Expectant mothers who take multivitamins fortified with folic acid not only guard against birth defects, but also reduce the risk of three common childhood cancers, according to new research.

"I knew they were important, and this study just reinforces that," mother-to-be Summer MacDonald told CTV News.

Researchers at Toronto's Hospital for Sick Children say multivitamins are associated with:

• a 47 per cent protective effect against neuroblastoma,
• a 39 per cent cut in rates of leukemia
• and a 27 per cent drop in rates of brain tumours.

This research was published online in the journal Clinical Pharmacology & Therapeutics.

"Here is a relatively non-expensive way to give prenatal vitamins and to prevent one of the worst outcomes in medicine for a family -- a child with cancer," Dr. Gideon Koren, a senior scientist in the SickKids Research Institute who led the study, told CTV News.

Women considering pregnancy have long been advised to take folic acid to prevent congenital defects such as spina bifida. But these latest findings suggest that supplementing with a multivitamin containing folic acid may be even better.

Surveys show that fewer than half of Canadian women take prenatal multivitamins before or during pregnancy, a number doctors say needs to be increased significantly.

"Women planning pregnancies should be highly encouraged to take prenatal vitamins," said Koren.

He says taking a multivitamin is a simple step that any mother can take to help protect the health of her child before and during pregnancy.

"This affordable approach could contribute to a significant reduction in the number of childhood cancer cases diagnosed each year, which has huge implications for society at large," he said.

While other studies have looked at the effect of prenatal vitamins on rates of pediatric tumours, this is the first meta-analysis of prenatal multivitamin use before and during early pregnancy and its protective effect for several cancers.

The researchers aren't sure which components of a prenatal multivitamin offer protection against pediatric cancers but say additional research is needed.

Leukemia is the most common childhood cancer and accounts for 25 to 35 per cent of new pediatric cases each year.

Brain and spinal tumours, the second most common form of cancer, account for 17 per cent of new pediatric cancer cases each year. And neuroblastoma, the most prevalent solid tumour that occurs outside of the brain in children under the age of five, affects one in every 6,000 to 7,000 children in North America.

Dan Mornar is pleased with the finding. He watched his son Jonathan die after developing neuroblastoma and now counsels other parents dealing with a child who has cancer with the British Columbia Childhood Cancer Parents' Association. 

"I'd like to be out of a job because cancer was cured or better managed. And prevention here is a key," he said.

With a report from CTV's Avis Favaro and Elizabeth St. Philip