Vitamin C supplements can help pregnant smokers reduce the amount of damage they do to their babies.

Tragically, over 10 per cent of Australian women admit to smoking during some or all of their pregnancy.

There is clear evidence showing infants born to smokers give decreased pulmonary function test (PFT) results, increased incidence of childhood asthma and hospitalisation rates.

But it appears some of this risk can be reduced by vitamin C supplementation.

In an earlier study involving primates, vitamin C blocked some of the in-utero effects of nicotine on lung development and pulmonary function in offspring.

In their latest study, researchers randomly assigned pregnant smokers to receive vitamin C (500 mg/d) or a placebo.

159 newborns of pregnant smokers (76 vitamin C treated and 83 placebo treated) and 76 newborns (reference group) of pregnant nonsmokers were studied with newborn PFTs, performed within 72 hours of birth.

The researchers found that newborns given vitamin C, compared with those randomized to receive the placebo, had improved measures of pulmonary function.

Offspring randomized to vitamin C had significantly decreased wheezing through their first year (15/70 [21 percent] vs 31/77 [40 percent]).

There were no significant differences in the 1-year PFT results between the vitamin C and placebo groups.

“Although smoking cessation is the foremost goal, most pregnant smokers continue to smoke, supporting the need for a pharmacologic intervention,” the authors write.

Other studies have demonstrated that reduced pulmonary function in offspring of smokers continues into childhood and up to 21 years of age.

“This emphasises the important opportunity of in-utero intervention. Individuals who begin life with decreased PFT measures may be at increased risk for chronic obstructive pulmonary disease.”

“Vitamin C supplementation in pregnant smokers may be an inexpensive and simple approach (with continued smoking cessation counselling) to decrease some of the effects of smoking in pregnancy on newborn pulmonary function and ultimately infant respiratory morbidities, but further study is required,” the researchers conclude.

“The findings... offer an approach for potentially minimizing the harmful effects of maternal smoking during pregnancy on the respiratory health of infants,” writes Dr Graham Hall from the University of Western Australia.

“However, achieving smoking cessation should be the primary goal for women who smoke and who intend to or become pregnant. By preventing her developing foetus and newborn infant from becoming exposed to tobacco smoke, a pregnant woman can do more for the respiratory health and overall health of her child than any amount of vitamin C may be able to accomplish.”