In Vitro Fertilization (IVF)
In Vitro fertilization, or IVF, is a method in which egg cells, taken from the principal patient or from a donor, are fertilized outside the woman's body, and upon attaining a certain level of growth, implanted inside the uterus.
A generic term referring to the test tubes in laboratory practices gave this procedure its name; "In vitro" is Latin for "in glass" though in practice, neither glass nor test tubes are used. However, popularly, babies that are the result of IVF have been called "test tube babies".
IVF is often considered the last and most successful option in modern conception techniques. When all other methods of achieving conception fail, IVF is a major treatment in infertility.
There are many factors that determine success rates including the age of the patient, the quality of the eggs and sperm, the duration of infertility, the health of the uterus, and medical expertise. The chance of a successful pregnancy using IVF treatment is approximately 20-30% for each IVF cycle, although some clinics using better procedures and monitoring environments are now able to quote rates up to 50% per cycle.
The IVF process has six major steps:
1] Ovarian stimulation: Doctors stabilize and control the ovulatory process of the patient thereby inducing egg production for the next phase. Fertility medications are administered to stimulate the controlled development of multiple follicles of the ovaries, usually around the third day of menstruation, all under very close monitoring. When the follicles are adequately mature, hormonal agents are given to the patient that result in ovulation within 36 hours.
2] Oocyte Retrieval: this procedure involves removing the eggs (ova) from the patient’s ovaries. Doctors use a transvaginal technique, combining ultrasound-guided needles piercing the vaginal wall to reach the ovaries. Using this needle, follicles are aspirated, and the follicular fluid is handed to the IVF laboratory to identify ova (eggs). The retrieval procedure takes about 20 minutes.
3] Selecting/Harvesting sperm from the partner/donor: Semen provided by the male partner is prepared for fertilization by removing seminal fluid and inactive cells.
4] Incubated culture fertilization OR Intra-cytoplasmic sperm injection (ICSI): These are two separate processes used depending on the quality of sperm received from the male donor. Incubated culture fertilization involves the sperm and the egg being incubated together, at a ratio of about 75,000:1 in the culture media for about 18 hours. By that time, if the fertilized egg shows two pronuclei, then fertilization has taken place. In situations where the sperm count is low, Intracytoplasmic sperm injection (ICSI) is used where a single sperm is injected directly into the egg using micromanipulators like microinjections and micropipettes. The fertilized egg is passed to a special growth medium and left for about 48 hours until the egg has reached the 6-8 cell stage.
5] Embryo Transfer: Transferring the zygote (fertilized egg) or a more mature embryo to the patient's uterus. The embryos judged to be the "best" are transferred to the patient's uterus through a thin, plastic catheter, which goes through her vagina and cervix. Often, several embryos are passed into the uterus to improve chances of implantation and pregnancy.
6] Post-transfer and Establishing Pregnancy: A successful pregnancy occurs when a zygote or embryo attaches itself to the uterine wall. The patient has to wait two weeks before she returns to the clinic for the pregnancy test. During this time she may receive additional medications like progesterone, a hormone that keeps the uterus lining thickened and suitable for implantation.
Risks and complications
One major complication associated with IVF is that of multiple births. During the embryo transfer phase, to ensure a successful pregnancy, doctors transfer multiple embryos in the hope of at least one successfully attaching itself to the uterine wall. Multiple births are correlated with obstetrical complications, premature births, increased risk of pregnancy loss and neonatal morbidity with the potential for long term damage. Some countries like England impose strict limits to the number of embryos that may be transferred to reduce the risk of high-order multiples (triplets or more). Experts in the field often debate these limits and hence, the guidelines are not universally followed or accepted. Spontaneous splitting of embryos in the womb after transfer, leading to identical twins does occur, but is rare (under 1% of all IVFs). Recent evidence suggests that if a woman is conceiving a single offspring post IVF treatment, the offspring is at a higher risk of low birth weight. Reasons for this are unknown.
Another complication of IVF is of the development of ovarian hyperstimulation syndrome during the ovarian stimulation phase. Symptoms of patients with hyperstimulation are weight gain, edema and abdominal distention and pain and, in extreme cases, difficulty in breathing.
The issue of birth defects remains a controversial topic in IVF. A majority of studies do not show a significant increase after use of IVF. Some studies suggest higher rates for ICSI, while others do not support this finding. Major birth defects include chromosomal abnormalities, genetic imprinting defects, and multiple organ abnormalities. A systematic review conducted by Hansen, of published studies (including ICSI) found a 30-40% increase risk of birth defects associated with assisted reproductive technology when compared to children born after spontaneous conception. Possible explanations offered were the underlying cause of the infertility, factors associated with IVF/ICSI, culture conditions, and medications. However, as of now, the actual cause is not known.