Obesity is a growing problem among pregnant women and nursing mothers, and researchers are investigating how their weight status might affect the health of their babies. To learn more, School of Public Health researchers studied breast milk samples and found that those belonging to obese mothers contained elevated levels of a protein linked to increased risk of chronic diseases, such as heart disease and type 2 diabetes.

“The consequences of infants receiving high levels of C-reactive protein through breast milk are currently unknown,” says lead author and post-doctoral fellow Kara Whitaker. “However, given that elevated levels are associated with an increased risk of many chronic diseases, this may have important implications for intergenerational transmission of disease risk.”

The study was recently published in the journal Obesity and used data from the school’s ongoing MILK (Mothers and Infants LinKed for Healthy Growth) study.

The researchers tested the milk for C-reactive protein (CRP) because of its link to chronic diseases and previous research showing that it exists in high amounts in the blood of people with obesity. Whitaker and her colleagues are concerned that babies who ingest high levels of CRP through breast milk could be placed at higher risk for disease.

The study examined milk samples from 134 women and found that women with obesity had 1.4 times more CRP in their breast milk as compared to normal weight women. Also, women with obesity who gained excessive weight during pregnancy had 4-7 times more CRP in their breast milk as compared to normal weight women who gained the recommended amount of weight during pregnancy.

“Given the important implications for intergenerational transmission of disease risk, our next step is to examine the associations of CRP in breast milk with infant outcomes — including weight status,” says Whitaker.

In light of the initial link between heavier mothers and elevated CRP levels in their breast milk, the researchers still encourage all women — including those with obesity or who gained excessive weight during pregnancy — to breastfeed their infants.

“There is abundant evidence documenting both the short and long-term health benefits for the child, and our findings should not discourage any woman from breastfeeding,” says Whitaker. “More research is needed before any recommendations can be made.”