The "healthy immigrant paradox" in perinatal health: evidence from differences between natives and migrants in birth weight in Spain and Ecuador

Héctor Cebolla-Boado, Universidad Nacional de Educación a Distancia (UNED)
Leire Salazar, Universidad Nacional de Educación a Distancia (UNED)

This paper explores differences in perinatal inequality between migrant- and native- origin newborns in Spain and, more specifically, differences in birth weight. Previous literature has shown that, in line with the "healthy immigrant paradox", the children of immigrant mothers tend to have a lower risk of low birth weight. Using the universe of births in Spain and Ecuador in 2013, we compare three groups of newborns: those from Spanish-born mothers, from Ecuadorian-born mothers settled in Spain, and from Ecuadorian mothers living in Ecuador. The comparison of migrants to Spain with non-migrants in the country of origin provides an interesting scenario to test the validity of the existence of positive selection in the migrant population. Our paper does not only confirm that the epidemiological regularity of healthier babies among migrants in advanced economies, namely an advantage of immigrant-origin babies in terms of avoiding low birth weight, also applies to Spain. By using quintile regression, it confirms the weight advantage throughout the whole distribution of weight. In the extreme, when the baby’s weight is above 4,000 grams, a threshold that is associated with increased health risks, migrant-origin babies weigh about 80 grams more than native-origin ones and over 250 grams more than newborns in Ecuador. We therefore contribute to the literature by confirming the consistently higher birth weight enjoyed by the children of migrant mothers in a country such as Spain, where immigration is a recent phenomenon and access to quality healthcare is universal and free of charge. The comparison between babies from Ecuadorian mothers born in Spain and Ecuador also provides evidence consistent with the existence of positive selection among migrants. Last, the use of quantile regression has revealed that the higher average weight of newly born babies from immigrant mothers becomes a disadvantage at the highest end of the distribution.