Prenatal care and risk of preterm birth among foreign and US-born mothers in Michigan.

Studies among ethnic minorities suggest that prenatal care (PNC) may be less protective against preterm birth (PTB) among foreign-born relative to US-born mothers. We assessed relations between nativity, PNC inadequacy, and PTB risk over 17 years in one US state. Adjusted multivariable models were fit to assess the potential interaction between nativity and PNC inadequacy as a determinant of PTB. Additionally, we calculated predicted probabilities of PTB by PNC inadequacy, stratified by nativity. In adjusted models of PTB, there was a significant interaction (P (interaction) < 0.01) between nativity and PNC inadequacy. US-born mothers who did not use PNC adequately had 2.9% higher predicted probability of PTB than adequate users, which compares to 1.9% difference among foreign-born mothers. While adequate PNC use was lower among foreign-born compared to native born mothers, when accessed, PNC use may be less protective against PTB among foreign-born mothers relative to native-born mothers. Differences in cultural health traditions during pregnancy, or baseline health status between foreign and native-born mothers may mediate our findings.