An increased risk of pre-term birth is associated with pre-pregnancy obesity and gestational weight gain, say researchers at Boston University School of Medicine's (BUSM) Slone Epidemiology Center and Boston University School of Public Health (BUSPH).
The Black Women's Health Study was conducted on African American women. It currently appears on-line in Epidemiology.
A baby born at less than 37 weeks of gestation is considered preterm.
To reach the conclusion, the BUSM researchers used data from the Slone Epidemiology Center's Black Women's Health Study. They compared mothers of more than 1,000 infants born three or more weeks early with mothers of more than 7,000 full-term infants.
They examined two types of preterm birth: that indicated for medical reasons (medically-indicated) and that occurring for no known reason (spontaneous).
The researchers found that obesity increased the risk of medically-indicated preterm birth and very early spontaneous preterm birth, and that underweight increased risk of both preterm birth subtypes. Among obese women, gestational weight gain within the range recommended by the 2009 Institute of Medicine (IOM) report was optimal in reducing risk of preterm birth.
"Our data suggest that it is especially important for obese women to adhere to the IOM guidelines for pregnancy weight gain to reduce their risk of preterm birth," said lead author Lauren A. ise, ScD, an associate professor of epidemiology at Boston University School of Public Health and a senior epidemiologist at the Slone Epidemiology Center.