Human Chorionic Gonadotrophin (HCG) is a hormone that is used to trigger ovulation so that the egg can be extracted.
There is no immutable formula for when to perform the HCG injection. There are however some basic
rules that can give you a reasonably good idea of when to expect it. In general, HCG is administered after a minimum of six or seven days of gonadotropin stimulation. It’s given when the lead follicles are 17 or 18 mm and there are several trailing follicles of 14 or 15 mm and greater. The estradiol level should be at least 750, although there are occasionally cycles that are successful at levels between 500 and 750. The uterine lining should be at least 8 mm and be trilaminar.
Recognize that these are not hard and fast rules. We often decide that a cycle will do better if another day or so elapses prior to the HCG shot. But if you’re looking for general guidelines, these are good place to start.
Why do we give HCG?
Why not just go in and retrieve the eggs from the follicles when they’re big enough?
In nature, there is no surge of HCG prior to ovulation, but there is an LH surge, which you only remember from high school biology. The Luteinising Hormone (LH) surge performs several functions: it finishes off the maturation that the gonadotropins start, it initiates the process by which the follicle will burst and the egg be released, and it causes the egg to be released from the wall of the follicle. For these reasons, it is an extremely important part of the IVF stimulation. If the HCG injection is not performed, or if it’s performed incorrectly, we could have several bad outcomes to the cycle. A common one is that no eggs will be retrieved even with proper drainage of all the follicles visible on ultrasound. Without the HCG, the wall of the follicle will not let go of the egg and all the eggs will stay inside the ovary. Another possibility is that eggs, even if released from the wall of the egg are retrieved by a very aggressive aspiration of the follicles, will not result in any mature eggs. Again the HCG is needed to initiate final maturity. Immature eggs don’t fertilize, and they don’t develop. The bottom line is if you have difficulty with your HCG injection, don’t assume that the cycle will do just fine without it.
When should HCG be given relative to the retrieval?
We have defined some loose parameters that tell us when to give the HCG shot. We believe that ovulation occurs 36 to 38 hours after the initiation of the LH surge, or 36 to 38 hours after an HCG shot. At Saint Barnabas, we perform our egg retrievals 35 hours after the HCG shot. At this point the eggs are about to be released and we can catch them just prior to ovulation.
It’s important to realize that we do have a bit of a leeway here. A retrieval performed a half hour earlier or a half hour late should not have a harmful effect on the cycle of the wall. You can therefore relax when giving the HCG shot and not feel that you have push the plunger on the syringe just as the second hand crossed the 12 at the appointed time for the injection. It doesn’t hurt to give it right on time, but it’s not worth making yourself crazy over.
This is probably another good time to review the HCG injection technique. In the past, in the old days of Pergonal and Metrodin, all of the gonadotropin injections were done with the same 11/2 inch needles that we used for HCG. This took the stress off the HCG injection because it had been done many times before. Nowadays, with the subcutaneous gonadotropins that we all use, the HCG shot is often the first time a couple has done an intramuscular, as opposed to a subcutaneous injection. This should not be the source of a lot of stress, but it doesn’t hurt to review the technique several times.
What is Contained in the Injection?
Most HCG comes in two vials. One is sterile water, the other is the actual powder that contains the hormone. We use a 3 cc syringe to draw up one 1 cc of water. It’s important to realize that the amount of water is not very important. All you need do is make sure you dissolve all the powder in however much fluid you use. The water is simply a delivery system to get the powder out of the vial and into your body. It’s also important to realize that you probably don’t need all 10,000 units. We use 10,000 units as a standard dose, although most of the biologic activity would take place with even half, or maybe even less than half of the 10,000 units. So if a tiny amount leaks out or does not get from the vial into the syringe, there should be no damage to the cycle. After the 1 cc is drawn up out of the water vial, it’s injected into the powder vial and gently shaken. After changing needles, the fluid and powder mixture is then drawn back up into a syringe and ready for injection.
What is the Process?
The injection is a straightforward process. You pinch the area where the upper outer rivet would be; you insert the needle at a 90degree to the skin, pull back to see blood fills the syringe, and if it does not, simply inject the contents of the syringe.
If blood is returned into the syringe, this is not disastrous. Simply pull the needle completely out, hold the syringe needle up, and replace the needle. You can then re-administer the injection, small bit of blood in all, a 1/2inch away from the original injection site or on the other side, again approximately with the upper outer rivet of the back pocket of a pair of jeans would be.
If there are any problems with the HCG injection, just let us know. We can usually reassure everyone involved, the HCG was properly administered by simply drawing a Beta HCG (pregnancy hormone) level the day after the HCG shot, which is the day before egg retrieval. Whatever you do, don’t keep these problems to yourself. We can almost always come up with some strategy to get around any trouble you may have had with the HCG shot if you just let us know it occurred.
All that said, the most important thing is to be reassured that the HCG injection is a very minor hurdle that you should have no trouble completing easily.
We usually use your own serum as a primary component of the fluid we use to collect the eggs and incubate the early embryos. We collect this serum into two large syringes the day after the HCG injection. Why do we do this? Recall that in nature eggs are fertilized and the early embryos develop inside the fallopian tube. The fluid inside your fallopian is most similar to your own serum. After we draw this blood, we use a small sample to recheck your estradiol and progesterone levels. After the HCG shot, the progesterone level should rise and the estradiol should rise. In some cases the estradiol plateaus or falls. We have found that as long as the fall is less than 15% of the total the day before, the cycle should proceed without a problem. If there’s a huge drop in the estradiol, this usually indicates that one or more of the eggs may have ovulated on their own or may be degenerating. In some of these circumstances, retrieval is actually cancelled.