SufentanilFentanylAnalgesia, ObstetricalAnalgesics, OpioidAnalgesia, EpiduralBupivacaineAlfentanilAnesthetics, IntravenousInjections, SpinalAnestheticsAnesthesia, IntravenousAnesthesia, SpinalAnesthetics, CombinedAnesthetics, LocalPreanesthetic MedicationLabor, ObstetricDouble-Blind MethodPain, PostoperativeAdjuvants, AnesthesiaLabor Stage, FirstAnesthesia, ObstetricalAnalgesia, Patient-ControlledSubarachnoid SpaceAnalgesiaAmidesAnesthesia Recovery PeriodInfusions, IntravenousPruritusMidazolamPropofolAnesthesia, Epidural