The effect of polyhydramnios on the success of trial of labor after cesarean delivery (TOLAC): A retrospective cohort

Objective: Prediction of success of trial of labor after cesarean delivery (TOLAC) is of major importance. We investigated the impact of polyhydramnios on the success rate of TOLAC. Study design: A retrospective cohort study of all women with singleton pregnancies >= 34th weeks of gestation who underwent TOLAC after one previous cesarean delivery, between 2011 and 2016 in a single tertiary care center. Polyhydramnios was defined as amniotic fluid index >= 240 mm. Primary outcome was defined as the rate of successful TOLAC. Results: 31,245 women gave birth during the study period, of them 1637 (5.3 %) women underwent TOLAC and met inclusion criteria. 39 (2.4 %) women with polyhydramnios were compared to a control group of 1598 (97.6 %) women with amniotic fluid index < 240 mm. Polyhydramnios significantly reduced the rate of successful TOLAC: 69.2 % (27/39) in the study group compared to 85.8 % (1371/1598) in the control group (P = 0.009). In a subgroup analysis based on amniotic fluid index, women with AFI > 270 mm had substantially lower TOLAC success rate [9/19 (47.4 %) vs 18/20 (90 %); P = 0.006]. There was no difference in the rate of uterine rupture between the groups (0/39 (o%) vs 9/1598 (0.56 %); P = 0.64). Logistic regression analysis revealed that polyhydramnios remained significantly associated with higher rates of cesarean delivery [OR 3.09 (95 % CI, 1.37-6.98)] after adjustment for confounding factors. Conclusion: Polyhydramnios was associated with significantly reduced TOLAC success rate with no statistical difference in the rate of uterine rupture. This information should be considered in physician counseling. (C) 2020 Elsevier B.V. All rights reserved.