Fattening pollutants? Chemicals in mother’s blood contribute to child’s obesity, study suggests

Published online October 5 ahead of print in the peer-reviewed journal Environmental Health Perspectives (EHP), the study examined data collected between 2004 and 2006 on a representative sample of 518 Spanish women in their first trimester of pregnancy. Among babies whose mothers were normal weight pre-pregnancy, those babies whose mothers had DDE levels in the top 75 percent of exposure were twice as likely to grow rapidly during their first 6 months as babies whose mothers had the lowest DDE levels. Infants in the top 50 percent of exposure were three times more likely to have high BMI scores at 14 months. The researchers did not observe an association between DDE and weight for babies of mothers who were overweight before pregnancy.

Two other human studies have shown an association between prenatal DDE exposure and obesity later in life. "However, this analysis suggests, to our knowledge for the first time, that fetal DDE exposure may promote rapid growth starting in the immediate postnatal period," report lead author and epidemiologist Michelle A. Mendez, of the Centre for Research in Environmental Epidemiology, and her colleagues. Laboratory studies have suggested that "exposure to chemicals with endocrine-disrupting properties might promote shifts in appetite regulation, but may also promote obesity through metabolic changes," says Mendez.

Only 14 percent of all the children had a BMI exceeding the 85th percentile, but rapid growers of both normal-weight and overweight mothers were five times more likely than other babies to have a high BMI at 14 months. Other studies have shown that infants who grow rapidly also tend to have higher levels of body fat. More than 40 studies have associated rapid weight gain in the first few months of life with obesity and metabolic disorders later in life, the team writes.

The team tested the mothers' blood serum for other organochlorine compounds with endocrine-disrupting properties, including polychlorinated biphenyls (PCBs), but these chemicals showed no association with early weight gain. The researchers controlled for other factors in rapid growth and high BMI, such as parents' height and weight, duration of breastfeeding, and whether the mother smoked. The team is continuing to study the children, who are now 4 years old.

"Most of the exposure to organochlorine compounds is thought to come from the diet," says Mendez. Foods including meats, fish, dairy products, and fruits and vegetables are potential sources of exposure to DDE and similar compounds. "These chemicals persist in the environment as they are highly resistant to degradation," Mendez says.