A new study shows that pre-pregnancy obesity is strongly associated with infant mortality. And not only that, but following pregnancy weight-gain guidelines seems to have a limited impact on that mortality risk.
The study—the largest of its kind to date—examined birth and death records of more than six million newborns in 38 states from 2012 to 2013. The authors looked at the mother's height and weight prior to being pregnant, and studied the overall infant mortality in three major categories: infants who died from preterm-related causes, congenital anomalies, and sudden unexpected infant death.
Here's what they found: Infant mortality rates were twice as high for obese women (175 pounds and heavier for a woman 5 feet, 4 inches) than for normal-weight women (110 to 144 pounds at the same height). Deaths from congenital anomalies and sudden infant death also were higher among babies born to obese mothers. In fact, mortality rates rose consistently across obesity categories.
Researchers also found a general lack of adherence to guidelines issued by the Institute of Medicine in 2009 that recommend a weight gain of 11 to 20 pounds for mothers with a pre-pregnancy BMI in the obese range. But even when mothers' weight gain fell within the recommended range, there was not much impact on infant mortality rates.
"These findings suggest that 60 to 75 percent of mothers aren't following the guidelines," said lead author Eugene Declercq. "And even when they do, adherence does little to lower infant mortality."
So now what?
Declercq said the findings suggest the importance of physicians addressing the issue of obesity before pregnancy begins, as well as the need for more research into the underlying processes that might link pre-pregnancy obesity and infant mortality.