In a prospective randomised study involving primiparous women in spontaneous uncomplicated labour with cervical dilatation > 7 cm, epidural analgesia will be given with an initial volume of 20 mL anaesthetic solution, followed by a standardised algorithm of top-up manual injections to achieve analgesia, then by a patient-controlled regimen with 5-mL self-administered boli in addition to a continuous infusion of 5 mL.hr-1. The anaesthetic solution will be levobupivacaine presented in 100-mL bags from the market, 0.0625%, or 0.125%, in which 10 mL (50 µg) of sufentanil will be added. The final concentrations will be 0.568 and 1.136 mg.mL-1 respectively, both with sufentanil 0.45 µg.mL-1. Parturients and midwifes assessing pain during labour will be blinded to the design