A cross-sectional study was carried out to determine the differences in vitamin C status of Brazilian pregnant women smokers and nonsmokers and their respective newborn babies, and to assess the prevalence of hypovitaminosis C among these two groups of women. The study involved 127 pregnant women, 40 pregnant smokers and 87 pregnant nonsmokers, admitted to a maternity hospital in São Paulo, Brazil. Data concerning the pregnant women's socioeconomic, demographic, obstetric, and nutritional characteristics were collected, as well as data concerning the newborns' anthropometry and Apgar scores. A strongly significant correlation (p < 0.001) was found between the concentrations of ascorbic acid (AA) in both pregnant smokers (r = 0.77) and pregnant nonsmokers (r = 0.61) and their respective umbilical cords. The mean umbilical AA concentration was significantly higher than the mean AA concentration in pregnant women (92.05 ± 41.13 vs. 33.39 ± 18.25 mumol/L, p < 0.001). It was observed that the mean AA was significantly lower for the newborns (p = 0.03) and pregnant women (p = 0.02) from the smoking group. Forty percent (40%) of the smokers and 27% of the nonsmokers presented hypovitaminosis C. We suggest an increase in the consumption of fruits and vegetables by pregnant women, especially the smokers.