Vitamin C improves lung function in babies exposed to in-utero smoke
Vitamin C supplementation in pregnant women who smoke resulted in improved forced expiratory flow (FEF*) in their newborns at 3 and 12 months, according to data presented at ATS 2018.
“[Our findings are of] great public health significance to potentially alter the foetal origins of respiratory disease,” said Dr Cynthia McEvoy from the Oregon Health & Science University School of Medicine in Portland, Oregon, US. “We used FEFs … [as they] provide a more direct measurement of actual airway function, and are more predictive of future disease.”
A total of 252 pregnant women (<23 weeks, singleton gestation) who were current cigarette smokers were randomized 1:1 to receive vitamin C (500 mg) daily or placebo through delivery. A total of 243 infants were delivered (n=120 and 123 in the vitamin C and placebo groups, respectively). Median cigarette use was 7 cigarettes/day. [ATS 2018, abstract A4192]
Ascorbic acid levels were higher in the vitamin C group vs the placebo group (60.8 vs 41.6 µmol/L for mid-gestation and 54.6 vs 39.6 µmol/L for late gestation; p<0.05 for both).
At 3 months, significant difference in lung function was observed at two intervals between offspring born to women in the vitamin C and placebo groups (436.7 vs 408.5 mL/sec; p=0.02 and 387.4 vs 365.8 mL/sec; p=0.04 for FEF50** and FEF25-75, respectively).
The improvement in lung function persisted through 12 months at all intervals (351.6 vs 324.0 mL/sec; p=0.03, 654.5 vs 616.1 mL/sec; p=0.05, and 609.0 vs 567.1 mL/sec; p=0.02 for FEF75, FEF50, and FEF25-75, respectively).
After adjusting for gestational age and other covariates, FEF75 at 3 and 12 months demonstrated a significant effect with vitamin C vs placebo (p=0.002).
The current results supplement the initial findings showing improved pulmonary function tests and reduced incidence of wheeze through 1 year with vitamin C supplementation. [JAMA 2014;311:2074-2081]
Despite active antismoking campaigns and information about nicotine’s addictive nature, about 10–12 percent of American women cannot quit smoking while pregnant, McEvoy pointed out. Maternal smoking during pregnancy adversely affects foetal lung development, which could lead to lifelong reduced pulmonary function and increased asthma risk in the offspring, she added.
Vitamin C supplementation in this population may improve pulmonary function trajectory of the offspring by blocking some of the effects of in-utero smoke/nicotine on lung structure and function, she said. [Am J Respir Crit Care Med 2005;171:1032-1039]
A potential mechanism that could elucidate the improved lung function is the interaction between nicotine and nicotinic receptors in developing lungs, noted McEvoy. “[This] may be a key mediator of the effects of maternal smoking on lung development … [and generate] increased reactive oxygen species. Somehow, vitamin C is blocking that.”
For women who cannot quit smoking during pregnancy, these findings show that vitamin C supplementation may be a simple way to ‘help babies breathe better’, said McEvoy.
Nonetheless, McEvoy underlined that the primary objective remains – which is to get pregnant women to quit smoking despite the observed benefits of vitamin C. “[Smoking] is the singlemost preventable cause of perinatal death and increased preterm delivery … [yet] many do not realize that the foetal lung is very sensitive to the effects of in-utero smoke,” she said.
The researchers intend to follow the children up to 6 years to establish the long-term effects of vitamin C on respiratory health, particularly asthma, which is difficult to diagnose at the early stages of life.