A “trigger shot” is often used with timed intercourse, intrauterine insemination (IUI), or in vitro fertilization (IVF) procedures. If the shot is part of your protocol, your doctor will tell you when and how to do it in relation to other medications and procedures.
Trigger shots are given once per cycle before ovulation. They can be injected either into the muscle (intramuscularly) or under the skin (subcutaneously). They’re most typically self-administered, and many women choose to do the shot under the skin on the abdomen.
What does the trigger shot do?
Whereas other gonadotropins — like follicle-stimulating hormone (FSH) and LH — work on both growing and maturing the eggs, a trigger shot of hCG helps the ovaries release those mature eggs as part of ovulation.
With timed intercourse or IUI, this means that your doctor can pinpoint when ovulation is likely to occur and then time sex or your IUI for the best results. Here are the steps:
- Your doctor will monitor your follicles until they’re ready.
- You’ll administer the shot as directed.
- Your doctor will schedule your procedure (or tell you to have sex) to coincide with ovulation a certain number of hours after the shot.
With IVF, the trigger shot is used before egg retrieval to help facilitate a process called meiosis. In meiosis, eggs go through an important division where its chromosomes go from 46 to 23, priming them for fertilization. Before the eggs release naturally, your doctor will schedule your egg retrieval procedure to collect them for fertilization in a lab. Once fertilized, the embryos will then be transferred back into the uterus for implantation.
The timing is similar with IVF. Your doctor will monitor your ovaries via ultrasound and give you the green light to do the trigger shot when your follicles are of a size that your clinic specifies. This might be anywhere between 15 and 22 millimeters. This is usually between day 8 to 12 of your cycle. After you do the shot, you’ll schedule your egg retrieval for within 36 hours. Then the eggs are fertilized using your partner’s or a donor’s sperm. The fertilized eggs are then either transferred (when doing a fresh transfer) between 3 and 5 days after your retrieval or frozen (for later transfer).