The purpose of this study is to assess pain, at or after oocyte retrieval, the effectiveness of self-controlled inhalation analgesia by nitrous oxide (N2O of 50% and 50% O2) by the patient compared to a local anesthesia combined with a tablet of 0.5 mg of Alprazolam.

Oocyte retrieval is a major event during in VITRO-fertilization, with or without sperm micro-injection. Initially done by laparoscopy with general anesthesia, the oocyte collection is now carried out by trans-vaginal controlled ultrasound puncture. This potential painful event, related to trans-vaginal puncture or mechanical movements of the stimulated ovary, requires analgesia or anesthesia. General anesthesia is certainly effective in terms of collected oocytes. It remains, however, a heavy time consumer, with personal risks and distributor of anesthetic agents in blood or follicular fluid. These products could have a deleterious effect on early embryonic development or implantation. Few data are available concerning these risks in the literature. General anesthesia is still essential for pusillanimous patients or for patients with a heavy surgical past. Nitrous oxide is an inhaled gas with properties widely used in obstetric during parturition. It is regularly used during general anesthesia performed for oocyte retrieval. With a gas composed of 50% N2O and 50% O2, its main interest is to provide analgesia in a state of conscious sedation. The effects of nitrous oxide in this form had never been assessed on the clinical or biological Oocyte collection. We conducted a preliminary study to assess pain in patients receiving local anesthesia, according the current protocol. Thus, 44% of patients had severe pain (VAS> 40/100) during or just after transvaginal oocyte retrieval. In our preliminary experience, immediate or distance post-operative pain was high and we plan to evaluate the benefit of analgesia with nitrous oxide in terms of immediate post-operative pain with a prospective, randomized and controlled study as compared with local anesthesia associated to Alprazolam.

Inclusion Criteria:

• patient requiring a first or second oocyte retrieval procedure for IVR or ICSI after ovarian stimulation by gonadotrophin
• agreement to participate to this study

Exclusion Criteria:

• absolute indication for oocyte retrieval with general anesthesia
• no agreement to participate to this study,
• painfully known patient-not easy ovarian vaginal accessibility for monitoring or puncture
• respiratory pathology-chronic liver, kidney pathology, immunodeficiency, -contraindication to the medications used during the protocol