Recent research has shed light on the potential connection between vitamin C supplementation during pregnancy and wheezing in children, particularly those whose mothers smoked during pregnancy. A secondary analysis of clinical trial data indicated that improved airway function may mediate this association. Longitudinal analyses revealed that children whose mothers took vitamin C showed significantly higher forced expiratory flow between 25% and 75% expired volume (FEF25%-75%) values at ages 3, 12, and 60 months compared to children of mothers who received a placebo. This increase in FEF25%-75% persisted as the children aged, even without postnatal supplementation.
Reduction in Wheeze Occurrence
One of the key findings of the study was a significant decrease in wheezing among children in the vitamin C group between the ages of 4 and 6 years. The odds of experiencing wheezing were lower in this group compared to the placebo group (OR 0.41, 95% CI 0.23-0.74, P=0.003). Interestingly, a substantial portion (54.2%) of the association between vitamin C and wheezing appeared to be mediated through the improved airway function indicated by FEF25%-75%.
The researchers highlighted the direct association between maternal smoking during pregnancy and the occurrence of wheezing in offspring. Smoke exposure in utero is known to be a risk factor for respiratory issues later in life, emphasizing the importance of understanding the factors that can mitigate these risks. While the percentage of mothers who smoke during pregnancy has decreased over time in the U.S., it remains a significant concern, with implications for childhood respiratory health.
The study analyzed data from the Vitamin C to Decrease Effects of Smoking in Pregnancy on Infant Lung Function (VCSIP) trial, where women who smoked during pregnancy were randomized to receive either 500 mg/day of vitamin C or placebo. Follow-up assessments showed improved airway flow and reduced wheezing in children up to age 5 whose mothers took vitamin C during pregnancy. Spirometry FEF measurements were taken at ages 3, 12, and 60 months, while wheezing was assessed through standardized respiratory questionnaires.
The study included a total of 243 offspring, with most receiving at least one FEF measurement. The population consisted of nearly equal numbers of male and female children, with the majority being white. At each age assessed, there were no significant differences in demographic factors such as sex, race, or postnatal smoke exposure between the vitamin C and placebo groups. This homogeneity in participant characteristics strengthens the internal validity of the findings.
The researchers acknowledged that wheezing in pediatric patients can be challenging to detect, which may have influenced the results. Future studies could benefit from more comprehensive assessments of respiratory outcomes and potentially explore additional factors that could influence the relationship between maternal vitamin C supplementation and childhood wheezing. Overall, the study provides valuable insights into the potential benefits of vitamin C during pregnancy in mitigating the risk of respiratory issues in children exposed to maternal smoking.
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