Intrauterine insemination (IUI) is a common fertility treatment that involves placing sperm directly into the uterus around the time of ovulation to increase the likelihood of fertilization. A key element within an IUI cycle is the administration of a “trigger shot,” which precisely orchestrates the timing of key reproductive events to optimize the chances of a successful pregnancy.
What is a Trigger Shot?
A trigger shot is a medication administered to induce ovulation, precisely controlling the timing of a mature egg’s release from the ovary. The most common type contains human chorionic gonadotropin (hCG), a hormone that mimics the body’s natural luteinizing hormone (LH) surge. LH is naturally produced by the pituitary gland and signals the ovaries to prepare for ovulation. Some trigger shot options may also use a GnRH (gonadotropin-releasing hormone) agonist or a combination.
How the Trigger Shot Works
The trigger shot initiates a series of biological processes leading to egg release. When hCG is administered, it acts similarly to the natural LH surge. This hormonal signal prompts the final maturation of eggs within the ovarian follicles. Following maturation, the trigger shot causes the mature egg to detach from the follicle wall and release from the ovary into the fallopian tube. This entire process typically occurs within a specific window after the injection, allowing for precise coordination with fertility procedures.
Administering the Trigger Shot
The trigger shot is precisely timed within an IUI cycle to align with anticipated ovulation. It is typically administered 34 to 36 hours before the scheduled intrauterine insemination procedure. This timing ensures that the eggs are mature and ready for release when the sperm are introduced. Fertility clinics often instruct patients to take the shot in the evening, maximizing the chances of synchronization with the body’s natural rhythms.
The injection is commonly given subcutaneously, meaning just under the skin, often in the lower abdomen or thigh. Subcutaneous injections are generally self-administered at home.
Preparing for and Experiencing the Trigger Shot
Before receiving the trigger shot, patients undergo careful monitoring through ultrasounds and blood tests. These assessments confirm that the ovarian follicles have reached an optimal size, indicating the eggs are mature. This monitoring helps fertility specialists determine the precise moment for the shot, ensuring the best chance of success.
After the injection, individuals may experience some mild and temporary side effects. Common reactions include pain, redness, or swelling at the injection site. Hormonal changes can lead to symptoms such as temporary bloating, mild abdominal or pelvic discomfort, and breast tenderness. These sensations are generally manageable and typically subside within a few days as the body responds to the medication.
The Trigger Shot’s Role in IUI Success
The trigger shot enhances the success rates of intrauterine insemination. Its precise action of inducing ovulation ensures that the egg is released at a predictable time. This controlled timing allows the IUI procedure to be scheduled when the egg is most viable for fertilization. Sperm introduced during IUI can then meet the newly released egg in the fallopian tube, optimizing the opportunity for conception.
Studies have indicated that using a trigger shot in IUI cycles can increase pregnancy rates. For example, some research found that the pregnancy rate with a trigger shot was 18.2%, compared to 5.8% without it. By taking the guesswork out of ovulation timing, the trigger shot maximizes the chances that sperm and egg are present at the same time, which is fundamental for successful fertilization in an IUI cycle.