Assisted Reproductive Technologies |
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The term "Assisted Reproductive Technologies" (ART) correctly can be applied to any therapy that manipulates sperm and eggs in order to promote conception, but in common usage, it appears as a substitute for In Vitro Fertilization (IVF).
In Vitro Fertilization-Embryo Transfer (IVF-ET) |
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Eggs (oocytes) are harvested directly from the ovarian surface, most of the time with a needle connected to a suction pump. The needle usually is passed under ultrasonic guidance through the top of the vagina sequentially into each ovary. The normal position of the ovary is just above the top of the vagina, making egg harvesting by this approach a straightforward procedure. The oocytes, when mature, are surrounded by follicular fluid that makes visualization with the ultrasound quite definitive. The "retrieval" as it is called, may be preformed under local anesthesia and intravenous sedation or light general anesthesia. In the early days of IVF, before ultrasonic technology was well developed, the retrievals were preformed via laparoscopy in an operating suite. This approach is still used when pelvic anatomy precludes the vaginal route, or when laparoscopy is indicated for other reasons.
Fertilization takes place in a petri dish in the laboratory under strictly controlled conditions of sterility, temperature, humidity, and gas content within culture media. Most of the time this occurs by simply surrounding the eggs with sufficient numbers of sperm, either freshly obtained or thawed after having been stored in a liquid nitrogen. In cases where sperm function is sub optimal, it is possible to insert a single sperm into the egg using a microscope and micro manipulators in a process known as IntraCytoplasmic Sperm Injection (ICSI).
After fertilization has been achieved, the zygotes, as the early embryos are called, are incubated, generally from 3 to 5 days in the laboratory, in complex media that are altered to meet the rapidly changing nutritional needs. During this time the fertilized egg divides and the embryo starts its development.The next step is that of "embryo transfers", in which embryos are placed within the uterus by exposing the cervix and passing a thin catheter, usually under ultrasonic guidance, into the uterine cavity. This requires no local or general anesthesia.
Egg Donor Pregnancy |
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Pregnancies achieved via insemination with donated sperm have over a century of history in the United States, but it was not until oocytes could be collected easily and safely that egg donation was entertained as treatment for infertile women with absent or reduced ovarian function. Usually the menstrual cycles of the donor and recipient are synchronized by hormonal manipulation so that the uterine lining (endometrium) of the recipient will be receptive to embryo implantation. When this can not be achieved because of logistics or other reasons, the embryos can be frozen for placement at a later date. Egg donors can be known to the couple as a friend or relative of the infertile woman, or as an anonymous individual. In either case extensive screening and psychological counseling is recommended. Egg donor candidates have been obtained by direct contact, advertisement and through agencies supplying that service.
Gestational Carrier Pregnancy |
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Also known as "gestational surrogate pregnancy", this form of ART allows a woman with absent uterus, a reproductively incompetent uterus, or medical conditions that do not allow for a safe pregnancy to have a child with her genetic input, as the carrier is genetically inert from the developing fetus. By necessity, the process can not be conducted anonymously. The donor does not need to be related to either husband or wife; there are no immunologic considerations. Extensive psychological screening and counseling is necessary to insure a happy outcome for all 
those involved, which may include the carrier's husband and children. Carriers need to be in good health and are expected to have a favorable obstetric history. Here, the process is the converse of the egg donor pregnancy; eggs are retrieved from the genetic mother, fertilized by her mate and embryos are placed in the uterus of the carrier, after which the pregnancy proceeds without additional high technology.
Ovarian Stimulation |
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Normally, towards the end of each menstrual cycle, a cluster of eggs within the ovary, known as a "cohort," begins a maturation process. This proceeds into the next cycle where one becomes "the dominant follicle"(expect for cases of fraternal twins), so that only one oocyte fully matures at ovulation. It is possible to perform ART in a natural cycle, but timing of egg retrieval are unfavorable. Instead, human hormone in the form of follicle stimulating hormone (FSH) is given by injection, starting early in the menstrual cycle. This has the effect of allowing development of more than one mature follicle. During this "follicular phase" dosage is adjusted according to the results of serial testing, using blood tests for the estrogen levels, and ovarian ultrasound examinations, alone or in combination. Just before the most advanced follicles are thought to be mature according to estrogen levels.