Combined spinal-epidural Duration of labour Foetal outcome Labour analgesia Adult Analgesia, Epidural Analgesia, Obstetrical Anesthesia, Spinal Apgar score Delivery, Obstetric Drug Therapy, Combination Female Humans Labor, Obstetric OPIOID ANALGESIA PROGRESS Pregnancy Prospective Studies Time Factors Treatment Outcome Young Adult adult cesarean section combination drug therapy controlled study emergency epidural analgesia epidural anesthesia female human