Women who experience excessive weight gain during pregnancy may increase their child's risk of developing early-onset bowel cancer, according to health experts. These early life exposures could alter a child's biological trajectory, potentially making them more susceptible to the disease in adulthood.
This concern comes amid a notable rise in colorectal cancer diagnoses among young people. In the UK, over 2,700 cases are diagnosed annually in individuals under the age of 50. While historically, later-life factors like smoking have been emphasized for cancer risk, experts now highlight the significance of prenatal conditions.
Dr. Rosiered Brownson-Smith, an expert in diet, lifestyle, and health at King's College London, stated that maternal obesity and excessive weight gain during pregnancy are recognized as factors that may increase the risk of early-onset colorectal cancer. "This can change the trajectory of a child's life, potentially predisposing them to some early susceptibility that will only come to fruition later in life," she explained.
Research suggests that maternal obesity during pregnancy is associated with more than double the colorectal cancer risk in offspring. This can occur through two primary pathways. Firstly, children born to obese mothers are more likely to become obese themselves, which is an independent risk factor for a five-fold increase in bowel cancer risk. Secondly, a mother's weight can directly influence the developing gastrointestinal tract in the womb, making it more susceptible to later lifestyle triggers.
"When cancer occurs, it's not just caused by one event," Dr. Brownson-Smith noted. "Rather it's the culmination of lots of mutations that build up slowly over time." She posits that early imprints from the prenatal environment could represent initial biological changes that heighten risk, potentially preparing gut cells to mutate more readily.
Birth weight is also considered a factor, with overweight mothers more likely to deliver larger babies. A study from the Yale School of Public Health indicated that each additional half-kilogram of birth weight was associated with a 10% higher risk of developing early-onset colorectal cancer in girls. The prevailing theory is that birth size reflects the intrauterine environment, which may program long-term metabolic changes influencing cancer risk. Previous studies have also suggested that excess maternal weight can disrupt growth hormone production during pregnancy, potentially impacting a child's long-term health.
Experts suggest these early life imprints might contribute to the increasing rates of bowel cancer in younger demographics. "There is some evidence that this early life imprinting may be contributing to the increase of young bowel cancers," Dr. Brownson-Smith said. She added that modern lifestyle factors, such as reliance on ultra-processed foods and sedentary habits, also increase risk in young people, especially when traditional risk factors are absent.
Obesity is identified as a significant contributor to rising bowel cancer rates among the young. It is the only known behavioral risk factor that has increased in younger adults over the past two decades, while other factors like alcohol consumption and physical inactivity have remained stable or improved. Maintaining a healthy weight is estimated to prevent approximately 20% of bowel cancer cases. Experts recommend increasing fiber intake and physical activity to mitigate risk.
Despite obesity's role, researchers believe it alone does not fully explain the overall increase in young people diagnosed with the disease, suggesting that early-life exposures likely play a crucial part.