Ovulation typically occurs 24–40 hours after a trigger injection (hCG or other ovulation trigger), with the most common window being 36 hours. During assisted reproductive procedures like IVF, doctors administer a trigger shot to stimulate final egg maturation and release. The exact timing depends on the specific medication used: intramuscular hCG injections usually trigger ovulation around 36–40 hours later, while subcutaneous hCG or GnRH agonist injections may result in earlier ovulation, sometimes within 24–36 hours. Egg retrieval during IVF is typically scheduled 34–36 hours after the trigger to capture mature eggs before they're released naturally. This precise timing is critical for successful retrieval; if the procedure occurs too early, eggs may be immature, while waiting too long risks spontaneous ovulation and egg loss. Patients are given specific instructions about when to administer the trigger injection and when to arrive for their retrieval procedure. The trigger injection itself contains hormones that complete the final stages of meiosis and weaken the follicle wall, allowing the egg to be released. Individual variation occurs due to differences in hormone sensitivity, age, ovarian reserve, and stimulation protocol, which is why fertility specialists monitor each patient's cycle closely and individualize timing recommendations.