Obstetrics and Gynecology, New York: A new study confirms that weight gain during pregnancy affects the risk of spontaneous pretern birth and suggests that both race and a history of preterm birth seem to influence the association. Prior studies have suggested that low and high weight gain during pregnancy raise the likelihood that a woman will deliver prematurely.

Ethnicity and birth history are known to influence the risk of preterm birth, but it was unclear whether these factors interact with maternal weight gain. Dr. Naomi E. Stotland, from San Francisco General Hospital and colleagues addressed this issue by analysing data from 15,101 singleton births. Prior to pregnancy, the women had normal weight, with BMIs no greater than 25. The mothers were divided into three groups based on thedegree of weight gain during pregnancy: low, normal, and high. Overall, low weight gain increased the odds of spontaneous preterm birth by 2.5-fold, Stotland and colleagues report. Low weight gain was a risk factor for pretern birth in all ethnic groups, but the association in Asians fell short of statistical significance. A high weight gain was also linked to spontaneous preterm birth. In Asians, there was evidence that high weight gain may actually reduce the risk of preterm birth. However, the 50 percent reduction in risk seen was not statistically significant.

"The robust association between low gain and spontaneous preterm birth suggests that, in this era of appropriate concern over an obesity epidemic, we must strike a careful balance between excessive and inadequate weight gain," the research team states."Our findings suggest that future research exploring risk factors or mechanisms for spontaneous preterm birth should consider both maternal race or ethnicity and previous preterm birth status, because these variables modify the relationship between gestational weight gain and spontaneous preterm birth."