Secundiparas following a failed vacuum delivery - factors associated with a successful vaginal delivery

Trial of labor after cesarean delivery (TOLAC) is challenging for both obstetricians and parturients. Identifying the appropriate candidates for TOLAC is crucial in order to minimize maternal and fetal risks. There is limited data regarding secundiparas (parity 2), attempting trial of labor following failed vacuum delivery in previous delivery (TOLAC f-VD). We aimed to study the factors associated with a successful TOLAC-fVD. A historical prospective cohort in a single university medical center throughout 2006-2019. All term, secundiparas, with a previous CD due to a f-VD were included. Obstetric characteristics of women who underwent a planned-CD were compared to those who elected a TOLAC. The latter were further analyzed to study the factors associated with successful vaginal birth after f-VD (VBAC). Among the 115 secundiparas included, 89 (77%) underwent TOLAC. Compared to women who underwent an elective CD, those who underwent TOLAC were younger by 4 years, were more likely to have conceived spontaneously and had more advanced gestation by 10 days. VBAC was achieved in 62 women (70%). Higher neonatal birthweight at P1 by increments of 500g, 400g or 300g was associated with a VBAC; OR of 4.5 (95%CI; 0.97, 21.6), 4.4 (95%CI; 1.2, 16.2) and 3.8 (95%CI; 1.2, 12.7) respectively. In contrast, higher neonatal birthweight at P2 by increments of 500g, 400g or 300g was associated with a failed TOLAC; OR of 9.7 (95%CI; 2.3, 40.0), 11.5 (95%CI; 2.8, 46.7) and 4.5 (95%CI; 1.4, 13.9), respectively. Previous posterior-occiput-persistent, previous prolonged 2nd stage, gestational week at delivery, fetal gender and gestational diabetes were not associated with a VBAC. Among secundiparas with a previous CD due to a f-VD, the absolute difference of neonatal BW was found to be a significant factor associated with achieving VBAC.