Vitamin C, smoking cessation during pregnancy may improve infant airway function

Vitamin C supplementation, in conjunction with smoking cessation counseling, significantly increased airway function through 12 months of age among the offspring of pregnant smokers, researchers reported in the European Respiratory Journal.

“While smoking cessation in pregnancy remains the No. 1 priority and vitamin C supplementation does not justify continued smoking, in reality, 50% of pregnant smokers continue to smoke despite viraginous antismoking campaigns,” Cindy T. McEvoy, MD, MCR, professor in the department of pediatrics and director of child health research in pediatrics at the School of Medicine at Oregon Health and Science University, Portland, and colleagues wrote. “This study demonstrates that the safe, inexpensive and simple intervention of vitamin C supplementation can persistently improve the airway function of infants exposed to in utero smoke.”

The randomized, double-blind, placebo-controlled trial enrolled 251 pregnant women who reported smoking at 12 to 23 weeks of gestation. Participants were randomly assigned to receive 500 mg daily vitamin C supplementation (n = 125) or placebo (n = 126). Researchers provided smoking cessation counseling to all participants.

Researchers performed forced expiratory flow in 222 infants at age 3 months and in 202 infants at age 12 months.

Infants of mothers who were assigned vitamin C supplementation demonstrated significantly increased forced expiratory flow during the first year of life compared with infants of mothers assigned placebo. Overall increased flow was 40.2 mL per second for forced expiratory flow at 75% FVC (P = .025), 58.3 mL per second for forced expiratory flow at 50% FVC (P = .0081) and 55.1 per second for forced expiratory flow at 25% to 75% FVC (P = .013).

“The results of this study, as well as our previous clinical trial in newborns, cumulatively demonstrate that vitamin C improves lung function at birth and these improvements are maintained throughout the first year of life,” the researchers wrote.

The researchers cited several limitations of this study, including that the study was underpowered for wheeze, its short 12-month follow-up and vitamin C supplementation was not continued postnatally, which may have provided additional protection for offspring’s airways exposed to postnatal smoking.

The offspring in this study will be followed through age 5 years.