Originally published by 2 Minute Medicine^® (view original article). Reused on AccessMedicine with permission.

1. In this multi-center randomized controlled trial, vitamin C supplementation in pregnant smokers was associated with better lung function in offspring at the age of five.

2. Additionally, vitamin C supplementation in pregnant smokers was also associated with decreased occurrence of wheezing in offspring.

Evidence Rating Level: 1 (Excellent)

Exposure to cigarette smoking in utero is a risk factor for impaired fetal lung development, decreased airway function, and development of asthma in the offspring. Supplementation of vitamin C for pregnant smokers has been shown to increase offspring airway function until the age of 12 months. However, the long-term effects of vitamin C supplementation during pregnancy on airway function have not been assessed.

This multi-center randomized control trial conducted in the United States included 251 pregnant patients aged 15 years or older. Participants were current smokers, defined as having smoked ≥1 cigarette in the last week, and were between 13- and 22-weeks’ gestation. Patients were excluded if they had complex medical conditions, were currently incarcerated, or had unstable methods of communication. 125 patients were randomized to receive vitamin C (500mg/d) and 126 received placebo. The primary outcome was forced mid-expiratory flow (FEF_25-75) measured by spirometry at age five. Secondary outcomes included forced expiratory volume in 1 second (FEV₁) and self-reported or clinically recorded occurrence of wheeze between 4 and 6 years old.

Results demonstrated that at five years old, children of pregnant smokers who received vitamin C had improved airway function, demonstrated by improvements in FEF_25-75 and significantly decreased occurrence of wheeze, compared to the placebo group. This study is limited by potential misclassification of wheeze, which was assessed using survey responses from a parent or caretaker. However, the observed clinically important improvements and lack of adverse events associated with vitamin C supplementation after a long follow-up period are high encouraging for the use of vitamin supplementation in pregnant smokers. Further trials to determine the optimal regimen and time of supplementation during initiation is still needed.

Click to read the study in JAMA Pediatrics

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