Mark D. Hornstein, MD
IVF is in vitro fertilization. In vitro, in Latin, means in glass. What that means is that the fertilization of the egg by the human sperm happens in a Petri dish, in the laboratory, outside of the normal place where fertilization would occur, which is the human fallopian tube.
Common indications for IVF would include things like tubal factor, meaning that there are problems with the woman's fallopian tube, it might be damaged or it might be blocked; male factor, problems with the partner's sperm; endometriosis, a condition in which the lining of the uterus is grows outside of the uterus. A very common indication for in vitro fertilization would be what we call unexplained infertility, situations in which the physician has not been able to make a definitive diagnosis.
In order to do in vitro fertilization, the first step is to stimulate the ovaries. We call this ovulation induction. What happens is a woman takes multiple injections of hormones which are called gonadotropins. These are given by subcutaneous injections with very small needles that the woman can administer herself. This is done over a period of about 10 to 14 days.
During that time, we monitor the patient's progress. What that means is we'll do trans-vaginal ultrasounds and blood levels to allow the IVF physician to understand how the ovary is responding to the medications which the patient has been administering. At the appropriate point in the cycle, when the IVF physician determines that the eggs are mature, the patient will administer what we call a trigger shot. That's also an injection which allows the final maturation of the egg. The egg retrieval, the removal of the eggs from the ovary, occurs in a timed situation, 36 hours later.
The patient comes in, usually about an hour before the egg retrieval, and meets with our nurses, our doctors, and the anesthesiologist. The egg retrieval is done under light, general anesthesia, so the patient is actually unconscious, just like for other surgeries.
With trans-vaginal ultrasound, we place an ultrasound probe in the woman's vagina which is attached to a needle. Using ultrasound, we can guide the needle into the follicle, the fluid surrounding the egg, and we have a little suction device which allows us to capture the fluid surrounding the egg. Because the egg floats in the fallopian or follicular fluid, the egg is then captured as well. We move from follicle to follicle until all of the eggs are retrieved.
Once the eggs are in the Petri dishes, they're sorted, and counted by the embryologist, the scientist that takes care of the eggs and sperm. The partner's sperm are concentrated and then placed with the eggs in the Petri dish. That's called fertilization. The next morning, the embryologist can tell how many of the retrieved eggs were actually fertilized.
The last stage is embryo transfer.This is where the embryos, one or more embryos, are placed in the woman's uterus, in the womb. We do this under ultrasound. The embryo is placed in a little tiny plastic catheter, guided through the cervix, into the uterus, position is confirmed by ultrasound, and the embryo is released. This is done without anesthesia and the patient can walk off the table and head home.
So for most patients, under most circumstances, we're only transferring one or two embryos. The reason that we transfer fewer embryos now than we did previously, is because we're trying to avoid multiple gestations (twins or triplets). Embryos that are not transferred, which are grown appropriately out to day five, also called blastocysts, can be frozen for future use.