Published: Sept. 26, 2008
Updated: Sept. 8, 2010
Human chorionic gonadotropin (HCG) has a chemical structure that is very similar to luteinizing hormone (LH), which triggers ovulation. HCG is also the hormone produced by pregnancies from the chorionic villi and placenta.
A pregnancy test is essentially a test for the presence of HCG. Since HCG has a structure like LH but lasts much longer in circulation than LH, HCG can be used to trigger ovulation at the appropriate time.
When the monitoring team feels your follicles are at the appropriate size to trigger ovulation you will be instructed on a time to take HCG. This is often referred to as "released".
The type of cycle and day of the procedure (oocyte retrieval or insemination) will determine what time the HCG injection will be given.
Several scenarios are included below:
Timed intercourse can be done with Clomid and controlled ovarian hyperstimulation (COH) cycles. Patients taking Clomid may be given 10,000 units HCG whereas patients doing COH generally get 5,000 units of HCG.
These injections are administered in the clinic at the time of the monitoring visit since intercourse will need to be planned approximately 37 hours from the time of injection.
As an example, if HCG is given at 9:00 a.m. then intercourse should be planned for around 10:00 p.m. the following night. This type of timing usually works for most couples that work during the day.
The exact timing is a recommendation and should not be considered an absolute. Fortunately, nature does not require such perfect timing.
Inseminations with washed and donor sperm will be scheduled 39 to 42 hours after HCG injection. Five thousand units of HCG is usually administered at 6:00 p.m. two days prior to the scheduled insemination.
For example, a patient with appropriately sized follicles seen on Monday is directed to stop all injections and take 5,000 units of HCG at 6:00 p.m. She will then be seen on Wednesday for an insemination around 9:30 a.m. to 10:00 a.m. (Semen samples will be collected at 8:00 a.m. if applicable.)
IVF patients now take 5,000 units of HCG at 37 hours prior to retrieval. There is a margin of several hours before the release of the oocytes into the abdomen, again reinforcing the above statement that timing is not absolute.
Different IVF centers use different times for their retrievals and have become comfortable using their own timing.
Be sure to take your medication at the time that was specified for you. Written directions are provided at the monitoring visit prior to your retrieval.
Learn more about fertility medications below.