But the findings aren't rock solid and need more study, write Greta Bunin, PhD, and colleagues in Cancer Epidemiology Biomarkers & Prevention.
Bunin is on staff at Children's Hospital Philadelphia and the University of Pennsylvania.
Before you read about the study, know this: Brain tumors are rare in children, and doctors can't always tell why they occur.
Bunin's team doesn't promise that prenatal vitamins will prevent kids' brain tumors. The researchers also aren't blaming kids' brain tumors on women who don't take multivitamins.
About the Study
The researchers interviewed the kids' moms about their diet and vitamin use in the year before pregnancy and during pregnancy.
For comparison, they also interviewed the mothers of 315 children without brain tumors.
All of the kids lived in the U.S. or Canada.
The interviews were conducted by telephone and lasted nearly an hour, on average.
The mothers who reported taking multivitamins close to the time of conception were 30% less likely to have a child diagnosed with a brain tumor before the child's 6th birthday, the study shows.
The researchers say those findings were weaker than their previous study. They also note that the women may not have accurately recalled their vitamin use.
The study's finding is "of only borderline significance," the researchers write. That means that the results could possibly be due to chance, based on statistics.
But since their previous work also found a possible (and stronger) link between moms' multivitamin use and lower risk of kids' brain tumors, Bunin's team says the findings are "unlikely" to be due to chance.
The study doesn't distinguish between multivitamins and prenatal vitamins. The researchers suggest making future studies more specific about what multivitamins were used.