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HPT After an hCG Trigger Shot

After getting an hCG trigger shot, women are advised to wait two or even three weeks before taking a home pregnancy test (HPT). Why is this? Since the test detects hCG -- the same hormone in the shot you just got -- testing too soon means a high risk of getting a false-positive result. However, there are other ways of testing earlier, each with pros and cons. Read on to learn more.

Testing and the Trigger Shot

So you've been to the doctor to talk about getting pregnant. You may even have been through dozens of appointments, ultrasounds, and injections. Now you've decided to try an approach that involves an hCG "trigger" shot to help with ovulation, but your doctor tells you that you have to wait two or three weeks before you can come back for a blood pregnancy test. You're also supposed to avoid taking a home pregnancy test (HPT).
At this point, two weeks (forget about three weeks; nobody is that patient) seems like an eternity. Can you take a home pregnancy test sooner? This article will talk about the hCG trigger shot and the reasons behind waiting to take a home pregnancy test.

The Science Behind the Trigger Shot

Luteinizing hormone (LH) is the hormone in the body that triggers ovulation. An increase in LH causes the body to release an egg from the mature follicle into the fallopian tube to be fertilized. This process is known as ovulation. Human chorionic gonadotropin (hCG) is a hormone secreted by an embryo, starting about six days after an egg has been fertilized. hCG prevents the body from eliminating the embryo and starting the menstrual cycle. It helps to stop the body from rejecting the implanting embryo. hCG also maintains the corpus luteum, which are the cells that produce progesterone, another hormone that is crucial in a successful pregnancy.
hCG and LH are very similar chemically. An hCG trigger shot is meant to mimic the natural LH surge and will help the follicle mature and trigger the release of the mature egg. Your doctor will monitor you closely with ultrasounds to identify when mature follicles are present and when the best time to receive the hCG injection will be.
Once given, ovulation will occur within 36 hours. If you are being induced for in vitro fertilization (IVF) or intrauterine insemination (IUI), timing is very critical, so make sure to follow your instructions carefully.
Last reviewed by: Arthur Schoenstadt, MD
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