By Robert Preidt
But even though the researchers found that pre-pregnancy obesity was related to worse outcomes for infants, it's important to note that the study wasn't designed to prove a cause-and-effect relationship.
Still, the study's lead author, Eugene Declercq of Boston University School of Public Health, said, "There is a need for more open, honest discussions about avoiding the possible risks of maternal obesity on infant health."
For the study, researchers reviewed data from more than 6 million newborns. The babies were born in 38 states between 2012 and 2013.
Infants born to obese women were twice as likely to die from preterm birth-related causes than those born to normal-weight women, the investigators found.
Even if obese women adhered to weight-gain guidelines during pregnancy, it had little effect on infant death risk, the study authors said.
The study highlights the need to address obesity before pregnancy, and for more research into what increases the risk of death in infants born to obese women, said Declercq, a professor of community health sciences at Boston University School of Public Health.
"The findings suggest that primary care clinicians, ob-gyns and midwives need to have conversations about weight as part of well-woman care, and when women are contemplating getting pregnant," he said in a university news release.
The obesity rate among American women aged 20 to 39 years is about 32 percent, the researchers said in the news release.
The findings were published online recently in the journal Obstetrics and Gynecology.