when does a mature oocyte complete meiosis i?

A mature oocyte completes meiosis I the day before ovulation, in response to a surge in luteinizing hormone (LH). Meiosis I resumes from a prolonged arrest at the diplotene stage of prophase I and finishes with the extrusion of the first polar body, indicating the completion of the first meiotic division. After this, the oocyte enters meiosis II and arrests again at metaphase II until fertilization.