Astrocytomas, which form in the large cells of the nervous system, and medulloblastomas, which generally develop in the central part or within the hemispheres of the brain, account for up to about half of childhood brain tumours, note Dr. Thomas Harder and colleagues at Charite-Universitatsmedizin Berlin.
"Remarkably, for both of these types of childhood brain cancer... high birth weight was significantly associated with increased tumour risk," Harder and colleagues report in the American Journal of Epidemiology.
The investigators found this association after looking at the combined findings from eight studies that involved more than 1,7 million children younger than 19 years old. Over 4 000 of these children developed astrocytomas, medulloblastomas, or tumours in the cerebrospinal passageways of the brain known as ependymomas.
In studies reporting the development of astrocytomas, the researchers found that each 1 000 gram increase in birth weight increased risk by 19 percent.
Studies reporting the development of medulloblastomas also showed a significantly increased risk among children who were heavy at birth, but risk did not appear to increase with increasing birth weight, as found with astrocytomas, the investigators note.
By contrast, they found no association between low birth weight and the development of these two tumour types; nor did they identify a link between birth weight and the development of ependymomas in the small number of studies reporting on this type of tumour.
Should follow up research find causal associations between high birth weight and childhood cancers, measures to decrease the incidence of high birth weight may be needed to curb the risk for brain tumours in children, Harder and colleagues conclude.