200 Association Between Maternal Region of Origin and Birth and Obstetric Anal Sphincter Injury, by Length of Residence: A Nation-Wide Cohort Study

Introduction: Obstetric anal sphincter injury (OASI) is a severe obstetric complication, associated with long-term urogenital pain and dysfunction. Few studies have explored association between migration related characteristics and OASI. Our aim was to examine the association between maternal region of origin and birth, and OASI, by length of residence in Norway and paternal birthplace. Methods: This is a population-based cohort study on data from the Medical Birth Registry of Norway, including all primiparous women with a vaginal livebirth of a singleton cephalic foetus between 2008 and 2017 (n=188 658). Multivariable logistic regression was used to estimate the association between maternal region of origin and birth, with OASI, stratified on length of residence and paternal birthplace, presented as adjusted odds ratios (aORs) with 95% confidence intervals (CI). Results: We identified 6 373 cases (3.4%) of OASI. Compared to Norwegian women, proportion of OASI was highest among South Asian women (6.2%; aOR 2.46, 95% CI 2.05-2.95), followed by Southeast/East Asian/Pacific (5.7%; aOR 1.88, 95% CI 1.64-2.16) and Sub-Saharan women (5.2%; aOR 1.95, 95% CI 1.63-2.34). Among women born in the same region, we observed stronger risk estimates for OASI in newly arrived migrants compared to those with longer residencies with the highest risk among newly arrived South Asian women (aOR 3.40, 95% CI 2.55-4.53). Having a foreign-born partner increased the odds of OASI independent of maternal region of origin. Conclusion: The risk of OASI differed by maternal birthplace and region of origin. Primiparous women originating from Asian regions and Sub-Saharan Africa were more likely to sustain an OASI compared to Norwegian-born women. Newly arrived migrants from Asian and African regions including the Middle East and those with a foreign-born partner were at elevated risk. Subgroups of migrants may benefit from special attention in labour to reduce morbidity and achieve equitable care.