In a prospective randomised study involving primiparous women in spontaneous uncomplicated labour with cervical dilatation < 5 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%), in which 10 mL (50 g) of sufentanil will be added, as well as clonidine (150 µg) in one arm. The final concentration of clonidine in this arm will be 1.35 mg.mL-1. Parturients and midwifes assessing pain during labour will be blinded to the design.

We recently compared the analgesic effects of the two presentations of levobupivacaine available on the French market, (0.625 and 1.25 mg.mL-1 in pre-filled bags), both with sufentanil. It appeared that the high concentration was more powerful, however leading in some cases to give doses of levobupivacaine superior to the label's recommendations. This indicates to use the low concentration, with a risk of a poorer efficacy. Our aim is to show that efficacy can be restored with a systematic addition of clonidine, which has documented analgesic properties when administered perispinally.

Inclusion Criteria:

• Parturient is 18 years old
• ASA physical status 1 or 2
• Primiparity
• Singleton
• Gestational age is 36 weeks
• Spontaneous labour with cervical dilatation of 5 cm