Studies have looked at the relationship between children’s weight when they are born (birth weight) and their risk for certain childhood cancers.
Low birth weight and cancer
Most childhood cancers are not associated with low birth weights. However, some studies have shown that there is a link between very low birth weight (less than 1500 g or about 3.3 pounds) and childhood hepatoblastoma (a type of liver cancer). It is not clear how very low birth weight contributes to this childhood cancer. Researchers continue to study the risk for other types of childhood cancers and very low birth weight.
High birth weight and cancer
There is some evidence that a high birth weight is associated with an increased risk of certain childhood cancers. Babies with an increased birth weight (4000 g or more or about 8.8 lbs) seem to have an increased risk of developing leukemia, certain types of brain tumours (such as astrocytoma) and possibly other types of childhood cancer. Why a heavier birth weight contributes to childhood cancer is not really known. Researchers have considered a number of factors, such as the baby may be exposed to high levels of growth factors while in the womb, increased growth of the baby in the womb, a genetic abnormality that may occur in the baby before it is born or other factors.
Some studies have also shown a positive association between high birth weight and adult cancers, such as breast, prostate, uterine and colon cancer. The evidence of a connection between high birth weight and adult cancers is less consistent than for childhood cancers. Studying the relationship between birth weight and cancer in adults is much more difficult because people may be exposed to many other risk factors during the period of time between birth and the onset of cancer.
More studies are needed to clarify why birth weight may increase the risk of developing certain cancers.