ICSI Vs IMSI
Doctors love coining new terms , and this seems to be especially true for IVF specialists. Infertile couples have to learn a whole alphabetic potpourri of medical terms - ranging from IVF to GIFT to ICSI to ZIFT. It's easy to get lost and confused; and most patients can't seem to make sense of any of these !
To add insult to injury, many IVF doctors claim to use "the new and latest" technique to improve pregnancy rates. Obviously, every "new" technique needs a new name - so the confusion gets compounded. It's a competitive business, and IVF doctors always try to keep one step ahead of other doctors ! While this is good because it allows patients access to the newest technology, the downside is that many doctors will then promote a particular technique - not because it is better, but simply because it is new !
It's easy to get a lot of press coverage for a lot of these "new" advances, because reporters are often not medically sophisticated, and most are quite happy to oblige their doctor friends. Poor patients get even more confused - and will often flock to the doctor featured in the latest article, in the hope that this new technique will give them a baby ! This then sets up a vicious cycle, where doctors compete with each other, in order to be featured in the press. It often becomes a game of one-upmanship, where the doctor with the best PR firm wins !
The newest kid on the block is a term called IMSI ! This stands for Intracytoplasmic Morphology Selected sperm Injection - quite a mouthful ! This is simple a modification of the standard ICSI technique, in which the sperm are magnified even further. The rationale is very logically appealing - let's use higher powered magnification, so we can select the "best " sperm for ICSI ! One would therefore expect that this technique would result in higher pregnancy rates after ICSI.
Unfortunately, this is not true in real life. Not only does IMSI not improve pregnancy rates as compared to ICSI, it can actually decrease them. This is because IMSI takes longer to perform than ICSI. The embryologist has to keep the fragile eggs ( into which the sperm has to be injected ) on the micromanipulator for longer while doing IMSI, and since eggs are very sensitive, this extra exposure can cause them to get damaged.
Now, since the sperm provide 50% of the genes of the embryo, it is logical to assume that 50% of the time the reason for genetically abnormal embryos ( and thus failed IVF cycles and recurrent miscarriages) would be genetically abnormal sperm !
However, what is logical is not always true ! In reality, studies have shown that there is no correlation between abnormal sperm and failed IVF or miscarriages.
Let's look at a very common reason for infertility. This is the problem of abnormal sperm morphology, known medically as teratozoospermia. These are men who have a very large proportion of abnormally shaped sperm - more than 95% abnormal forms. The standard treatment for these men is ICSI, in which a single sperm is injected into an egg to fertilise it.
Now one would logically expect that the fertilisation rate in these men would be very low; or that many of these embryos would be abnormal, as a result of which they would not implant. Surprisingly, this is not true - and the fertilisation and pregnancy rate in these men is exactly the same as it is in men with normal sperm. This means that abnormal sperm do not create abnormal babies ! This is one of the reasons why all the new sperm tests which check for sperm DNA integrity are of such little clinical value.
This is very counter-intuitive, but this is the truth. What are the possible explanations ? Why do men play such a seemingly unimportant role in human reproductive wastage ?
One hypothesis is that it is possible that the egg can correct for the sperm's problems. After all, the egg is much larger than the sperm; and the cytoplasmic machinery and energy which drives cell division after fertilization comes only from the egg. The other possibility is that the defects caused by abnormal sperm are lethal and incompatible with embryo development beyond a particular point.
In the mouse lab, it would be interesting to deliberately inject chromosomally abnormal sperm into eggs, and then to follow their fate, to try to figure out a possible explanation !