Weighing up the risk: The relationship between maternal obesity and bowel cancer risk

In the past week a number of media outlets (The Guardian, The Herald) have covered the findings from research investigating the link between maternal obesity and the rise in numbers of bowel cancer cases in younger adults (aged <50 years).

According to the World Health Organization obesity is a global issue affecting all nations, which has tripled since 1975. Obesity, which is the abnormal accumulation of body fat, has been linked to many illnesses including cancer.

Researchers have shown a clear link between obesity and cancer, but there has been little research investigating the evidence linking maternal obesity with the risk of their children developing cancer later in life.

Researchers at the University of Texas Health Science Centre (Texas, USA) have attempted to answer this very important question on the association between maternal health and health outcomes for their babies later in life. In this study, they focused on the link between maternal obesity and the risk of bowel cancer developing in their children. This work was published on August 21^st 2021 in the British Medical Journal Gut.

What did the study involve?

The study investigated the relationship between maternal obesity for 14,000 Californian mothers who were pregnant and delivered babies in the 1959-1966 period. The team collected information from the expectant mothers’ medical records in the six months leading up to their pregnancy, throughout the duration of their pregnancy, and following delivery. This included detailed analysis of patient demographics such as their race, educational status, and social status. Some women in the study had more than one child. The researchers then traced the health of 18,000 children of those women up to 2019 using reports from the Cancer registry in California to track the number of children who went on to develop bowel cancer later in life.

What did the researchers conclude?

One of the key findings from this study was that 68 children of the mothers were diagnosed with bowel cancer over the follow-up years studied, with around half (48%) being diagnosed under the age of 50. The researchers found that there was a strong link between a high birth weight (more than 4 kilograms) and weight gain during early life. The researchers also reported a strong link between maternal obesity (≥30 kg/m²) and the risk of a child developing bowel cancer later in life doubling. The researchers went on further to say that the events taking place in the womb during pregnancy, plays a significant part in the biology of bowel cancer development. The researchers concluded that with the rising levels of obesity in the population, the number of bowel cancer cases is likely to continue rising in the future. This will have direct implications for the diagnosis and treatment of bowel cancer.

How did the media cover this study?

Since its publication, 23 news outlets have published the findings from this publication. The headlines summarised the key finding from the study, potential association between maternal obesity and bowel cancer risk. This study was covered by the Guardian under the heading “People whose mothers were overweight at higher risk of bowel cancer, study suggests” and The Herald “Is surge in maternal obesity behind the mystery rise in bowel cancer among young people?”. Both media outlets provided a balanced overview of the conclusion of the study by associating obesity with bowel cancer risk without claiming maternal obesity directly causes bowel cancer. Both the Guardian and The Herald accurately summarized the key points discovered from the study and described the conclusions from the study in a manner that was easy to understand.

Media coverage of the study highlighted that maternal obesity can elevate the risk of bowel cancer later in life, with the Guardian using direct quotes from other researchers that were not directly involved in the study. These quotes were broadly in agreement that the conclusions from the study were likely plausible. A limitation in the media coverage of this study was attributing obesity as a public health challenge in developed nations. It is becoming increasingly apparent that obesity is a global phenomenon with growing incidence of obesity observed across developing nations.

Conclusions

Overall media coverage of this publication was carried out in an objective manner and with a good balance of interpreting the science and presenting national statistics or quotes from cancer organizations. In terms of the publication, it is one of the largest studies of its type. This publication will be useful in paving the way for future work studying the impact of maternal health on their children’s health outcomes.