449 Fetal head station at second stage dystocia- does it predict subsequent TOLAC success rate?

Abstract

The factors associated with successful trial of labor after cesarean (TOLAC) among women with prior cesarean delivery (CD) for second-stage dystocia remain largely unestablished. We aimed to determine whether fetal head station at the index CD predicts the success rate of subsequent trial of labor among primiparous women. A retrospective cohort study conducted at two tertiary, university affiliated medical centers, including all primiparous women with subsequent delivery after CD for second-stage dystocia during 2009-2019. Overall, 481 primiparous women with prior CD for second-stage dystocia, had a subsequent delivery during study period. Of them, 171 (35.6%) women had an elective repeat CD and 310 (64.4%) attempted a TOLAC. Those undergoing TOLAC were younger (P<0.001), with lower rates of hypertensive disorders (P=0.005) and gestational diabetes (P=0.003) at the subsequent pregnancy. Of those undergoing TOLAC (n=310), 222 (71.6%) successfully delivered vaginally. The rate of successful TOLAC was significantly higher in those with fetal head station below the ischial spines at the index CD as compared to those with higher head station (79.0% vs. 60.5%, P<0.001). The proportion of infants weighing >3,500 grams in the subsequent delivery was lower in those with successful compared with failed TOLAC (29.7% vs. 43.2%, OR [95% CI]: 0.56 (0.33-0.93), P=0.03). In a multivariable analysis, lower fetal head station at the index CD was the only independent factor associated with TOLAC success (aOR [95% CI]: 2.38 (1.43, 3.96), P=0.001). Lower fetal head station at the index CD for second-stage dystocia was independently associated with higher VBAC rate, with an overall acceptable success rate. These findings should improve patient counseling and reassure those who wish to delivery vaginally after prior second-stage arrest.