New research from the International Childhood Cancer Cohort Consortium (I4C) confirms that childhood cancer is linked to birthweight. The incidence of childhood cancer appears to be slowly rising, at a rate of approximately 1% per year in developed countries.

Link between birthweight and cancer

Risk rose by 26 percent for every kilogram increase in birthweight for all cancers. The I4C is an alliance of several large-scale prospective cohort studies of children that pools data and biospecimens from individual cohorts to study various modifiable and genetic factors in relation to cancer risk. It found that the occurrence of childhood cancer rises as birthweight increases.

The study observed that risk rose by 26 percent for every kilogram increase in birthweight for all cancers. In younger children, the risk for leukemia appears to be higher than for all cancers combined, but in children diagnosed at or after three years of age, cancers other than leukemia are more strongly related to high birthweight.

It’s not the mother’s weight gain

The research also found that the risk associated with birthweight is unlikely to be primarily due to the mother’s weight gain during pregnancy, one of the contributors to birthweight.

“We have been able to compile a significant amount of evidence that effectively shows that childhood cancer incidence rises with increasing birthweight,” said Professor Terry Dwyer, the Executive Director for The George Institute for Global Health. “While we observed a correlation between increased birthweight and higher risk of cancer incidence in children, there were no significant interactions with maternal pre-pregnancy overweight or pregnancy weight gain.”

Dwyer, a Professor of Epidemiology at the Oxford Martin School and the Nuffield Dept. of Population Health, leads the I4C, one of the largest initiatives in understanding the role of early-life exposures in childhood cancers. The current knowledge of cancer risk factors to date is mainly based on adult research studies.

Prior to joining The George Institute, Dwyer was previously at the International Agency for Research on Cancer (IARC)—a WHO division—in France. Earlier in his career, Dwyer led groundbreaking research into Sudden Infant Death Syndrome (SIDS) where he contributed important evidence confirming that sleeping position was a major cause of Sudden Infant Death Syndrome (SIDS), leading led to a vast reduction in SIDS deaths around the world.

The power of the collaboration

I4C allows the simultaneous examination of a wider range of potential factors. The relationship between childhood cancers and high birthweights have been posited in previous studies, but the collaboration of I4C allows the simultaneous examination of a wider range of potential factors including maternal age, marital status, education level, smoking propensity, previous live births, diabetes, pre-pregnancy BMI and total pregnancy weight gain.

Globally, there exists a difference in average birthweights across different countries. For example, birth weight in northern Europe is higher than southern Europe; and there is a higher incidence of leukemia, the most common childhood cancer, in northern Europe.

What’s next?

I4C researchers plan to follow this study up with several lines of inquiry, including:

• Looking at data in new cohorts such as in Japan and China to see whether this association exists there as well
• Investigating other factors that have some relationship to birth weight, such as birth order, to see whether the association is similar in infants of different birth order, and
• Making cord blood measurements from infants in the cohorts to determine whether growth hormones of various types explain what we have found.

Professor Dwyer concludes:

“At The George Institute we are focused on the prevention and treatment of non-communicable diseases, like cancer. I am more optimistic that we’ll find ways of preventing childhood cancer than I was when we started this study 10 years ago. We know that there are no easy answers, but we are assembling more clues, like this piece of evidence, which will help us fill in the puzzle. Additional research into childhood cancer is needed so that we can provide actionable solutions to improve outcomes for future generations.”