Explaining the low risk of preterm birth among arab americans in the United States: an analysis of 617451 births.

OBJECTIVES Arab Americans have a lower risk for preterm birth than white Americans. We assessed factors that may contribute to the association between ethnicity and preterm birth risk in Michigan, the state with the largest concentration of Arab Americans in the United States. Factors assessed as potential contributors to the ethnicity/preterm birth risk association were maternal age, parity, education, marital status, tobacco use, and maternal birthplace. METHODS Data were collected about all births in Michigan between 2000 and 2005. Stratified analyses, trivariate analyses, and manual stepwise logistic regression model building were used to assess potential contributors to the ethnicity/preterm birth risk association. RESULTS Arab ethnicity was associated with lower preterm birth risk compared with non-Arab white subjects in the unadjusted model. Maternal birthplace inside or outside the United States explained 0.17 of the difference in preterm birth risk between Arab ethnicity and non-Arab white mothers; ethnic differences in marital status and tobacco use explained less of the observed ethnic difference in preterm birth risk. In the final model adjusted for all explanatory variables, Arab ethnicity was no longer associated with preterm birth risk. CONCLUSIONS Maternal birthplace, marital status, and tobacco use may contribute to the preterm birth risk difference between Arab ethnicity and non-Arab white mothers. Additional work is needed to consider the mechanisms relating factors such as maternal birthplace and marital status to ethnic differences in preterm birth risk.