Specific Aim 2 (Secondary Outcome): The secondary aim of this study is to demonstrate a decreased incidence of wheeze at 5 years of age in offspring of pregnant smokers randomized to vitamin C (500 mg/day) versus placebo. The investigators hypothesize that vitamin C supplementation during pregnancy will decrease the incidence of wheeze at 5 years of age in offspring of smokers. Respiratory health will be assessed by quarterly validated respiratory questionnaires and clinician report.