17: Residence in the US a risk factor for preterm birth


      It is not known whether preterm birth is predominantly related to genetic or environmental factors. To address this question the objective of this study was to determine the risk of preterm birth in relation to duration of residence in the U.S. among Hispanics.

      Study Design

      Risk of preterm birth in relation to duration of residence in the U.S. was evaluated in a population based study of 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.


      The prevalence of preterm birth was 4.0% (18/447) among women residing =10 years and was 9.5% (85/897) among Hispanic women born in the U.S. (p=0.002). Comparing to women residing in the U.S. for =10 years and women born in the U.S. (age adjusted OR [95% CI]: 2.1 [1.1-4.4]; p=0.043 and 3.1 [1.5-6.2]; p=0.002, respectively). Adjustment for: age, BMI, education, marital status, income, prior smoking and current cotinine concentrations, diabetes, hypertension, preferred language at home and if all births occurred while residing in the U.S. did not have a material effect (fully adjusted OR [95% CI]: 2.1 [1.1-4.2]; p=0.031 and 3.5 [1.4-8.9]; p=0.008, respectively). There were no significant differences in the age at the first live birth between the groups (p=0.2). Almost 50% of the preterm births among Hispanic can be attributed to being born in the U.S (Attributable Fraction for the Population: 47.5%).


      Duration of stay in the U.S. is associated with increasing risk of preterm birth for Hispanic women. This finding supports a hypothesis that the preterm birth, at least in part, is related to environmental, potentially preventable, factors.