Prepregnancy, obesity and gestational weight gain influence risk of preterm birth

A baby born at less than 37 weeks of gestation is considered preterm. This occurs more often among black women than white women and is a leading cause of infant morbidity and mortality in the United States. Obesity is associated with intrauterine infections, systematic inflammation, dyslipidemia, and hyperinsulinemia, all of which may increase the risk of preterm birth.

In order to investigate the relations of preterm birth with prepregnancy obesity and gestational weight gain, 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 (<32 weeks), 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 (0.4-0.6 lbs/week in the second and third trimesters) 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. Wise, ScD, an associate professor of epidemiology at Boston University School of Public Health and a senior epidemiologist at the Slone Epidemiology Center.

Funding for this study was provided by the National Cancer Institute and the Hood Foundation.