IVF differs from “natural fertilization” because the union of the egg and sperm (fertilization) occurs in a Petri dish rather than in the body, at the end of the fallopian tube. The term “in vitro” literally means “outside of the body”.
A successful IVF cycle requires that several steps be completed.
IVF requires numerous eggs compared to a natural cycle which only requires one. This is because some of the eggs used in an IVF cycle will be damaged during the ART procedures and others will not fertilize and develop.
To produce the number of eggs needed for IVF, and to appropriately time egg release, IVF patients are started on fertility drugs (Lupron, Antagon, Cetrotide) designed to suppress their own hormones (FSH and LH). FSH is administered by injection and directly stimulates the ovaries to recruit and develop numerous follicles, each of which contains an egg. Drugs like Lupron are critical to a successful cycle as they “block” natural ovulation. Otherwise, ovulation may occur prior to egg retrieval resulting in a “lost IVF cycle”. While on these drugs, ovulation must be induced by the drugs hCG or LH.
The progress of the IVF cycle is monitored by ultrasound scans of the ovary. Northwell Health Fertility’s IVF program has the latest monitoring equipment. As the follicles develop, the number and size can be measured using transvaginal ultrasound. As healthy follicles develop in an IVF cycle they produce increasing levels of estrogen, which is monitored by blood tests. Estrogen levels are used to help determine the appropriate dosage of FSH and to avoid potential side effects, such as ovarian hyperstimulation syndrome.
Once the follicles, developed during the IVF cycle, are judged to be mature, an injection of hCG is given to initiate the final phase of egg development. Sufficient development and an adequate number of eggs must be present in order to proceed to retrieval.
Oocyte (Egg) Retrieval
IVF oocyte retrieval is performed using intravenous sedation. A needle is inserted under ultrasound guidance through the vagina into the follicle on the ovary. The follicles, containing the eggs, are punctured and aspirated. If the procedure is successful, one or more of the eggs will be obtained.
Sperm are usually obtained by masturbation the same day. The eggs are inseminated with the processed sperm and fertilization is allowed to take place. Micromanipulation of the sperm and egg is sometimes required to achieve fertilization (ICSI – intracytoplasmic sperm injection).
Allowing the embryos to grow in an environment established by culturing other cells from the woman sometimes improves the quality of the embryos (co-culture).
Sometimes the sperm count, or quality are poor (male infertility) and an adequate sample cannot be obtained by masturbation. In some of these cases, the sperm may be withdrawn directly from the testicles (TESA) or other parts of the male reproductive tract (MESA).
Intracytoplasmic sperm injection, ICSI, is often employed in case of male infertility. Using ICSI, a single sperm is injected into each egg. ICSI can be performed with extremely small quantities of ejaculate or sperm retrieved from the reproductive track.
Once the embryos mature, a number (determined by the fertility specialist, embryologist, and patient) of them are inserted through the cervix into the uterus by means of a small catheter.
In some IVF cycles, prior to transfer, some or all of the embryos may undergo assisted hatching to increase implantation rates. The embryo transfer is usually painless and no sedation is required. Most IVF patients will be given drugs, such as progesterone, after the embryo transfer to insure endometrial development.
Excess embryos may be frozen for possible transfer in a future cryopreserved IVF cycle. While cryopreserved IVF cycles produce lower success rates compared to fresh IVF cycles, their cost is much lower. This is because the embryos have already formed and their is no need for ovulation induction drugs or embryo culturing.
Northwell Health Fertility’s success rates significantly exceed the national averages. Success rates for US clinics can be reviewed at the Centers for Disease Control Web site. However, be careful when comparing IVF programs as the treatment populations may be different. For example, an IVF center that employs IVF on a large number of women under the age of 30 will appear to have better success rates than a clinic that treats an excess of women 35 yrs. of age and older. There is a direct correlation between female age and IVF success rates.