Impact of Socio-economic Status on Low Birthweight: Decomposing the Differences Between Natives and Immigrants in Spain.

In this population-based study, we explored the relationships between immigration, socio-economic status (SES), and perinatal outcomes. We quantified the effects of SES on birthweight disparities between native and immigrant mothers in Spain. We obtained birth and SES data from the 2011 census and administrative registers for years 2011-2015. The associations between origin, statuses, and the likelihood of low birthweight were estimated using logistic regressions. Fairlie's nonlinear extension of the Oaxaca-Blinder decomposition method was applied to identify the extent to which the differences in birthweight between groups corresponded to socio-economic composition or to rates. Our results showed that African and Latin American mothers exhibited advantage in the perinatal outcomes over native mothers [odds ratio (OR) 0.75; 95% confidence interval (CI) 0.63-0.90 and OR 0.73; 95% CI 0.65-0.82, respectively]. Decomposition analyses revealed that such advantage was not affected by the lower positions within the socio-economic structure that African and Latin American populations occupied.