How vitamin C intake in pregnant smokers affects the trajectory of airway function in their offspring | Image credit: © mitarart – © mitarart – Stock.adobe.com.
Investigators in recent research letters published in JAMA Pediatrics To better understand how vitamin C supplementation of pregnant smokers affects the trajectory of airway function in their offspring, we highlighted a secondary analysis of a randomized clinical trial.1
The original study, the Vitamin C to Reduce the Effects of Smoking During Pregnancy on Infant Lung Function (VCISP) trial, found that supplementing women who smoked during pregnancy with vitamin C at 3 and 12 months of age The child’s forced expiratory flow (FEF) increased “significantly.” of age.1
The study was randomized, double-blind, and placebo-controlled and was conducted at three centers in 251 pregnant smokers who were randomized between 13 and 23 weeks of gestation. Of these participants, 125 were randomized to vitamin C (500 mg/day) and 126 to placebo.2, 3
The primary endpoint was FEF75 (measurement of FEF at 75% of exhaled volume) after 3 months. Although this result was not met, the secondary outcomes FEF50 and FEF25-75 were significantly improved at 3 and 12 months of age.2, 3
Through a 60-month long-term follow-up study, the researchers demonstrated that the offspring continued to have significantly higher FEF25-75 and significantly less wheezing.1
To assess the association between FEF25-75 and the occurrence of wheeze between ages 4 and 6 years, the study authors evaluated the FEF25-75 obtained in female offspring at 3, 12, and 60 months of age. conducted a new longitudinal analysis of In the VCSIP trial and new mediation analysis, smoking during pregnancy.1
FEF was measured using spirometry at 3, 12, and 60 months of age, and wheezing was measured by quarterly standardized respiratory questionnaires. Long-term treatment differences in FEF25-75 were assessed by general linear mixed models, repeated measures of covariance.1
Results show that 243 offspring were born, 233 had 1 of 3 FEF measurements, and 80% had data at 60 months and 80% had data at 3 or 12 months. I had.1
Longitudinal analysis of FEF25-75 showed significantly higher values in the offspring of the vitamin C group (P < .001), and FEF increases by 25% to 75% with increasing age,” the researchers said. 1 The incidence of wheezing was significantly lower in the vitamin C group (30 vs. 50) [28.3% vs 47.2%]odds ratio: 0.41, 95% CI, 0.23-0.74 [P = .003]).1
Additionally, mediation analysis revealed that most of the association between vitamin C and wheezing was mediated through the association between increased FEF25-75 and vitamin C (total percentage, 54.2%) . [P = .03]).1
A secondary analysis revealed that supplementing women who smoked during pregnancy with vitamin C increased their offspring’s FEF25-75 trajectory by age 5. The difference in FEF25-75 between treatment groups increased with age, despite not receiving postnatal supplementation, the researchers wrote.1
In addition, the vitamin C group had less incidence of wheezing at ages 4 to 6 years.
“Our findings provide evidence that there is a direct association between maternal smoking during pregnancy and the occurrence of wheezing in children,” the authors concluded.
This article was originally published by our sister publication Contemporary Pediatrics.
References:
1. McEvoy CT, Shorey-Kendrick LE, MacDonald KD, et al. Vitamin C supplementation in pregnant smokers and the trajectory of offspring airway function: a secondary analysis of a randomized clinical trial. JAMA Pediatrics. Published online on April 8, 2024. doi:10.1001/jamapediatrics.2024.0430
2. McEvoy CT, Shorey-Kendrick LE, Milner K, et al. Oral vitamin C (500 mg/day) to smokers during pregnancy improves airway function in infants at 3 months of age (VCSIP). Randomized trial. Am J Respir Crit Care Med. 2019;199(9):1139-1147. doi:10.1164/rccm.201805-1011OC
3. McEvoy CT, Shorey-Kendrick LE, Milner K, et al. Vitamin C administration to pregnant smokers results in sustained improvements in airway function in infants up to 12 months of age: a randomized trial. European Respiratory Journal. December 2020, 56(6)1902208; DOI: 10.1183/13993003.02208-2019
