Trigger Shot

The trigger shot simulates the natural LH surge that causes ovulation, but is timed precisely so eggs are retrieved or insemination occurs at the optimal moment. In IVF, retrieval is scheduled exactly 35–36 hours after the trigger. In IUI, insemination is timed 24–36 hours after the trigger.

The two main trigger types are hCG (Ovidrel, Novarel, Pregnyl) and GnRH agonist (Lupron trigger). hCG triggers are more reliable but carry higher OHSS risk. Agonist triggers can only be used in antagonist protocols and virtually eliminate OHSS risk, making them preferred in high-responders when a freeze-all strategy is planned. Dual triggers (both hCG and Lupron) are sometimes used in poor responders.