A new study by researchers at the University of South Florida says maternal obesity plays differing role in causing infant mortality in blacks and whites.
The team found that while maternal obesity appears to have no impact on the early survival of infants born to white women, the situation is different for black women.
Their study showed that babies born to obese black mothers had a higher risk of death in the first 27 days following birth than newborns of obese white mothers.
Furthermore, this black disadvantage in neonatal infant mortality widened with an increase in the body mass index (BMI).
"Even if the infant of an obese black woman survives pregnancy, labor and delivery, that baby is at greater risk of dying than a baby born to an obese white woman," said the study's lead author Hamisu Salihu, MD, PhD, associate professor of epidemiology at the USF College of Public Health.
For the study, researchers analyzed more than 1.4 million births recorded from Missouri's vital records database, covering the period 1978 through 1997. The database associated black and white mother-infant pairs.
The researchers found that among all women, the likelihood of neonatal death (up to 27 days following death) and early neonatal death (up to six days following death) was 20 percent greater than for non-obese women.
Further analysis showed that the higher risk of neonatal deaths among newborns of obese mothers was confined to blacks only.
The rate of neonatal deaths increased significantly with rising BMIs of black women (ranging from 50 to 100-percent increments).
However, the offspring of obese white mothers, regardless of the severity of maternal obesity, had no greater risk of neonatal death than the newborns of non-obese women.
Researchers found that the black-white disparity in infant mortality persisted even when they adjusted for certain obesity-associated medical complications more prevalent in black women - high blood pressure, diabetes and preeclampsia.
"This further confirms our findings that high BMI is an independent risk factor for neonatal mortality among blacks but not whites," Dr. Salihu said.
The researchers also controlled for the amount of prenatal care received since another possible explanation for the black-white disparity may be that obese white women have better access to prenatal care than black women.
Their results suggested otherwise, but Dr. Salihu has warned that more research is required.
"We cannot dismiss access to care as a factor because the quantity of prenatal care does not take into account the quality of care received," he said.
Dr. Salihu has suggested that differences in the way fat is distributed in white and black women might play a role in their newborns' survival.
"If we can understand more about the potential association between fat distribution in mothers and likelihood of death in their babies, we might have an avenue for prevention and narrowing the persistent black-white gap in infant mortality," he said.
The study is published in the June 2008 issue of the journal Obstetrics and Gynecology.