It is well known that pregnant overweight or obese women have a higher risk for numerous health complications. A new study published in the Journal of Pediatrics now reveals that the added weight also seems to have an impact on children’s growth and development, at least during the first stage of their lives.

Researchers from Iowa University compared infants’ birth weight and height between overweight and obese mothers with normal-weight mothers and discovered that from birth to the age of three months, babies of overweight/obese mothers gained less weight, grew less in length and gained less fat mass compared to those born to normal-weight women. In infants, fat mass is widely believed to be crucial to brain growth and development, which may explain why humans have the fattest newborns of any mammal.

Katie Larson Ode, assistant clinical professor in pediatric endocrinology and diabetes at the UI says:

“We’ve found these children are not growing normally. If what we have found is true, it implies that the obesity epidemic is harming children while they are still in utero and increases the importance of addressing the risk of obesity before females enter the child-bearing years, where the negative effects can affect the next generation.”

A 2010 study published in the Journal of the American Medical Association reports that 6 in ten women of childbearing age in the U.S. are overweight or obese. Previous studies have shown that children of overweight or obese mothers usually catch up to their normal-weight-mother peers at some point, but unfortunately they are also subject to a higher risk of continuing to rapidly gain weight in adolescence and becoming overweight or obese themselves, which can cause health problems throughout their lives.

Larson Ode declares: “A message from this study is, ‘Don’t panic,’ Pediatricians see a lack of (initial) growth, and they assume the child is not getting enough nutrition. But we believe the baby is in fact getting plenty.”

The team combined the literature to find an explanation and hypothesize that the underlying reasons for the slower physical development of babies born to overweight or obese women could either be due to two reasons. The first one being inflammation, as fat cells that normally help to suppress the immune system flare up in overweight adults. The team believes that this reaction in overweight and obese pregnant women’s immune system could also inflame the fetus’s developing immune system and therefore divert energy that would otherwise be used for the baby’s development.

Senior author Ellen Demerath, from Minnesota University explains: “These (fat tissue-derived) hormones and inflammatory factors tend to have appetite/satiety regulating effects early on, and may exert their negative effects on growth both during gestation and through passage into the breast milk during postnatal development as well.”

The second reason involves the growth of babies in the womb, which occurs in two ways, i.e. through free fatty acids delivered by the mother via a growth hormone called IGF-1 and through a growth hormone secreted by the baby’s brains pituitary gland. The researchers hypothesize that the baby receives so many free fatty acid-derived growth hormones from its overweight mother that the pituitary gland slows its production, which means that when the baby is born, the pituitary gland is insufficiently enough developed to compensate. Larson Ode, who works at the Carver College of Medicine comments: “It’s just not mature yet.”

The study involved a total of 97 non-diabetic mothers, including 38 overweight or obese mothers and 59 normal-weight mothers. The findings revealed that between the age of 2 weeks to three months, babies of overweight/obese mothers gained 11 ounces less in weight, gained 0.3 ounces less fat mass and grew nearly a half-inch less compared with babies of normal-weight mothers.

The team is aware of the fact that the sample size of their study was small and noted that further research needs to be conducted with larger populations.

Written by Petra Rattue