Study finds residence in US a risk factor for preterm birth

In a study to be presented today at the Society for Maternal-Fetal Medicine's annual meeting, The Pregnancy Meeting, in Dallas, Texas, researchers will report findings that indicate that duration of stay in the United States is associated with increased risk of preterm birth for Hispanic women.

"It is uncertain how important environmental factors are in predisposition to preterm birth," said Radek Bukowski, MD, PhD, with the University of Texas Medical Branch, Department of Obstetrics and Gynecology, in Galveston, Texas, and one of the study's authors. "To address this question, the objective of the study was to determine the risk of preterm birth in relation to duration of residence in the U.S. among Hispanic women."

For the study, entitled Residence in the U.S. a Risk Factor for Preterm Birth, Bukowski and his colleague, Julian Robinson, MD, with Brigham and Women's Hospital, Obstetrics and Gynecology, in Boston, Mass., studied 2,141 Hispanic women with a prior live birth who participated in the National Health and Nutrition Examination Survey (1999-2006), a probability sample of the U.S. population. They found that women living in the U.S. for less than 10 years had a 3.4 percent frequency of preterm birth and women living in the U.S. for 10 or more years had twice the risk of preterm birth and a 7.4 percent frequency of preterm birth. Furthermore, women born in the U.S. had a 10 percent frequency of preterm birth and three-fold risk of preterm birth. The risk of preterm birth did not appear to be related to a number of preterm birth risk factors investigated, but because it was acquired during residence in the U.S., it is potentially modifiable.

The findings support the hypothesis that preterm birth is, at least in part, related to environmental, potentially preventable, factors. It remains unclear what specific environmental factors protect or predispose women to preterm birth.