In the study, which appears in this month's issue of Cancer Epidemiology Biomarkers & Prevention (Vol 15, 1660-1667, September 200), the protective effect of multivitamins early in pregnancy was found to be weakly significant. However, as results were similar to more statistically significant results the Pennsylvania researchers obtained in 1993, they concluded this apparent benefit is unlikely to have occurred by chance.
Doctors already urge pregnant women to take multivitamins containing folic acid early in pregnancy to reduce the risk of neural tube defects such as spina bifida. As such, the finding that a multivitamin could a have anti-cancer properties for babies gives these types of easy-to-take supplements an added boost.
"This current study suggests another possible protective effect for the vitamins," said lead author, Greta Bunin of the Children's Hospital of Philadelphia. "Children whose mothers took multivitamins close to the time of conception seemed less likely to suffer medulloblastoma and primitive neuroectodermal tumours of the brain."
Medulloblastoma is the second most common brain tumour in children, occurring in one in 20,000 children under age six. The tumour appears in the cerebellum, the lower portion of the brain that coordinates movement. Primitive neuroectodermal tumors of the brain (PNET) are similar to medulloblastoma but occur in other parts of the central nervous system.
The collaborative study compared 315 children diagnosed with these tumors before age six to 315 randomly chosen healthy children. The children with cancer were registered with the Children's Oncology Group, an organization of pediatric cancer programs in the US and Canada.
In the periconception period of pregnancy, several months before and after conception, mothers of children with brain tumors were less likely than control mothers to report use of multivitamins (adjusted odds ratio (OR), 0.7; 95% confidence interval (95% CI), 0.4-1.0; P = 0.08).
The researchers found that taking multivitamins later in pregnancy did not significantly reduce a child's risk of medulloblastoma and PNET.
"Our findings suggest that the time close to conception may be a critical period in the development of these tumors," said Dr Bunin.
"However, most women do not yet know they are pregnant at this very early stage. That is why women of reproductive age are advised to take multivitamins to prevent neural tube defects even if they are not trying to get pregnant."
The researchers questioned mothers in a telephone survey. All of the children with cancer were diagnosed between 1991 and 1997.