Overweight Pregnancy Affects Baby Growth

Obese pregnant womens' babies grow at a slower rate

(RxWiki News) Being obese and pregnant can carry a range of risks to the mother during pregnancy, but it also has consequences for her baby, in the short-term and the long-term.

A recent small study has found that the newborns of obese mothers did not grow the same way children of normal-weight mothers did.

Although the study included just under 100 mothers, the results reveal another possible risk factor to consider for overweight pregnant women.

"Get to a healthy weight before attempting to conceive."

The study, led by Katie Larson Ode, MD, an assistant clinical professor in pediatric endocrinology and diabetes at the University of Iowa, involved 97 mothers who were not diabetic and had single, healthy babies at term.

Prior to becoming pregnant, 20 of the women were obese, 18 were overweight and 59 were of an appropriate healthy weight.

The researchers made to visits to the women's babies, once at 2 weeks and once at 3 months. The babies' body composition and other body characteristics were assessed, and the researchers interviewed the mothers about the babies' feeding habits.

Researchers also gathered information from the women's medical records and then primarily focused on comparing the babies' weight, length, body fat mass and non-body-fat mass. (This means they looked at the amount of fat on a baby compared to the amount of non-fat in the babies' weights.)

They found that the data from the children at 2 weeks old did not vary much across all the children, but there were significant differences when the children were 3 months old.

The babies born to overweight or obese mothers gained less weight and grew less in length than the babies born to mothers of a healthy weight. The babies born to overweight moms gained 11 fewer ounces than the babies born to healthy-weight moms.

The babies born to overweight moms also gained less fat mass - 0.3 ounces less - and these results held true even when the researchers took into account possible differences among the babies if they had been breast-fed or not.

The researchers also figured into their calculations which mothers smoked and the blood glucose levels of the mothers, but these calculations did not change the link between overweight moms and slower-growing infants.

"We've found these children are not growing normally," said Dr. Ode. "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."

Dr. Ode said the appropriate response to the findings is not to panic, especially since other studies have shown that the babies of overweight mothers do eventually catch up to their peers.

However, Dr. Ode and her colleagues have two theories about why these babies are smaller in their first several months on earth.

One is that inflammation that occurs in overweight and obese people may be occurring in the pregnant mother and then stimulating the baby's immune system to act up. If the baby's body is spending energy on its immune system, then it has less energy to spend on growing.

The other theory relates to two different ways babies grow and develop in their mother's body. One is through fatty acids sent to the baby from the mother in a hormone called IGF-1, and the other is through hormones sent from the baby's pituitary gland.

It may be that the mother is sending extra fatty acids so the pituitary gland isn't working as hard and therefore slows down the hormones it produces for growth. Then when the baby is born, the gland is behind on producing the hormones to help the baby grow at first.

A study published in 2010 in JAMA noted that six in ten women of childbearing age are overweight or obese, the background info in this study notes. Therefore, it's important that women realize the additional risks of becoming pregnant when they are above a healthy weight.

The study was published July 23 in The Journal of Pediatrics. The research was funded by the National Institutes of Health and the University of Minnesota.

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Review Date: 
August 8, 2012