Author: Ciera Roberts, MSN, APN, WHNP-BC
One of the questions that patients often ask us in the office here at Southeastern Fertility is whether or not to use an HCG trigger shot for the timing of an intrauterine insemination (IUI). So is it better to use a trigger shot than to use an at-home ovulation predictor kit? The answer is (drum roll please): There isn’t one correct answer.
We aim to do an IUI at the optimal time in a treatment cycle. The optimal timing of an IUI is at the time ovulation occurs; therefore, it is important to be able to accurately predict that time frame. Ovulation is triggered by a surge in luteinizing hormone (LH), which is released by the pituitary gland, when the ovarian follicle or follicles become mature. The egg is released from the follicle about 36 hours after the LH surge.
When we plan to use an HCG trigger shot, the patient is monitored via transvaginal ultrasound and hormone blood tests at intervals until the ovarian follicle or follicles are determined to be mature. Once we estimate that the follicle is ready (usually when it measures 18-22 mm in average diameter), an injection of HCG is administered. HCG is very similar to LH and thus the trigger shot serves as the LH surge, and IUI is scheduled accordingly anticipating that the egg(s) will be released about 36-42 hours following the HCG injection.
How does this compare to using an at-home ovulation predictor kit (OPK)? Well, in most patients the LH surge will be detectable in the urine after the surge is noted in a blood test. Usually the egg is released the day following a positive OPK. So, an IUI is ideally performed the morning after a positive OPK. Patients will typically begin testing on cycle day 12 and test every day until the test is positive.
Current research indicates no significant difference in either clinical pregnancy rates or live birth rates when comparing home monitoring of ovulation with OPKs to ultrasound monitoring and HCG triggering. Therefore, the choice is patient specific.
If your schedule doesn’t allow the time commitment for multiple ultrasound visits and lab draws, and you are confident in your ability to do in-home monitoring, then OPKs may be the best option for you. However, if you have had difficulty interpreting OPK results in past cycles, or you’re simply afraid that you might miss the positive result, then ultrasound monitoring and HCG trigger shot may reduce your anxiety and uncertainty. Using a trigger shot also takes some of the guesswork out of the timing of an IUI, and may be beneficial if there are potential scheduling conflicts near ovulation (such as you or your spouse leaving town on a business trip).
The bottom line is that there is no right or wrong answer, and you should talk to your doctor about what is going to be most beneficial for you.