A trigger shot is a carefully administered hormonal injection used in fertility treatments to induce the final maturation of eggs and prompt their release. This injection plays a significant role in procedures such as in vitro fertilization (IVF) and intrauterine insemination (IUI). Its primary purpose is to precisely control the timing of ovulation, ensuring that eggs are optimally prepared for collection or fertilization. The shot helps synchronize the reproductive cycle, allowing fertility specialists to plan subsequent steps with accuracy.
The Science Behind the Shot
The trigger shot typically contains human chorionic gonadotropin (hCG), a hormone that closely resembles the body’s naturally occurring luteinizing hormone (LH). In a natural menstrual cycle, a surge of LH signals the ovaries to release a mature egg. When administered as a trigger shot, hCG mimics this natural LH surge, prompting the ovarian follicles to complete the final stages of egg maturation.
This hormonal signal causes eggs within dominant follicles to undergo meiosis, preparing their chromosomes for potential fertilization. Following maturation, hCG initiates the release of eggs from their follicles. Mature follicles, fluid-filled sacs containing the eggs, respond to hCG by preparing for rupture. This ensures eggs are fully developed and ready for natural conception, collection during IVF egg retrieval, or fertilization during an IUI procedure.
Administering the Shot and Crucial Timing
The trigger shot is administered as a subcutaneous injection, just under the skin. Many individuals or their partners are taught to self-administer the shot at home. This method allows for convenient and precise timing, which is important for the success of fertility treatments.
The precise timing of the trigger shot is important because ovulation typically occurs approximately 34 to 36 hours after the injection. This window allows fertility specialists to schedule egg retrieval for IVF before natural release, or to time intrauterine insemination (IUI) for optimal conception. The exact hour for administration is determined by the fertility clinic based on monitoring follicle size through ultrasound and assessing hormone levels. This synchronization ensures eggs are in their mature state, maximizing potential for successful fertilization and pregnancy.
What to Expect After the Trigger Shot
After receiving the trigger shot, individuals may experience changes as their body prepares for ovulation or egg retrieval. Common sensations include mild cramping, bloating, and abdominal tenderness. These are normal signs that the ovaries are responding to the medication and eggs are maturing.
Fertility clinics schedule follow-up appointments, which may involve ultrasounds or blood tests, to confirm the shot’s effect and ensure progression as expected. Following the trigger shot, the next steps in the fertility process are planned. For IVF, egg retrieval is scheduled about 36 hours post-injection; for IUI, the procedure occurs within 24 to 36 hours. Mild side effects include injection site reactions (redness, soreness), fatigue, or headache. These are temporary, but it is advisable to contact a doctor for any concerns, especially if symptoms are severe or suggest ovarian hyperstimulation syndrome (OHSS), such as severe abdominal pain or swelling.