|In vitro fertilization (IVF) was originally developed to treat women with absent or nonfunctioning fallopian tubes. As currently practiced, it is now successfully used to treat couples with other fertility problems including male factor, endometriosis, ovulatory dysfunction and unexplained infertility.
What is IVF?
Normally, one egg is released each month from the ovary and picked up by the fallopian tube. Sperm, after entering the vagina by sexual intercourse, travel through the cervix and uterus and into the tube, where they may encounter the egg and cause fertilization. The fertilized egg, called an embryo, then travels through the tube into the uterus. In IVF, fertilization occurs outside of the body in a laboratory dish (in vitro). Mature eggs are removed from the ovaries and placed with specially prepared sperm. Several days later, the resulting embryos are transferred back directly into the uterus. In many cases, implantation of one or more of these embryos into the uterine lining will occur, resulting in pregnancy.
IVF can be done using the single egg that normally matures during a woman's menstrual cycle. However, much better success rates are achieved by administering hormonal medications using a technique known as controlled ovarian hyperstimulation (COH). With COH, multiple eggs can be obtained, increasing the likelihood that multiple embryos will be available. The success of the IVF cycle depends, in part, on the number of embryos available for transfer.
The hormonal medications that are used for COH are called gonadotropins, and they are known by the brand names Menopur®, Bravalle®, Repronex®, Follistim®, and Gonal F®. They are given by injection for an average of ten days per cycle, and a partner is usually trained to administer these injections. The response to medication and the maturation of eggs is monitored using blood tests and ultrasound.
Egg retrieval is scheduled when the eggs are appropriately mature. The eggs are retrieved using ultrasonographic guidance by placing a needle through the vaginal wall and into the ovaries. All retrievals are performed by one of our physicians in our operating room and are done under anesthesia. Rarely, the ovaries are inaccessible through the vagina, in which case the retrieval can be performed via laparoscopy.
Upon retrieval, the eggs are immediately given to the embryologist in the adjacent laboratory. After each egg is identified, it is placed into a culture dish containing special nutrient medium and maintained under carefully controlled conditions. Meanwhile, the husband produces a semen sample that is processed to separate out the most highly motile sperm. Later that day, the eggs are incubated together with the specially prepared sperm.
The embryos grow and divide in the IVF laboratory for three days, at which time they are transferred back into the woman's body. In most cases, a physician transfers embryos directly into the uterus using a soft, thin plastic catheter that is passed through the cervix. The embryo transfer is a nonsurgical procedure that generally is no more uncomfortable than a Pap smear or insemination.
Gamete intrafallopian transfer (GIFT) is a procedure similar to IVF but different in that fertilization occurs in the fallopian tubes. Laparoscopy is used to retrieve the eggs, which are then mixed with sperm and immediately transferred into the fallopian tube, where fertilization may occur. Candidates for GIFT must have at least one normal fallopian tube and no significant male factor. If more eggs are obtained than can safely be transferred, IVF can also be performed during the same cycle with cryopreservation of the resulting embryos. Given that GIFT involves laparoscopy and is therefore much more invasive than IVF, and given that the success rates with IVF at least equal those of GIFT, GIFT is rarely done.
ZIFT and TET
Zygote intrafallopian transfer (ZIFT) and tubal embryo transfer (TET) are variations of IVF in which the embryo transfer is done via laparoscopy into the fallopian tubes three days following egg retrieval. These procedures are reserved for the rare occasions when the cervix is too stenotic and will not allow for embryo transfer.
If more embryos are obtained than can safely be transferred to the uterus, they can be cryopreserved (frozen) for later use. Cryopreservation of embryos can increase the chance of achieving a pregnancy from a single egg retrieval, while avoiding the risks that may accompany the transfer of too many embryos at one time. Embryos that are cryopreserved are carefully thawed at a later date and transferred into the uterus at the appropriate time in a woman's menstrual cycle. While some embryos may not survive thawing, there is no increased risk of congenital abnormalities when pregnancy does occur.