Background: Studies have shown that immigrants residing in Spain have lower risks of delivering low birthweight (LBW) and preterm babies despite their socioeconomic disadvantages (the healthy migrant paradox). However, less is known about other important perinatal outcomes derived from birth weight and gestational age such as macrosomia and post-term birth. This paper aims to compare the main indicators related to birth weight and gestational age (LBW, macrosomia, preterm and post-term) for immigrants and Spaniards. Methods: Cross-sectional study based on the Spanish vital statistics for years 2009-2011. Multinomial regression models were performed to obtain crude and adjusted ORs and their 95% CIs. Results: After adjusting for known confounders, compared with Spaniards, most immigrant groups show lower or not significantly different risks of delivering LBW (OR between 0.65 and 0.87) or, more exceptionally, preterm babies (between 0.75 and 0.93). However, most of them also show higher risks of delivering macrosomic (OR between 1.21 and 2.58) and post-term babies (OR between 1.11 and 1.50). Mothers from sub-Saharan Africa show a higher risk in all perinatal outcomes studied. Conclusions: The immigrant health paradox should be carefully assessed in comprehensive terms. Together with a predominantly lower risk of LBW, most immigrants have a higher risk of macrosomia, post-term and preterm births. These results have policy-making implications since studying the right tail of the birth weight and gestational age distributions implies considering a different set of risk factors.

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Confounding Factors (Epidemiology) health disparity Health Status Disparities human epidemiology Infant, Premature Cross-Sectional Studies cross-sectional study migrant Humans Infant, Newborn Emigrants and Immigrants Spain female risk factor Risk Factors newborn pregnancy Infant, Low Birth Weight Retrospective Studies low birth weight Infant, Small for Gestational Age adult small for date infant prematurity social class retrospective study Fetal Macrosomia Vital Statistics gestational age