Full length article The effect of polyhydramnios on the success of trial of labor after cesarean delivery (TOLAC): A retrospective cohort Yossi Bart a,b, *, Aya Mohr-Sasson a,b , Shali Mazaki-Tovi a,b , Anat Kalter a,b , Moran Shapira a,b , Eyal Sivan a,b , Israel Hendler a,b a Department of Obstetrics and Gynecology, Sheba Medical Center, Tel-Hashomer, Israel b Sackler School of Medicine, Tel Aviv University, Tel Aviv, Israel A R T I C L E I N F O Article history: Received 2 May 2020 Received in revised form 29 July 2020 Accepted 21 August 2020 Keywords: Amniotic fluid index Cesarean delivery Polyhydramnios Trial of labor after cesarean delivery A B S T R A C T 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. © 2020 Elsevier B.V. All rights reserved. Introduction The overall incidence of polyhydramnios ranges in various studies from 0.5 to 2% [1,2]. It is defined by either a single deepest pocket (SDP) >80 mm or amniotic fluid index (AFI) >240 mm [3]. Polyhydramnios may be a sign of underlying maternal complications such as gestational diabetes or fetal congenital anomalies such as trachea-esophageal fistula as well as isolated or idiopathic [4,5]. The increased amount of amniotic fluid is associated with an elevated incidence of maternal and fetal morbidity and mortality, including preterm birth, macrosomia, placental abruption, umbili- cal cord prolapse, unexplained intrauterine fetal demise and postpartum uterine atony [1,5–8]. Women who are diagnosed with polyhydarmnios and had a previous cesarean delivery may opt for a trial of labor (TOLAC). The main concerns for women going for TOLAC is the success rate and the risk for uterine rupture. Overall success rate TOLAC is 60–80 % [9]. Known possible predictors for TOLAC success include maternal age and BMI prior vaginal deliveries, macrosomia, prior indication for cesarean delivery, multiple gestation and postterm pregnancy [10–15]. Risk factors for uterine rupture include number of prior cesarean deliveries, prior vaginal delivery and labor induction or augmentation [16–19]. The influence of polyhydramnios on TOLAC success rate or on the risk for uterine rupture has not been sufficiently studied. Few studies showed increased risk for cesarean delivery (CD) in laboring women [8,20]. However, a number of studies had inconsistent results [1,5,21]. One study showed lower rates of successful TOLAC after a cesarean delivery, although women with diabetes mellitus were excluded and the study group was small [8]. * Corresponding author at: Department of Obstetrics and Gynecology, Sheba Medical Center, Tel-Hashomer, Ramat Gan, 52621, Israel. E-mail address: yossef.bart@sheba.health.gov.il (Y. Bart). https://doi.org/10.1016/j.ejogrb.2020.08.017 0301-2115/© 2020 Elsevier B.V. All rights reserved. European Journal of Obstetrics & Gynecology and Reproductive Biology 253 (2020) 187–190 Contents lists available at ScienceDirect European Journal of Obstetrics & Gynecology and Reproductive Biology journal homepage: www.elsevier.com/locate/ejogrb