“Will you make me some magic with your own two hands?Can you build an emerald city with these grains of sand?Can you give me something I can take home?These are pointed questions fueled by strong desires; originally penned by Meat Loaf but paraphrased by just about every patient who comes in here to establish a healthy, ongoing pregnancy. If the good old fashioned way is “natural” then what we do in IVF must be the converse of that and, if indeed what we do is “unnatural” – it must be magic. Not so. We cannot make a bad egg or a bad sperm good. We cannot change genetics.
In the IVF lab fertilization of the eggs is the first but the easiest hurdle to overcome.If the sperm parameters meet acceptable standards then we allow the eggs to choose their mates. ICSI (intracytoplasmic sperm injection) is a laboratory intervention employed if there are few progressively motile normally shaped sperm to work with. With this technique individual sperm are selected, picked up with microinstruments, and injected into eggs that have been retrieved and prepared to receive them. Fertilization, either “natural” or assisted, occurs on “Day 0”. On “Day 1”, the following day, we see how many eggs have fertilized.The fertilized eggs (now called preembryos) are thencultured and grown for 5-6 days during which time they navigate a genetic obstacle course. Those embryos that are genetically competant will make it to the blastocyst stage and, if they have sufficient stem cell masses, will be appropriate for transfer to the uterus. As most sperm-egg combinations are not normal,having more eggs to fertilize (up to a point : 12-15 is a good yield) will increase the liklihood of ending up with a few embryos that can “go the distance”.With IVF it really is a numbers game and, in this game, the eggs and the sperm run the show.
So if we would do anything to achieve a healthy pregnancy but we can’t change the genetics of the “raw materials” what, exactly, can we do to improve upon nature? We can do an awful lot for male factor infertility: we can find and isolate the good sperm and make sure it gets where it needs to go. (For the most part normally shaped sperm contain normal DNA.) We can culture embryos to the blastocyst stage as our laboratoryculture conditions simulate the hormonal and enzymatic environments of the fallopian tubes where embryo development usually occurs. In so doing we can effect embryo development for women with diseased or absent tubes and we can bipass the normal fallopian tube conduit whose function is to get blastocyst -stage embryos where they need to go. In addition, by creating more sperm-egg combinations in any one cycle we are taking a very inefficient process, human reproduction, and making it more efficient.
Special thanks to Meat Loaf for his invaluable assistance in the preparation of this post.