NEW YORK, Jul 22 (Reuters) -- Taking vitamins during pregnancy might reduce the increased risk of fetal death in women who smoke, according to a study.
But the risk of fetal death is nearly twice as high in women who smoke as in nonsmoking women, and prenatal vitamins do not eliminate that risk, cautions study co-author Dr. Germaine M. Buck, an associate professor of social and preventive medicine at the State University of New York at Buffalo.
In the study of 12,465 pregnancies, the researchers found that pack-a-day smokers had a 77% higher risk of fetal death compared with nonsmokers. But those who smoked a pack-a-day and took a vitamin supplement had a smaller increase in risk (22%) compared with nonsmoking women.
Although the researchers conclude that "regular use of multivitamin/mineral supplements, particularly among heavier smokers, may reduce the risk of fetal death associated with maternal cigarette smoking," Buck urges smokers not to assume that vitamins will make up for the potential damage smoking can cause to an unborn child.
"It looks like the vitamins are doing something because the risk isn't as high, but the important point is -- it's still a 22% increase in risk (for smokers who take vitamins). So that's really the message. You don't remove the risk entirely," she said.
And the findings of the study need to be confirmed by additional research, she notes. The study relied on the women's ability to recall past smoking and vitamin use, a method that can be prone to error.
Also, women who smoked before, but not during pregnancy, were termed nonsmokers in the study, which may have skewed results, since "prepregnancy maternal smoking may have residual effects," according to the report. Other factors not taken into account were dietary intake, and vitamin type.
"We don't have a sense of what kinds of vitamins women were using. There are so many preparations out there," says Buck. "We don't know if it's a chance finding or not."
Smoking is believed to have detrimental effects on the fetus through several mechanisms, including the production of free radicals, highly reactive particles that can damage DNA and proteins, and through interfering with the availability of certain nutrients.
Thus multivitamin/mineral supplements, which contain free radical-scavenging antioxidants such as vitamins C, vitamin E, and beta-carotene, might counteract at least some of the adverse effects of smoking on fetuses, postulated Buck and fellow researchers, Drs. Tiejian Wu and Pauline Mendola.
The prevalence of cigarette smoking during pregnancy is about 25% in the US, according to the report.
SOURCE: American Journal of Epidemiology 1998;148:215-221.
