Figuring out the reasons
The leading reasons for that higher risk appear to be high blood pressure and placental disorders, the researchers suggested.
"We've known for some time that obese women are more likely to have stillbirths, but this is one of the first and most comprehensive efforts to figure out why," study author Lisa Bodnar, an associate professor in the department of epidemiology at the University of Pittsburgh Graduate School of Public Health, said in a university news release.
However, because of the study's design, the authors could only show an association between obesity and stillbirth; they couldn't prove a cause-and-effect relationship.
The researchers reviewed information from more than 650 stillbirths at Magee-Womens Hospital of University of Pittsburgh Medical Centre, between 2003 and 2010. For the study, stillbirths were defined as cases that had reached at least 16 weeks' gestation and there was no evidence of life after delivery.
The rate of stillbirths was just under eight per 1,000 births for lean women. The rate jumped to 17 per 1,000 births for severely obese women, the study revealed.
Certain complications were more likely to occur in obese women, the investigators found. These complications included high blood pressure, placental diseases or disorders, foetal abnormalities, and umbilical cord abnormalities, the study said.
"Our hope is that this work can be used to better counsel women on the importance of a healthy pre-pregnancy weight, and monitor them for complications during pregnancy that may threaten the survival of their foetuses," Bodnar said.
"This study also could be used to guide prevention efforts at a societal level," Bodnar contended. "If we can reduce pre-pregnancy obesity by even a small amount, through environmental or policy changes, we could significantly reduce the burden of stillbirth."
The study was released online, and is to be published in the print issue of the American Journal of Clinical Nutrition.
Doctors should monitor pregnant obese patients for complications so they can quickly treat conditions such as high blood pressure and, hopefully, reduce the risk of stillbirth, study senior author Dr Hyagriv Simhan, professor and chief of the division of maternal-foetal medicine and medical director of obstetrical services at Magee, said in the news release.
"However, we'd like to see these women before they even become pregnant.
When a doctor has an obese patient who is considering pregnancy, she should be referred to a maternal-foetal medicine specialist who can counsel her on the benefits of losing weight before pregnancy, as well as safe approaches to weight loss," Simhan said.
There are 3.2 million stillbirths worldwide each year, and the United States has one of the highest rates of stillbirth among high-income countries, the researchers said.
Image: Lady with measuring tape from iStock