A total of 52 female Wistar rats were distributed into four groups: non-diabetic (G1) and diabetic (G2) exposed to filtered air; non-diabetic (G3) and diabetic (G4) exposed to cigarette smoke. Diabetes was induced by streptozotocin (40 mg/kg bodyweight, i.v.). Rats were exposed, for 30 min, to filtered air (control) or to tobacco smoke generated from 10 cigarettes, twice a day, for 2 months. At the end of the 2-month exposure, at day 21 of pregnancy, each rat was anesthetized and humanely killed for laparotomy. Uterine horns were exposed for reproductive performance analysis, fetal and placental weights and placental index. Maternal and fetal data were analysed by ANOVA followed by the Student Newman-Keuls test. Fetal weight classification was assessed by Fisher's exact test. Diabetes and cigarette smoke caused placentomegaly (G4 = 0.65 +/- 0.19 g versus G1 = 0.49 +/- 0.03 g, P < 0.05), increased placental index (G4 = 0.13 +/- 0.03 versus G1 = 0.09 +/- 0.00, P < 0.05) and small fetus rates for pregnancy age (G4 = 88% versus G1 = 23.2%, P < 0.05). These observations show the importance of encouraging pregnant women to attempt cessation of smoking.