This is a retrospective cohort study at large academic medical center of women with a history of one previous CS undergoing an IOL for TOLAC. All women with a viable singleton term (gestational age ≥ 37 weeks 0 days) pregnancy, cephalic presentation and a cervical dilation of < 4 cm, undergoing TOLAC between January 1 2015 and October 1 2020 were identified in the hospital electronic medical record.
Women with previous classical CS, history of more than one CS, active labor, pre-labor rupture of membranes, scheduled elective CS, preterm delivery, breech presentation, multi fetal pregnancy or fetal demise were excluded from the study.
Our primary outcome was the rate of successful vaginal delivery. Secondary outcomes were total time of IOL, rates of chorioamnionitis, uterine rupture and low Apgar score (< 7).
The default mode for IOL for patients undergoing TOLAC in our hospital is AROM. This is due to the increased risk of uterine rupture with the use of prostaglandins or oxytocin in this population. In the minority of cases (less than 10%) AROM is not possible. The main reasons for this situation are a long cervical length (membranes unreachable by vaginal examination) and a high head station which may be associated with cord prolapse . In these situations, IOL was initiated with oxytocin prior to AROM, and these women were excluded from our study.
After AROM was performed, women were hospitalized to await a spontaneous onset of labor. Conservative management was limited to up to 48 h. At the onset of labor, patients were admitted to the labor ward. Women with signs suggesting chorioamnionitis such as fever, abdominal tenderness, foul-smelling vaginal discharge, leukocytosis, or maternal or fetal tachycardia were transferred immediately to the labor ward. Likewise, women with indications for immediate delivery such as preeclampsia or uncontrolled diabetes were not offered expectant management after AROM; instead, oxytocin was initiated shortly after AROM. In the reminder of cases, shared patient-physician decision making was used to decide on the timing of initiation of oxytocin.
Our protocol for oxytocin in women undergoing TOLAC recommends an initial dose of 1 miU/min. At 30-min intervals, the dose is gradually increased by increments of 1 miU/min until a maximum of 20miU/min or when a desired contraction pattern is established.
Maternal and neonatal data were retrieved using a computerized database, continuously updated and validated for admission, labor, and postpartum course.
Data collected included maternal age, maternal weight, gravidity, parity, history of previous vaginal delivery or VBAC. Data regarding current labor included gestational age (determined by early ultrasound), cervical dilatation at AROM, mode of delivery, oxytocin use, latency in minutes from AROM to oxytocin, total time of oxytocin administration and total induction time. Neonatal data included birthweight and 5-min APGAR score.
Initially, outcomes and rates of successful vaginal delivery were compered between AROM alone and AROM followed by oxytocin administration. Thereafter a second analysis was performed including only women who received oxytocin. Outcomes were compared between early (≤ 12 h) and late (> 12 h) oxytocin administration.
Continuous variables with normal distribution were compared using the Students t-test. The continuous variables without normal distribution were compared using Mann–Whitney U test. Categorical variables were compared using Pearson chi-square.
Multivariable logistic regression was conducted to identify the variables that were significantly associated with a successful VBAC or with chorioamnionitis. A p value of < 0.05 was considered significant.
Statistical analysis was performed by using IBM SPSS Statistics for Windows, Version 24.0 (Armonk, NY, USA). The local Institutional Review Board approved the study protocol.