Induction of Labor and Risk of Third- and Fourth-Degree Perineal Tears [18P

Abstract

INTRODUCTION: 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. 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). CONCLUSION: 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.