At the end of your stim phase, you’re given a different medication called a “trigger shot”. This is administered exactly 36 hours before your egg retrieval is scheduled and lets your ovaries know that it’s time to mature the eggs and prepare them for release. Before they are actually released, the procedure is performed to aspirate each of the eggs out of their follicles. The follicles have grown to be about 20mm at the largest, and usually at least 14mm if they are containing a mature egg, and they’ll continue to grow after the trigger shot, but the eggs themselves are still microscopic.