Mediating roles of preterm birth and restricted fetal growth in the relationship between maternal education and infant mortality: A Danish population-based cohort study
Year: 2019
Type: article
Study design: Observational Study
Abstract: BACKGROUND: Socioeconomic disparities in infant mortality have persisted for decades in high-income countries and may have become stronger in some populations. Therefore, new understandings of the mechanisms that underlie socioeconomic differences in infant deaths are essential for creating and implementing health initiatives to reduce these deaths. We aimed to explore whether and the extent to which preterm birth (PTB) and small for gestational age (SGA) at birth mediate the association between maternal education and infant mortality. METHODS AND FINDINGS: We developed a population-based cohort study to include all 1,994,618 live singletons born in Denmark in 1981-2015. Infants were followed from birth until death, emigration, or the day before the first birthday, whichever came first. Maternal education at childbirth was categorized as low, medium, or high. An inverse probability weighting of marginal structural models was used to estimate the controlled direct effect (CDE) of maternal education on offspring infant mortality, further split into neonatal (0-27 days) and postneonatal (28-364 days) deaths, and portion eliminated (PE) by eliminating mediation by PTB and SGA. The proportion eliminated by eliminating mediation by PTB and SGA was reported if the mortality rate ratios (MRRs) of CDE and PE were in the same direction. The MRRs between maternal education and infant mortality were 1.63 (95% CI 1.48-1.80, P < 0.001) and 1.19 (95% CI 1.08-1.31, P < 0.001) for low and medium versus high education, respectively. The estimated proportions of these total associations eliminated by reducing PTB and SGA together were 55% (MRRPE = 1.27, 95% CI 1.15-1.40, P < 0.001) for low and 60% (MRRPE = 1.11, 95% CI 1.01-1.22, P = 0.037) for medium versus high education. The proportions eliminated by eliminating PTB and SGA separately were, respectively, 46% and 11% for low education (versus high education) and 48% and 13% for medium education (versus high education). PTB and SGA together contributed more to the association of maternal educational disparities with neonatal mortality (proportion eliminated: 75%-81%) than with postneonatal mortality (proportion eliminated: 21%-23%). Limitations of the study include the untestable assumption of no unmeasured confounders for the causal mediation analysis, and the limited generalizability of the findings to other countries with varying disparities in access and quality of perinatal healthcare. CONCLUSIONS: PTB and SGA may play substantial roles in the relationship between low maternal education and infant mortality, especially for neonatal mortality. The mediating role of PTB appeared to be much stronger than that of SGA. Public health strategies aimed at reducing neonatal mortality in high-income countries may need to address socially related prenatal risk factors of PTB and impaired fetal growth. The substantial association of maternal education with postneonatal mortality not accounted for by PTB or SGA could reflect unaddressed educational disparities in infant care or other factors.
Source: PLoS Medicine
Institutions: University of California, Los Angeles, Aarhus University, University College London, Yale University, University of California, San Francisco, National University of Singapore, Shanghai Jiao Tong University, XinHua Hospital, Duke-NUS Medical School, Karolinska University Hospital, Karolinska Institutet, Fudan University
Language: English
Subfield: General Health Professions
Field: Health Professions
Domain: Health Sciences
Open Access status: gold
Estimated APC paid: $3,000
Funders: Nordic Cancer Union, National Natural Science Foundation of China, Fudan University, Lundbeckfonden, Karen Elise Jensens Fond, Novo Nordisk, Danmarks Frie Forskningsfond, Novo Nordisk Fonden, H. Lundbeck A/S, National Institutes of Health, Medical Research Council, National Institute of Environmental Health Sciences, National Institute of Child Health and Human Development, U.S. National Library of Medicine, National Center for Advancing Translational Sciences, California Center for Population Research, University of California, Los Angeles, Eunice Kennedy Shriver National Institute of Child Health and Human Development
Awards: HOD: Handling missing data and time-varying confounding in causal inference for observational event history data, G1412828664, G2507980080, HOD: Handling missing data and time-varying confounding in causal inference for observational event history data, G3253195855, G4521338123, G5654657460, G5860759440, G5979852851, California Center for Population Research (CCPR) at UCLA, G692852242, Elucidating the Role of the Genetic and Environmental Determinants of Preterm Birth Using Integrative Computational Approaches, The impact of natural experiments on child obesity: A systems science approach, G8869203862, Revealing environmental chemical exposome in a diverse prenatal population and relationships to maternal and perinatal health (REVEAL), UCLA Clinical and Translational Science Institute
OpenAlex ID: W2953201948