Maternal obesity may harm babies' immune system at the time of their birth, according to a new study.

Almost 60 percent of women of childbearing age in the United States are overweight or obese. Due to our more sedentary lifestyle, obesity is a major public health issue, and has been linked to health problems like heart disease, cancer and hypertension. It can even complicate pregnancy by increasing the mother's risk of having gestational diabetes, preeclampsia, preterm birth or a baby with birth defects.

Previous research has also linked maternal obesity to several adverse health outcomes for the infant that can persist into adulthood, such as type-2 diabetes, heart disease and mortality.

Now, researchers at the University of California, Riverside have shown that the immune system becomes compromised - leading to such harmful conditions - very early in a baby's life.

They published their findings in the journal Pediatric Allergy and Immunology.

The team analyzed umbilical cord blood samples of infants born to 39 mothers from the Portland, Ore. area. Of the participants, 11 were lean, 14 were overweight, and 14 were obese mothers. A mother was considered overweight if her body mass index (BMI) was 25 to 29.9, whereas a mother was considered obese if her BMI was 30 or higher.

The mothers were all non-smoking, had no diabetes, had an uncomplicated gestation at term, and were of various ethnicities.

Taking all these factors into account, the research team found that pre-pregnancy maternal weight has a significant impact on the immune system of developing children. (Scroll to read on...)

"A number of studies have linked maternal obesity - starting pregnancy with excess weight and gaining a lot of weight during pregnancy - to a higher incidence of cardiovascular disease and asthma in children," lead study author Ilhem Messaoudi said in a statement. "Our study offers potential links between changes in the offspring's immune system and the increased susceptibility and incidence of these diseases later in life."

Specifically, Messaoudi and her colleagues noticed that in babies born to moms with high BMIs, certain immune cells in circulation - monocytes and dendritic cells - were unresponsive to bacterial antigens compared to babies born to lean moms. These infants also had a lower number of CD4 T-cells, which are involved in the immune response.

This, researchers say, could explain for compromised responses to infection and vaccination in newborns.

Furthermore, the researchers found that cells (eosinophils) that play a role in allergic response and asthma pathogenesis were significantly reduced in the umbilical cord blood of babies born to obese mothers. One potential explanation for these observations is that these cells have already moved into the lungs, which could explain the increased incidence of asthma observed later in life in children born to obese mothers.

This study is the first to show a link between maternal obesity during pregnancy and a hindered immune system in infants at the time of their birth, and thus "could change how we respond to vaccination and how we respond to asthma-inducing environmental antigens," Messaoudi added.

In the first two years of life, children typically receive a myriad of different vaccines. Some parents may be skeptical of such vaccines due to a risk for autism, but prior research has proven that this is a popular misconception. Now, after these latest findings, researchers are asking themselves: "Are the responses to vaccines in infants born to obese moms also impaired in the first two years of life? Should we change how often we vaccinate children born to obese moms? Should we change practices of how much and how often we vaccinate?"

For now, the team recommends that any woman who is pregnant or thinking of becoming pregnant talk to a healthcare professional about managing her weight in order to best assure that she gives birth to a healthy baby.

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