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

Since epidural analgesia has been developed to relieve labour pain, many solutions have emerged to lower risk / efficacy ratio, by using low-concentrated and/or less toxic local anaesthetics. Levobupicaine emerges as a safer alternative than its racemic parent . It is available on the French market in pre-filled bags with two different concentrations (0.625 and 1.25 mg.mL-1), both indicated for analgesia in postoperative context and in labour, without more precision. Presentation in bags allows preparing once at the initiation of epidural analgesia a solution usable throughout labour, leading the anaesthetist to a univocal choice, mostly following his/her personal beliefs. Our aim is to compare the effects of epidural analgesia under these two presentations. Sufentanil will be added to levobupicaine whatever the concentration used. This trial is conducted in primiparous, in which pain during labour is commonly more resistant to relief.

Inclusion Criteria:

• Parturient > 18 years old
• ASA physical status 1 or 2
• Primiparity
• Singleton
• Gestational age > 36 weeks
• Spontaneous labour with cervical dilatation > 7 cm

Exclusion Criteria:

• Gestational age < 36 weeks