COMPARISON OF LABOR ANALGESIC EFFECTIVENESS OF PROGRAMMED INTERMITTENT EPIDURAL BOLUS USING ROPIVACAINE AT DIFFERENT VOLUMES COMBINED WITH FENTANYL. YHCĐ [Internet]. 2026 Jan. 15 [cited 2026 Sept. 8];67(1). Available from: https://tapchiyhcd.vn/index.php/yhcd/article/view/4114