"The findings of this research are highly applicable to humans," said Eliot Spindel, M.D., Ph.D., a scientist in the Division of Neuroscience at the Oregon National Primate Research Center and senior author of the paper. "The sad reality is that approximately 11 percent of pregnant mothers continue to smoke during pregnancy -- this translates to about a half a million American women a year. Reflecting the highly addictive nature of smoking, these women continue to smoke despite the warnings of their physicians and despite a tremendous public awareness campaign aimed at preventing smoking during pregnancy. While this research finding may assist the babies of these mothers, it does not make smoking during pregnancy more acceptable. It would only become a last resort treatment when an expectant mother is unwilling to stop smoking."
Smoking during pregnancy can cause premature delivery, growth retardation and has been blamed for 5 percent to 10 percent of all fetal and neonatal deaths. Maternal smoking can also cause decreased pulmonary function and increased respiratory illness in offspring. Previous research by the Spindel lab demonstrated that nicotine is a key cause of these lung development problems. Specifically, nicotine crosses the placenta where it interacts with cells in the unborn infant's developing lungs.
While past research in the Spindel lab has helped define how nicotine causes these changes, many of the specific mechanisms for infant lung development problems remain unknown. However, previous research has clearly shown that infants born to smoking mothers often suffer from reduced lung air flow.
To conduct this research, scientists studied a small group of infant monkeys born to mothers who received regular doses of nicotine -- doses comparable to those of a smoking human mother. The breathing abilities and lung development of these monkeys was then compared with monkeys born to mothers who had received both nicotine and vitamin C doses during pregnancy. A third group of baby monkeys that did not receive either nicotine or vitamin C during prenatal development were studied as a control group.
"We found that animals exposed to nicotine prior to birth had reduced air flow in the lungs compared to animals that were given nicotine and vitamin C. In fact, the nicotine plus vitamin C group had lung air flow close to that of a normal animal," explained Spindel. "Other notable observations were that increased levels of surfactant apoprotein B protein normally caused by nicotine were reduced by vitamin C. In addition, elastin levels in the lungs appeared to be slightly impacted by vitamin C. This finding may be significant as elastin plays a key role in the expansion and contraction of lung during breathing."
"Smoking remains a very significant problem during pregnancy and also during infancy," explained Michael Gravett, M.D., chief of maternal-fetal medicine in the Department of Obstetrics and Gynecology, OHSU School of Medicine, and a researcher at ONPRC. "While we strongly encourage all women to quit smoking, this is not always possible. These data suggest that vitamin C may be an important tool in preventing smoking-induced adverse outcomes."
While the research demonstrates vitamin C's promise for counteracting the effects of nicotine on lung function, scientists note that vitamin C did not counteract other negative health impacts of smoking during pregnancy such as abnormal brain development and decreased body weight. The scientists also caution that more research is needed in regard to determining the appropriate vitamin C dosage for humans. Finally, studies need to be conducted to demonstrate that giving pregnant women higher levels of vitamin C will not itself cause development problems.
The ONPRC is a registered research institution, inspected regularly by the United States Department of Agriculture. It operates in compliance with the Animal Welfare Act and has an assurance of regulatory compliance on file with the National Institutes of Health. The ONPRC also participates in the voluntary accreditation program overseen by the Association for Assessment and Accreditation of Laboratory Animal Care International (AAALAC).