Children born to obese mothers are 57% more likely to develop cancer before the age of five: Study
Children born to very obese mothers - those with a pre-pregnancy body mass index (BMI) of 40 or higher - have a 57% higher risk of developing leukemia before they turn five, according to an analysis of nearly two million birth records and 3,099 cancer registry records filed in the state of Pennsylvania, US, between 2003 and 2016.
The study - which states that children born to obese mothers are more likely to develop cancer in early childhood - is significant as little is known about the risk factors of most childhood cancers, except for specific socio-demographic differences and inherited genetic mutations. The study shows it is not merely that larger women were giving birth to larger babies or that heavier women tended to be older - known risk factors for childhood cancer - but rather, a mother’s size independently contributes to her child’s risk. “Our study identified a novel association of mother’s obesity with risk of cancer, particularly leukemias, in children, even after adjustment for maternal age and race, two established risk factors for childhood cancer,” says the research team from the University of Pittsburgh Graduate School of Public Health and UPMC Hillman Cancer Center.
According to the researchers, the root cause of the effect they see in their analysis may have something to do with insulin levels in the mother’s body during fetal development, or possibly changes to the mother’s DNA expression, which are passed on to the child.
The team says what is critical is that their analysis shows not all levels of obesity carry the same risk. Among the obese women in the study, higher BMI came with higher cancer rates in their children. So, even small amounts of weight loss can translate to a real reduction in risk, says the team. The researchers recommend preventative measures and say that maintaining a healthy weight is good, both for the mother and the child.
Cancer in children, say the researchers, is relatively rare but remains the “leading cause of death by disease past infancy in children in the US”. The incidence of all cancers in children under 15 years of age is 16.4 per 100,000. The team says that although childhood cancer mortality rates have decreased by 63% from 1970 to 2012 - which could be attributed to improved treatment - approximately 1,790 children die from cancer in the US every year.
“The analysis included 1,827,875 infants (13,785,309 person-years at risk), with 2,352 children diagnosed with any cancer and 747 with leukemia before age 14. Children born to mothers with a body mass index of over 40 kg/m2, had 57% (12-120%) higher leukemia risk. Newborn size 30% higher than expected was associated with 2.2-fold and 1.8-fold hazard ratio for total childhood cancer and leukemia, respectively, relative to those with expected size. Being less than 30% of one’s expected size also increased the total cancer risk. Newborn size did not mediate the association between maternal obesity and childhood cancer. The results suggest a significant role of early life exposure to maternal obesity- and fetal growth-related factors in childhood cancer development,” says the paper.
There has been growing interest regarding the impact of maternal obesity on childhood cancer. The reason, says the study, is that nearly 40% of adults, and women of child-bearing age, in the US are obese. The researchers say that while obesity has been linked with an increased risk for many adult cancers, its potential role in the development of childhood cancer, including leukemia, was not clear till now, prompting them to conduct extensive research on the topic.
Among other findings, analysis shows that older maternal age was associated with increased risk of childhood cancer and leukemia, whereas non-white race was associated with lower risk. Besides, the mother’s weight gain during pregnancy was associated with a higher risk of neuroblastoma. “Children born to mothers with pre-pregnancy weights of 90-99 kg and greater than or equal to 100 kg were at 46% and 42% higher risk of leukemia, respectively. Maternal height and weight gain during pregnancy were not associated with a higher risk of childhood total cancer or leukemia,” says the study.
The researchers recommend more studies on the subject. “Our findings, if confirmed by studies in other populations, would provide a rationale for weight control of would-be mothers as a possible preventive measure against the risk of cancer in children,” says the paper.
The findings were published in the American Journal of Epidemiology.