Taking vitamin C supplements while smoking during pregnancy was associated with a 17% improvement in forced expiratory flow (FEF) and a 40% decrease in wheezing in offspring at age 5, according to one study.
“The trajectory of airway function from early in life and continuing through adulthood may be an important risk factor for the development of chronic obstructive pulmonary disease (COPD) in adulthood,” wrote the researchers.
The results of this follow-up randomized placebo trial were published in JAMA Pediatrics.
Despite its known adverse health risks and outcomes associated with in utero smoke exposure from maternal smoking, more than 10% of US individuals continue to smoke during pregnancy, resulting in more than 400,000 infant exposures linked to an increased burden of impaired fetal lung development, decreased airway function, asthma, and wheezing.
In a previous trial conducted from 2012 to 2016, vitamin C was associated with improved pulmonary and airway function in children of pregnant smokers at age 3 months; however, the effects at age 5 had yet to be examined. This current study, conducted between 2018 to 2021, aimed to compare the effects of vitamin C, regarding airway function and occurrence of wheezing at the age of 5.
This study included a total of 251 pregnant women who smoked during their pregnancy and 213 children. Of the total of women, 125 (49.8%) were randomly selected to receive vitamin C (500mg/d) supplements, while the other 126 (50.2%) women were given a placebo.
The researcher’s primary outcome was a FEF measurement between 25% to 75% (FEF25-75) spirometry at age 5, and secondary outcomes were FEF measurements at 50% and 75% of expiration (FEF50 and FEF75), forced expiratory volume in 1 second (FEV1), and occurrence of wheezing.
Of the total of children, 192 (90.1%) had successful FEF measurements at age 5.
Additionally, 212 (99.5%) of children were included in a wheezing analysis, in which the children with mothers in the vitamin C group had 17.2% significantly higher mean measurements of FEF25-75 at 5 years (1.45 [0.04] vs. 1.24 [0.04]) L/s; adjusted mean difference (0.21; 95% CI, 0.13-0.30; P <.001).
Mean (SE) difference in the vitamin C group of offspring also increased 14.1% for FEF50 (1.50 [0.04] vs. 1.39 [0.04]) L/s; adjusted mean difference (0.20; 95% CI, 0.11-0.30; P <.001), 25.9% for FEF75 (0.79 [0.02] vs. 0.63 [0.02]) L/s; (0.16; 95% CI, 0.11-0.22; P <.001), and 4.4% for FEV1 (1.13 [0.02] vs. 1.09 [0.02]) L; (0.05; 95% CI, 0.01-0.09; P = .02).
Furthermore, children of mothers from the vitamin C group had a 40% decrease in wheezing (28.3% v 47.2%; estimated odds ratio (0.41; 95% CI, 0.23-0.74; P = .003).
Although this study had limitations given its longitudinal follow-up nature, in which cohort loss may have influenced outcomes, the researchers confirmed that there was no difference in demographics between children and pregnant smoking women in the earlier trials and this study at age 5.
The researchers believe that further studies on this cohort using spirometry and high-resolution computed tomography (HRCT) imaging may provide better insights on the effects of taking vitamin C supplements while smoking during pregnancy and how it leads to better respiratory outcomes in children and into adulthood .
“Of the phases of airway function growth into adulthood, the childhood growth phase is the least well investigated yet is potentially the most important in defining whether early life factors determine airway function trajectories, maximal airway function, and subsequent risk for COPD,” concluded the researchers.
McEvoy CT, Shorey-Kendrick LE, Milner K, et al. Effect of vitamin C supplementation for pregnant smokers on offspring airway function and wheeze at age 5 years. JAMA Pediatrics. 2023;177(1):16. doi:10.1001/jamapediatrics.2022.4401