Maternal Asian ethnicity and the risk of anal sphincter injury

Abstract

Objective: To examine associations between maternal Asian ethnicity (South Asian and South East/East Asian) and anal sphincter injury.

Design: Retrospective cross-sectional study, comparing outcomes for Asian women with those of Australian and New Zealand women.

Setting: A large metropolitan maternity service in Victoria, Australia.

Population: Australian/New Zealand, South Asian and South East/East Asian women who had a singleton vaginal birth from 2006 to 2012.

Methods: The relation between maternal ethnicity and anal sphincter injury was assessed by logistic regression, adjusting for potential confounders.

Main outcome measures: Anal sphincter injury was defined as a third or fourth degree tear (with or without episiotomy).

Results: Among 32,653 vaginal births there was a significant difference in the rate of anal sphincter injury by maternal region of birth (p < 0.001). After adjustment for confounders, nulliparous women born in South Asian and South East/East Asia were 2.6 (95% confidence interval 2.2-3.3; p < 0.001) and 2.1 (95% confidence interval 1.7-2.5; p < 0.001) times more likely to sustain an anal sphincter injury than Australian/New Zealand women, respectively. Parous women born in South Asian and South East/East Asia were 2.4 (95% confidence interval 1.8-3.2; p < 0.001) and 2.0 (95% confidence interval 1.5-2.7; p < 0.001) times more likely to sustain an anal sphincter injury than Australian/New Zealand women, respectively.

Conclusion: There are ethnic differences in the rates of anal sphincter injury not fully explained by known risk factors for such trauma. This may have implications for care provision.

Keywords: Maternal ethnicity; anal sphincter injury; episiotomy; perineum; risk factors.

© 2014 Nordic Federation of Societies of Obstetrics and Gynecology.