Though it’s well established that smoking during pregnancy is not good for fetal health, some women who smoke have difficulty quitting the habit during pregnancy. Now, according to new research, there may be a way to help protect the lung function of infants born to such women: a simple daily vitamin C pill.
The findings were described in a study released in JAMA in concert with its presentation at the American Thoracic Society meeting in San Diego on Sunday.
Researchers from Oregon Health & Science University in Portland randomly assigned a group of 179 pregnant women who smoked to receive either a daily 500 mg vitamin C pill or a placebo pill during the early stages of pregnancy. When the investigators assessed the newborns’ with standardized pulmonary function tests within 3 days of birth, they found that 2 important measures of lung function (the ratio of time to peak tidal expiratory flow to expiratory time and the passive respiratory compliance) were significantly better in newborns of mothers who took vitamin C compared with those who did not. At 1 year of age, however, these differences on pulmonary function tests were no longer significant.
However, at 1 year of age, the percentage of infants who had wheezing, as reported by their primary caregivers, was significantly different between the two groups: 15% in the vitamin C group vs 30% in the placebo group.
Lead author Cindy McEvoy, MD, MCR, discussed these findings with news@JAMA.
news@JAMA: Why did you conduct this study?
Dr McEvoy: Unfortunately, 50% of pregnant smokers are unable to quit smoking during pregnancy, and this has significant negative effects on the fetus, particularly on their future lung function and asthma risk. We had compelling preliminary data from studies in monkeys to support our hypothesis that daily vitamin C may help improve the babies’ lung function, and did this study to investigate this possibility.
news@JAMA: The primary measures of lung function that you found to be better in infants of the vitamin C group were the ratio of time to peak tidal expiratory flow to expiratory time, and the passive respiratory compliance. What do these measures actually mean in terms of how well the infants’ lungs are working?
Dr McEvoy: Basically, it means that the lungs are less stiff—in other words, more compliant. The small airways of the lungs are healthier, so it is easier to move air in and out when breathing. When moving air in and out of the small airways becomes difficult, wheezing occurs.
news@JAMA: Why did you no longer see a difference in lung function testing at 1 year of age? How do you explain the differences in wheezing observed at 1 year when there was no difference in lung function measures?
Dr McEvoy: One possibility for why we didn’t see differences in the 1-year pulmonary function tests is because we were only able to get this testing on about two-thirds of all the infants studied at delivery. Also, the pulmonary function tests at 1 year were done with the infants sedated, while the newborn tests were done with nonsedated infants. The use of passive respiratory mechanics at 1 year may have been less sensitive to detect lung function abnormalities. In terms of wheezing, we were able get this history from more than 90% of the patients studied at delivery, so that may have accounted for the differing results.
news@JAMA: Are you going to follow up these infants longer? What are the next steps for this research?
Dr McEvoy: Yes, we are currently getting follow-up respiratory histories on these infants. We are also doing additional studies looking at more sensitive pulmonary function tests, as well as some potential epigenetic changes caused by smoking during pregnancy that can be potentially prevented by vitamin C.
news@JAMA: Even though taking vitamin C during pregnancy seems to help with infant lung function at birth, you mention in your article that, importantly, it does not negate the other negative effects of smoking during pregnancy on newborn health. So what is the take-home message for pregnant smokers, based on this study?
Dr McEvoy: The ideal solution is still for pregnant smokers to quit smoking. But if they are unable to quit, vitamin C may be helpful for their infants’ lung function.