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Maternal Ethnicity and the Risk of Obstetrical Anal Sphincter Injury: A Retrospective Cohort Study

  • Mohammad Albar
    Affiliations
    Department of Obstetrics and Gynecology, University of Toronto, Toronto, ON
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  • Amir Aviram
    Affiliations
    Department of Obstetrics and Gynecology, University of Toronto, Toronto, ON

    Division of Maternal-Fetal Medicine, Department of Obstetrics and Gynecology, Sunnybrook Health Sciences Centre, University of Toronto, Toronto, ON
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  • Saja Anabusi
    Affiliations
    Division of Maternal-Fetal Medicine, Department of Obstetrics and Gynecology, Sunnybrook Health Sciences Centre, University of Toronto, Toronto, ON
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  • Tianhua Huang
    Affiliations
    Department of Obstetrics and Gynecology, University of Toronto, Toronto, ON

    Genetics Program, North York General Hospital, Toronto, ON
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  • Modupe Tunde-Byass
    Affiliations
    Department of Obstetrics and Gynecology, University of Toronto, Toronto, ON

    Maternal-Fetal Medicine Unit, Department of Obstetrics and Gynecology, North York General Hospital, University of Toronto, Toronto, ON
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  • Elad Mei-Dan
    Correspondence
    Corresponding author: Elad Mei-Dan,
    Affiliations
    Department of Obstetrics and Gynecology, University of Toronto, Toronto, ON

    Division of Maternal-Fetal Medicine, Department of Obstetrics and Gynecology, Sunnybrook Health Sciences Centre, University of Toronto, Toronto, ON

    Maternal-Fetal Medicine Unit, Department of Obstetrics and Gynecology, North York General Hospital, University of Toronto, Toronto, ON
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Published:September 07, 2020DOI:https://doi.org/10.1016/j.jogc.2020.08.016

      ABSTRACT

      Objective

      To explore the role of maternal ethnicity as a risk factor for obstetrical anal sphincter injury (OASI).

      Methods

      A retrospective cohort study of all women with singleton gestations who had a vaginal delivery at term, between January 2014 and October 2017, at a single center. OASI was defined as a third-degree perineal tear (anal sphincter complex) or a fourth-degree perineal tear (anorectal mucosa). The characteristics of women with and without OASIs were compared. Multiple logistic regression was performed to account for potential confounders, including ethnicity.

      Results

      During the study period, 11 012 women were eligible for inclusion, of whom 336 (3.1%) had an OASI; 313 (93.1%) had a third-degree tear, and 23 (6.9%) had a fourth-degree tear. Women with OASIs were characterized by younger maternal age (<35 years), Asian ethnicity, nulliparity, neonatal birth weight ≥3500 grams, midline and mediolateral episiotomy, second stage of labour lasting ≥60 minutes, and assisted vaginal delivery. After adjusting for potential confounders, Asian ethnicity remained independently associated with increased risk of OASI (adjusted odds ratio 2.07; 95% CI 1.6–2.7) whereas mediolateral episiotomy was independently associated with decreased risk of OASI (adjusted odds ratio 0.64; 95% CI 0.5–0.9).

      Conclusion

      Asian ethnicity is independently associated with increased risk of OASI. Although midline episiotomy increases the risk of OASI, mediolateral episiotomy may protect against OASI, and should be considered in high-risk patients.

      RÉSUMÉ

      Objectif

      Étudier le rôle des origines ethniques maternelles comme facteur de risque de lésion obstétricale du sphincter anal (LOSA).

      Méthodologie

      Étude de cohorte rétrospective menée dans un seul centre auprès de toutes les femmes dont la grossesse monofœtale s'est terminée à terme par un accouchement vaginal entre janvier 2014 et octobre 2017. La LOSA a été définie comme une déchirure périnéale du troisième degré (complexe sphinctérien anal) ou une déchirure périnéale du quatrième degré (muqueuse ano-rectale). Les caractéristiques des femmes avec et sans LOSA ont été comparées. Une analyse de régression logistique multiple a été effectuée pour tenir compte des facteurs de confusion potentiels, dont les origines ethniques.

      Résultats

      Pour la période à l’étude, 11 012 femmes répondaient aux critères d'inclusion. De ce nombre, 336 (3,1 %) avaient subi une LOSA; 313 (93,1 %), une déchirure du troisième degré; et 23 (6,9 %), une déchirure du quatrième degré. Les femmes ayant subi une LOSA se caractérisent par un jeune âge maternel (< 35 ans), des origines ethniques asiatiques, la nulliparité, un poids à la naissance de ≥ 3 500 grammes, une épisiotomie médiane ou médio-latérale, un deuxième stade du travail de ≥ 60 minutes et un accouchement vaginal assisté. Après ajustement des données pour tenir compte des facteurs de confusion potentiels, les origines ethniques asiatiques sont demeurées indépendamment associées à un risque accru de LOSA (rapport de cotes ajusté : 2,07; IC à 95 % : 1,6–2,7), tandis que l’épisiotomie médio-latérale est indépendamment associée à une diminution du risque de LOSA (rapport de cotes ajusté : 0,64; IC à 95 % : 0,5–0,9).

      Conclusion

      Les origines ethniques asiatiques sont indépendamment associées à un risque accru de LOSA. Bien que l’épisiotomie médiane augmente le risque de LOSA, l’épisiotomie médio-latérale peut quant à elle protéger contre les LOSA. Par conséquent, il y a lieu d'envisager l’épisiotomie médio-latérale pour les patientes à risque élevé.

      Keywords

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