Social Inequalities in Birthweight in Times of Crisis. A Population-Level Analysis of Social Inequalities in Birthweight before and during Covid-19 Pandemic Using Data from 11 Countries.

Moritz Oberndorfer , University of Helsinki
Eugenio Paglino, University of Helsinki
Hanna Remes, University of Helsinki
Juha M O Luukkonen, University of Helsinki
Pekka Martikainen, University of Helsinki

Crises like the COVID-19 pandemic hit populations with new potentially harmful and protective exposures that may be distributed unequally in a population. Counterintuitively, even stark social inequalities in the distribution of crisis-related exposures may not lead to an observed increase in social inequalities in perinatal health. This is because crises-related exposures may change the composition of live births through selection in utero and/or selective fertility. To analyse how social inequalities in birthweight change during crises, we used individual-level data from 5 countries (Brazil, Ecuador, Finland, Spain, United States) and 6 more until June 2026 (Austria, Denmark, Netherlands, Scotland, South Australia, Sweden) covering births from 2015 to 2021. Births were nested within social strata consisting of the combination of parental socioeconomic circumstances, maternal age, maternal partnership status, and first-time/already mother. We used Bayesian linear multilevel modelling. Results suggest between-country differences in grand mean birthweight of up to 400g among unexposed live births. Within-country differences in birthweight between social strata were similarly large but their extent varied across countries. Changes in mean birthweights differed by up to 40g between strata within countries. In Spain, babies conceived during the pandemic had smaller between- and within-strata variation in birthweight compared to unexposed cohorts. we find weak evidence for changes in social inequalities in birthweight across countries during the pandemic. A lack of changes in social inequalities in birthweight may be explained by the simultaneous effects of crisis-related exposures widening inequalities and selection in utero and at conception decreasing variation in birthweight between social strata.

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 Presented in Session 35. International and Cross-Country Health Comparisons