Correlatos sociales del peso al nacer. Evidencias en el contexto español

Résumé

Birth weight is considered a crucial indicator of perinatal health as it determines the likelihood of a newborn experiencing satisfactory development and growth throughout life. Adverse birth weight outcomes, namely low birth weight (<2,500 g), very low birth weight (<1,500 g), and high birth weight (>4,000 g), are associated with various risks ranging from neonatal mortality to chronic conditions such as hypertension, type 2 diabetes, metabolic syndrome, among others. Furthermore, it is also emphasized that low birth weight can have a negative impact on social, economic, and cultural well-being in adulthood. Assuming that the determinants of birth weight encompass a wide range of factors from biological, behavioral, to maternal socio-economic characteristics, this thesis aims to address some of them. Specifically, we focus on the following factors: maternal family status, maternal age at childbirth, and migratory status. Thanks to a novel dataset provided upon request by the Spanish National Statistical Office (INE), which links the 2011 census with births registered between 2011 and 2015 in the Natural Population Movement (MNP), four exercises have been conducted. In the first exercise, the effect of maternal family status on the risk of low birth weight in newborns was examined. The results provide novel evidence on the impact of marital status and household type on the birth weight of newborns born to mothers in Spain. First, contrary to what has been observed in previous studies in Spain and other countries, the study shows that living without a partner does not affect the risk of low birth weight. Second, households that include non-nuclear members are associated with low birth weight, suggesting that even in a predominantly familistic social context like Spain, the extended family does not provide complete protection against adverse birth outcomes. In the second exercise, the association between advanced maternal age and the likelihood of low or high birth weight in Spain was analyzed. The results indicate, on the one hand, that advanced maternal age (>40 years) is associated with a higher probability of giving birth to babies with low birth weight compared to mothers aged 30-34 years. On the other hand, maternal origin is a factor that may have an effect on birth outcomes. In fact, regardless of maternal age, foreign-born mothers have a higher probability of giving birth to newborns with high birth weight and a lower risk of giving birth to newborns with low birth weight compared to native Spanish mothers. Therefore, regardless of maternal age at childbirth, the importance of addressing the needs of diverse groups of mothers based on their socio-cultural and economic context is highlighted. In the third exercise, it is analyzed whether there are changes in birth weight outcomes based on the maternal age at arrival (if <16 years or >16 years) in Spain. Additionally, it investigates whether the phenomenon known as the 'epidemiological paradox' manifests in the Spanish context. The results highlight two distinct effects of the arrival cohort on birth weight outcomes. On one hand, it was observed that first-generation Latinas had a lower risk of giving birth to babies with low birth weight but experienced a higher incidence of high birth weight during the study period. On the other hand, 1.5-generation Latina women, likely stressed by increased exposure to the receiving country, exhibited adverse birth weight outcomes. The results suggest that a different level of immigrant selection and varying exposure to cultural and behavioral factors affecting society in receiving countries play a significant role in the health trajectories of immigrant women. Finally, the fourth exercise evaluates whether the duration of the mother's residence in the host country influences the relationship between maternal origin and birth weight. The results indicate that foreign-born mothers from countries with varying levels of human development were more likely to give birth to babies with high birth weight than native Spanish mothers. Given the long-term health consequences associated with high birth weight, the results underscore the need to improve prenatal care for the foreign-born population. The empirical studies in this thesis broaden our understanding of how maternal social inequalities contribute to adverse birth weight outcomes. In conclusion, it is never too early or too late to prevent health inequalities.