What is the optimal follicular size before triggering ovulation in intrauterine insemination cycles with clomiphene citrate or letrozole? An analysis of 988 cycles.
In the normal menstrual cycle, a follicle grows each month. When the follicle reaches about 20mm in diameter, it spontaneously releases an egg. This is called ovulation.
Some women who require help conceiving need to take fertility drugs such as clomiphene citrate (Clomid) or letrozole (Femara) in order to ovulate. These drugs are taken in the early part of the menstrual cycle and help stimulate the growth of a follicle and subsequent ovulation.
Ultrasound scans can be performed to see if the follicle grows properly. If the release of the egg doesn’t occur naturally, a hormone (human chorionic gonadotropin – hCG) is administered to initiate the process.
This study evaluated how triggering ovulation with hCG at different follicle sizes affected pregnancy rate. It was determined that the chance of pregnancy is slightly improved if ovulation is triggered when the largest follicle reaches over 22mm in diameter.
What This Means For You
If you are undergoing fertility treatment with either Clomid or letrozole medications, it is likely that you will have a better chance of achieving pregnancy if your largest follicle is over 22mm in diameter.
Unfortunately, this is not always possible. For example, your body may trigger ovulation naturally before you are able to reach this follicle size. Alternatively, your doctor may need to trigger ovulation earlier to reduce your risk of multiple pregnancy.
Fertility and Sterility. 2012 May;97(5):1089-94.e1-3
Palatnik A, Strawn E, Szabo A, Robb P. (USA)
Click here for full study on National Institutes of Health.