The hCG trigger shot contains a synthetic form of the hormone human chorionic gonadotropin. There are several brand names for the hCG trigger shot including Ovidrel, Profasi, Pregnyl, and Novarel.
What is hCG?
hCG is known as the “pregnancy hormone.” hCG is produced in early pregnancy by the cells that will eventually form the placenta. hCG maintains the corpus luteum which is responsible for progesterone production during the second half of the menstrual cycle and during early pregnancy.
Why Is the hCG Trigger Shot Used as a Fertility Treatment?
The hormone hCG helps in the follicle maturation process and triggers the release of mature eggs from the follicles. Generally, you will be given a medication to induce ovulation prior to taking the trigger shot. Medications like Clomid or HMG will help your ovaries to develop follicles for ovulation. The hCG trigger shot will then assist in the final maturation process and ensure that the mature eggs are released from your follicles.
If you are taking the hCG trigger shot, you will be monitored closely by your doctor. You will need to go in for ultrasounds to monitor the progress of your developing follicles. By measuring the size of your follicles, your doctor can determine whether your eggs are “ready” to be released. When the follicles are mature, you will be provided with instructions on how and when to take the trigger shot. It is given by either an intramuscular or subcutaneous injection that you will do yourself. Follow your doctor’s specific instructions on using this medication.
Will the HCG Trigger Shot Affect an Ovulation Test?
The hCG mimics the hormone LH. LH is what an ovulation test detects for. Because of this, you should see a positive ovulation test shortly after taking the trigger shot. Some doctors will recommend testing for your LH surge at home prior to taking the trigger shot. If you have an LH surge on your own, you may not need to use the trigger shot. However, depending on why you are receiving the trigger shot, you may be advised to use the trigger shot even if you have a surge on your own. You should consult your doctor for specific instructions on this.
How Long After Taking the HCG Trigger Shot Will You Ovulate?
On average, a woman will ovulate around 36 hours after receiving the hCG injection. If your ovulation is being induced for IUI or IVF, the timing of your injection is critical. You should be given specific instructions on when to take the trigger shot so that your procedure can be scheduled for the most precise time.
Will the HCG Trigger Shot Affect a Pregnancy Test?
Since hCG is the hormone that pregnancy tests are detecting, it will affect the results of a pregnancy test. If you test shortly after taking the hCG shot, you will receive a positive test and the results will not be accurate. HCG from the trigger shot can remain in your body for up to 14 days after you have received the injection. Your doctor may advise you to wait two weeks before taking a home pregnancy test, or he may have you come in for blood work to confirm pregnancy instead. A quantitative beta hCG test can be given to see if your hCG levels are rising. This would be indicative of pregnancy as hCG from the trigger shot should be declining and not rising.
Some women “test out” the hCG by taking a pregnancy test shortly after receiving the hCG injection and testing daily until they no longer get a positive result. While this may be reassuring, this does not guarantee accurate results from a pregnancy test.