OPU stands for oocyte pickup. Oocytes are acquired, by fine needle aspiration, from the follicles in the ovaries using ultrasonic guidance through the vaginal wall. Oocytes that are collected during this technique are then searched for/observed under a microscope, washed, and placed in cryovials for shipment. The cryovials are stored in an incubator for overnight shipment to a laboratory. Once at the laboratory, the oocytes are examined, fertilized and cultured. Resulting embryos are then sent back to the clinic a week later to be transferred into recipients. Embryos that are of higher quality may be frozen for direct transfer, if desired.