Smoking during pregnancy remains a major public health problem as at least 12% of pregnant women cannot quit smoking during pregnancy. This addiction is the largest preventable cause of childhood respiratory illness, including asthma, and children whose mothers smoked during pregnancy show lifetime decreases in pulmonary function. Smoking is a unique morbidity in that it is addictive, heavily advertised and recent genome studies show there are genotypes that significantly increase the likelihood of being unable to quit. Teen pregnancy, low income, low education, and living with another smoker are important factors increasing the odds of smoking during pregnancy. Pulmonary function tests done shortly after birth in babies born to mothers who smoked during pregnancy show decreased pulmonary function as measured by decreased respiratory flows and respiratory compliance and altered tidal breathing patterns. These changes can still be measured even after the infants have reached adulthood. Multiple epidemiologic studies show that these decreases in pulmonary function lead to increased respiratory disease and costs of hundreds of millions of dollars per year.
The primary aim of this double-blind, placebo controlled, randomized, multi-site study is to demonstrate improved pulmonary function testing at 3 months of age, in infants delivered to smoking mothers who are randomized to 500 mg/day of supplemental vitamin C versus placebo at less than or equal to 22 weeks of pregnancy. We will recruit 278 smoking pregnant women into the study. Patients will meet with research personnel at each prenatal visit and smoking cessation will be actively encouraged. Patients will be monitored with a set of serial biomarkers to assess smoking and medication compliance, including urine cotinine levels, smoking questionnaires, pill counts and fasting plasma ascorbic acid levels. Pulmonary function tests will be done at 3 months of age and will measure forced expiratory flows. The infants will also be followed through one year of age with monthly validated respiratory questionnaires and a follow-up pulmonary function test at 12 months of age. Success of this study is supported by strong pilot data showing statistically significant improvements at about 48 hours of age in pulmonary function tests in infants born to smoking mothers who received vitamin C versus placebo, and preliminary data showing a lower incidence of wheezing at 12 months of age in these infants. Key genetic polymorphisms shown to increase sensitivity to in-utero smoke exposure will also be measured. The success of this study is also supported by animal models showing the effectiveness of vitamin C to preserve pulmonary function and genetic and epidemiologic studies linking the effects of smoking during pregnancy to oxidant mechanisms. The secondary aims of the study include: 1) to demonstrate a decreased incidence of wheezing through 12 months of age in infants delivered to smoking mothers who are randomized to 500mg/day of supplemental vitamin C versus placebo during pregnancy; 2) to demonstrate improved pulmonary function tests at 12 months of age in these infants.
