Vitamin C to Decrease the Effects of Smoking in Pregnancy on Infant Lung Function (VCSIP): Follow-up of a Randomized Trial

The overall aims of this protocol are to determine whether prenatal supplementation with vitamin C to pregnant smokers can improve pulmonary function and decrease wheeze at 5 years of age in their offspring. This is a continuation of the VCSIP trial, to follow the offspring through 5 years of age. The hypothesis for this protocol is an extension of the VCSIP trial that supplemental vitamin C in pregnant smokers can significantly improve their children's PFTs and decrease the incidence of wheeze. The reasons for this protocol are to follow the children born to mothers randomized in the VCSIP to the age of 5 to differentiate the patients with transient versus recurrent wheeze (and therefore more likely to develop asthma); to determine if early protective effects of vitamin C are sustained to this older age; and to continue to collect biologic samples from the children for future mechanistic studies of vitamin C action.

The primary aim of this study is to demonstrate improved pulmonary function at 5 years of age in the offspring of pregnant smokers randomized to vitamin C (500 mg/day) versus placebo. The investigators hypothesize that vitamin C supplementation in pregnancy will block the adverse effects of maternal smoking on offspring pulmonary function measured at 5 years of age by spirometry. Impulse oscillometry (IOS) will also be used at 3-5 years of age to assess pulmonary function.

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.