Effect of Dural Puncture Epidural Analgesia on Oxytocin in Early vs Late Labor

Oxytocin is a key hormone that regulates uterine contractions during labor. Dural Puncture Epidural Analgesia (DPEA) is a modern technique for labor pain relief that provides faster onset and more reliable analgesia than standard epidural.While it is known that neuraxial analgesia can suppress oxytocin levels, it is unclear whether this effect depends on the stage of labor at which analgesia is administered. This prospective comparative study will enroll 120 pregnant women in spontaneous labor who request DPEA, divided into two groups: Early group (cervical dilation≤5 cm, n=60) and Late group (cervical dilation≥6 cm , n=60). Both groups receive identical DPEA (a total volume of 15 mL containing 0.1% bupivacaine and 100 µg fentanyl is administered through the epidural catheter, following dural puncture with a 26G spinal needle without intrathecal drug injection). The primary outcome is the percentage change in plasma oxytocin from baseline (T-0, before analgesia) to T-Eff (30 minutes after onset of effective analgesia defined as VAS\<2). Patients who received any exogenous oxytocin (induction or augmentation) before T-0 are excluded to ensure that the measured oxytocin represents endogenous production. The study will contribute to understanding how the timing of neuraxial analgesia relative to labor progression affects the endogenous oxytocin system, with potential implications for optimal clinical timing of labor analgesia administration.