleton pregnancies with GDM and live births from 2003 to 2006. The primary outcome, large for gestational age (LGA) infants, was compared between smoking and nonsmoking groups. Secondary outcomes included cesarean deliveries, shoulder dystocia, birth trauma, peripartum complications, macrosomia, 5-min Apgar score < or =3, birth defects, and neonatal intensive care unit (NICU) admissions. chi(2) and Student t-tests compared the two groups; a P-value <0.05 was statistically significant and odds ratios (OR) were reported with 95% confidence intervals (CI). A multivariate logistic regression analysis controlled for variables known to affect outcomes in GDM.

RESULT: We identified 915 patients with GDM, of which 130 (14.2%) smoked during pregnancy. Women who smoked during pregnancy were less likely to have LGA infants (22.4 vs 31.2%; OR, 0.61; 95% CI, 0.39 to 0.95). In a logistic regression analysis, the inverse relationship between smoking and LGA persisted (OR, 0.59; 95% CI, 0.36 to 0.97) after controlling for maternal age, multiparity, ethnicity, weight status before pregnancy, weight gain during pregnancy, and male gender. Preterm labor, preeclampsia, Cesareans, shoulder dystocia, and birth trauma were similar in both groups. PPROM was more likely to occur in nonsmokers (0 vs 4%, P=0.03), but postpartum hemorrhage was more common among smokers (OR, 2.3; 95% CI, 1.02 to 5.31). Macrosomia, low 5-min Apgar score, birth defects, and NICU admissions were similar between the groups.

CONCLUSION: Patients with GDM who smoke during pregnancy were 40% less likely to have LGA infants. However, smoking was not protective of other common morbidities associated with GDM.