Oocyte retrieval, that is the collection of oocytes (eggs) contained in follicles grown in the ovaries after drug stimulation, is performed 32-36 hours after injecting chorionic gonadotropin. The woman comes to the IVF Unit without having taken any food or drink for the previous 8 hours at least (as she will be administered a mild sedation against pain). Oocyte retrieval requires a thin pipe fitted on the transvaginal ultrasound probe through which a needle that is connected to a suction system is inserted. Under direct transvaginal ultrasound guidance the needle advances towards the ovaries through the vaginal walls to puncture the follicles and draw up the follicular fluid. The embryologist examines the fluid under the microscope to retrieve the oocytes contained. After having punctured all the follicles, the egg collection ends; the woman awakens and is ready to leave the Unit 1 or 2 hours later having received all necessary advice. In the meanwhile and after having confirmed the success of egg collection, the husband is asked to give semen sample to be used for the in vitro fertilization. From the day of oocyte retrieval and on, the woman must commence the appropriate supportive treatment (basically comprising administration of progesterone in form of vaginal gel or suppository, low-dose aspirin and cortisone, antibiotics and sometimes estrogen tablets) aiming at preparing the endometrium to accept the fertilized egg for the achievement of a pregnancy.