Vaginal birth after Cesarean delivery: predicting success, risks of failure.

OBJECTIVES: To identify predictors of successful trial of labor in women after one low transverse Cesarean delivery and no prior deliveries, and to assess perinatal morbidity associated with a failed vaginal birth after Cesarean delivery (VBAC).

METHODS: Retrospective chart review of women with one low transverse Cesarean delivery in their first pregnancy who delivered their next pregnancy at our institution. Clinical characteristics and intrapartum data were reviewed to identify predictors of successful VBAC. Perinatal outcomes were reviewed to assess morbidity associated with VBAC attempt and failed VBAC.

RESULTS: Of 768 women studied, 522 (68%) attempted VBAC and 344 (66%) of these were successful. Uterine rupture occurred in 0.8% of the VBAC group. On initial examination, women with cervical dilation >1 cm, effacement > 50% and station lower than -1 were more likely to deliver vaginally. Women with successful VBAC had more spontaneous labor (85.2 vs. 76.4%, p=0.02) and less oxytocin use (49.7 vs. 70.8%, p < 0.0001). There were no differences in outcomes between failed and successful VBAC, except more frequent 1-min Apgar scores < 5 (10.1 vs. 4.1%, p=0.01) and increased endometritis (9.6 vs. 2%, p=0.0002) with failed VBAC. Compared with elective repeat Cesarean delivery, VBAC attempt was associated with amnionitis (5.9 vs. 0%, p < 0.0001) and low 1- and 5-min Apgar scores (6.1 vs. 2.4%, p=0.03 and 2.3 vs. 0%, p=0.01, respectively), but not endometritis, admission to a neonatal intensive care unit (NICU), ventilation, intraventricular hemorrhage (IVH) or seizures. Failed VBAC had more amnionitis (7.3 vs. 0%, p < 0.0001), postpartum fever (11.2 vs. 2.4%, p=0.0003) and endometritis (9.6 vs. 2.0, p=0.0007) than elective repeat Cesarean delivery and was associated with low 1- and 5-min Apgar scores (10.1 vs 2.4%, p < 0.001 and 2.8 vs. 0%, p=0.01, respectively), but not NICU admission, ventilation, IVH or seizures.

CONCLUSIONS: Favorable initial pelvic examination, spontaneous labor and a lack of oxytocin use are associated with successful VBAC in women with a single prior low transverse Cesarean delivery and no prior vaginal deliveries. While attempted VBAC and failed VBAC have more maternal infectious morbidity and lower Apgar scores, infant outcomes are similar to those of elective repeat Cesarean delivery.