Induction of labor and risk of third- and fourth-degree perineal tears

OBJECTIVES: The rate of induction of labor (IOL) at term has been increasing over the years. Our objective was to evaluate the risk of third- and fourth-degree perineal tears associated with term induction of labor. This section of the Journal of Obstetrics and Gynaecology Canada contains the oral, poster, and video abstracts that were to be presented at the SOGC's 76th Annual Clinical and Scientific Conference (ACSC) to have been held from June 9 to 12, 2020, in Ottawa, Ontario, and included as part of the conference proceedings. Due to the global spread of COVID-19 and the increasing health and safety measures being put in place by all levels of government, the SOGC has cancelled the 2020 ACSC. As a result, abstract participants will instead be submitting their presentations with voice-over narration. The presentations will then be posted on the 2020 ACSC Abstract Program page of sogc.org. We invite you to visit this page in early June to participate in the 2020 Abstract Program and to learn about the exciting research being conducted and innovations emerging in the field of obstetrics and gynaecology. There will also be an opportunity to ask authors questions. I would like to thank the entire Abstract Program Committee, the reviewers, and the participants, without whom the ACSC Abstract Program would not be possible. Dr. Alain Gagnon Chair, Abstract Program Committee METHODS: We conducted a population-based, retrospective cohort study using the United States' Nationwide Inpatient Sample to evaluate the risk of third- and fourth-degree perineal tears in women who underwent IOL at term between 2005 and 2014. We included all term livebirths and excluded, preterm births, previous cesarean deliveries, multifetal gestations, and non-cephalic presentation. Women who underwent an IOL at term were identified using ICD-9 coding. Patient characteristics were compared between those women being induced at term with those who weren't, and logistic regression analysis were carried out to estimate the adjusted effect of IOL at term with risk of 3rd and 4th perineal tears. RESULTS: Among 5,982,945 eligible live births, 1,035,003 (17.3%) underwent an IOL at term, increasing from 15.7% to 18.5%. Women with an IOL were more likely to be older, Caucasian, and with comorbid illnesses. Compared with women who did not undergo an IOL, women in the IOL group had lower risk of cesarean deliveries, 0.89 (0.88–0.89), 2nd degree tears, 0.89 (0.89–0.90), 3rd degree tears, OR 0.81 (95% CI 0.79–0.82) and 4th degree tears, OR 0.84 (95% CI 0.82–0.87). CONCLUSIONS: Induction of labor at term results in significantly lower risk of third- and fourth-degree perineal tears among all deliveries as well as among women with vaginal deliveries.