• Javier Pascual-Ramírez, Javier Haya, Faustino Pérez-López, and Silvia Gil Trujillo.
• Anesthesiology Department, Hospital General de Ciudad Real, SESCAM, C/Besana, 2b, 13170 Miguelturra, Spain. pascrib@hotmail.com
• Arch. Gynecol. Obstet. 2012 Oct 1; 286 (4): 873-80.

ObjectiveTo create a Proportional Hazards Model of prospective factors associated with time-to-vaginal-delivery (TTVD).MethodsWe analyzed a group of 144 women undergoing childbirth who received one out of two possible axial analgesia techniques, to find-out factors associated with TTVD. The patients were randomly assigned to receive either a levobupivacaine labor epidural (bolus concentration 0.25 % or less; infusion concentration 0.125 % or less) or a combined spinal-epidural procedure (morphine 0.20 mg, fentanyl 25 µg and hyperbaric bupivacaine 2.5 mg as spinal components) for labor analgesia. The factors initially chosen were: mother age, height and weight, parity, gestational age, newborn weight, type of labor, analgesic procedure, levobupivacaine and fentanyl doses, Bromage scale, pain Numeric Rating Scale, and a satisfaction interview. Cesarean section was the censored variable in our model. A systematic multivariate Cox regression was performed.ResultsOur Final Model stated that nulliparous women had 2.5 times more chances of having longer TTVD than primiparous (p < 0.001, CI 1.76-3.8), and 3.4 times more (p = 0.015, CI 1.27-9.25) than multiparous. Women with oxytocin-augmented labor had 2.05 times more chances (p = 0.001, CI 1.31-3.22) of having longer TTVD than patients without oxytocin. An induced partum had 3.8 times more chances (p < 0.001, CI 2.09-6.8) of having longer TTVD compared to a spontaneous partum.ConclusionParity, labor augmentation, induction of labor and fetal weight determine TTVD; axial analgesia-related factors do not contribute to the model.

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