Vitamin C supplementation in pregnant smokers boosts offspring’s respiratory health

Supplementation with vitamin C in pregnant women appears to minimize the effects of smoking on childhood respiratory health, with a recent study showing that it is associated with increased airway function and lower occurrence of wheeze among children born to mothers who smoked during pregnancy.

Researchers followed 251 participants from the Vitamin C to Decrease the Effects of Smoking in Pregnancy on Infant Lung Function (VCSIP), a double-blinded randomized clinical trial that assigned pregnant smokers to receive vitamin C (500 mg/d; n=125) or placebo (n=126) treatment. The children of the participants completed forced expiratory flow (FEF) measurements by spirometry at 5 years of age.

The primary endpoint was the prespecified FEF measurement between 25% and 75% expired volume (FEF25-75) at age 5 years. Secondary endpoints were FEF measurements at 50% and 75% of expiration (FEF50 and FEF75), forced expiratory volume in 1 second (FEV1), and wheeze.

Of the 213 children from the VCSIP trial who were included in this follow-up study, 192 (90.1 percent) had successful FEF measurements at age 5 years and 212 (99.5 percent) were included in the analysis of wheeze.

The mean FEF25-75 at age 5 years was 17.2 percent higher among children born to pregnant smokers who had received vitamin C vs placebo (1.45 vs 1.24 L/s; adjusted mean difference, 0.21, 95 percent confidence interval [CI], 0.13–0.30; p<0.001).

Furthermore, the mean FEF50 was higher by 14.1 percent (1.59 vs 1.39 L/s; adjusted mean difference, 0.20, 95 percent CI, 0.11–0.30; p<0.001), the mean FEF75 was higher by 25.9 percent (0.79 vs 0.63 L/s; adjusted mean difference, 0.16, 95 percent CI, 0.11–0.22; p<0.001), and FEV1 was higher by 4.4 percent (1.13 vs 1.09 L; adjusted mean difference, 0.05, 95 percent CI, 0.01–0.09; p=0.02).

Finally, significantly fewer children of pregnant smokers randomized to vitamin C developed wheeze (28.3 percent vs 47.2 percent; odds ratio, 0.41, 95 percent CI, 0.23–0.74; p=0.003).