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Assisted Reproductive Technologies (ART)

IN VITRO FERTILIZATION (IVF)

There are many factors that can prevent the union of sperm and egg resulting in infertility. These are reviewed in the page Infertility facts. Fortunately, assisted reproductive techniques such as IVF can help. IVF is a method of assisted reproduction in which a man's sperm and a woman's eggs are combined outside of the body in a laboratory dish. One or more fertilized eggs (embryos) may be transferred to the woman's uterus, where they may implant in the uterine lining and develop. Excess embryos may be cryopreserved (frozen) for future use. Initially, IVF was used to treat women with blocked, damaged, or absent fallopian tubes. Today, IVF is used to treat many causes of infertility, such as endometriosis and male factor, or when a couple's infertility is unexplained.

The basic steps in an IVF treatment cycle are ovarian stimulation, egg retrieval, fertilization, embryo culture, and embryo transfer. These are discussed in the following sections.

1) Ovarian Stimulation

During ovarian stimulation, also known as ovulation induction, medications or "fertility drugs," are used to stimulate multiple eggs to grow in the ovaries rather than the single egg that normally develops each month . Multiple eggs are stimulated because some eggs will not fertilize or develop normally after fertilization. The maximum number of embryos transferred are based on the patient's age and other individual patient and embryo characteristics. Since each embryo has a probability of implantation and development, the number of embryos to be placed is determined for each patient, taking into account the odds of achieving a pregnancy based on the number of embryos transferred weighed against the risk of multiple gestation.

Medications used for Ovarian Stimulation

Oral:

Clomiphene citrate and letrozole (Femara) are administered orally while all the other medications are given by injection. Clomiphene citrate is less potent than injectable medications and is not as commonly used in ART cycles. There is no evidence that one injectable medication is superior to any other.

Gonadotropin Injections:

  • follicle stimulating hormone (FSH) (Follistim™, Gonal-F®, Bravelle™)
  • human menopausal gonadotropins (hMG) (Humegon™, Repronex™, Menopur®)
  • luteinizing hormone (LH) (Luveris®)

Medications for Oocyte Maturation and trigger release of the egg:

  • human chorionic gonadotropin (hCG) (Profasi®, APL®, Pregnyl®, Novarel™, Ovidrel®)

Medications to Prevent Premature Ovulation::

  • GnRH agonists (Lupron® and Synarel®)
  • GnRH antagonists (Antagon®, Ganarelix® and Cetrotide®)

Timing is crucial in an IVF cycle. The ovaries are evaluated during treatment with vaginal ultrasound examinations to monitor the development of ovarian follicles. Blood samples may be drawn to measure response to ovarian stimulation medications. Normally, estrogen levels increase as the follicles develop, and progesterone levels are low until after ovulation.

Using ultrasound examinations and blood testing, the physician can determine when the follicles are appropriate for egg retrieval. Generally, eight to 14 days is required. When the follicles are ready, hCG or other medications are given. The hCG replaces the woman's natural LH surge and causes the final stage of egg maturation so the eggs are capable of being fertilized. The eggs are retrieved before ovulation occurs, usually 34 to 36 hours after the hCG injection is given.

Up to 20% of cycles may be cancelled prior to egg retrieval. IVF cycles may be cancelled for a variety of reasons, usually due to an inadequate number of follicles developing. Cancellation rates due to low response to the ovulation drugs increase with age, especially after age 35. When cycles are cancelled due to a poor response, alternate drug strategies may be helpful to promote a better response in a future attempt. Occasionally, a cycle may be cancelled to reduce the risk of ovarian hyperstimulation syndrome (OHSS).

Treatment with a GnRH agonist or antagonist reduces the possibility of premature LH surges from the pituitary gland, and thereby reduces the risk of premature ovulation. However, LH surges and ovulation occur prematurely in a small percentage of ART cycles despite the use of these drugs. When this occurs, since it is unknown when the LH surges began and eggs will mature, the cycle is usually cancelled. Collection of eggs from the peritoneal cavity after ovulation is not efficient.

2) Egg Retrieval

Egg retrieval is usually accomplished by transvaginal ultrasound aspiration, a minor surgical procedure that can be performed in the physician's office or an outpatient center. Some form of analgesia is generally administered. An ultrasound probe is inserted into the vagina to identify the follicles, and a needle is guided through the vagina and into the follicles. The eggs are aspirated (removed) from the follicles through the needle connected to a suction device. Removal of multiple eggs can usually be completed in less than 30 minutes. Some women experience cramping on the day of the retrieval, but this sensation usually subsides by the next day. Feelings of fullness and/or pressure may last for several weeks following the procedure because the ovaries remain enlarged. In some circumstances, one or both ovaries may not be accessible by transvaginal ultrasound. Laparoscopy may then be used to retrieve the eggs using a small telescope placed in the umbilicus.

3) Fertilization and Embryo Culture

After the eggs are retrieved, they are examined in the laboratory for maturity and quality. Mature eggs are placed in an IVF culture medium and transferred to an incubator to await fertilization by the sperm.

Sperm is separated from semen usually obtained by ejaculation or in a special condom used during intercourse. Alternatively, sperm may be obtained from the testicle or vas deferens from men whose semen is void of sperm either due to an obstruction or lack of production. Microepididymal sperm aspiration (MESA), percutaneous epididymal sperm aspiration (PESA), or testicular sperm extraction (TESE) may be effective methods to collect sperm for IVF.

Fertilization may be accomplished by insemination, where motile sperm are placed together with the oocytes and incubated overnight or by intracytoplasmic sperm injection (ICSI), where a single sperm is directly injected into each mature egg . In the United States, ICSI is performed in approximately 60% of ART cycles. ICSI is usually performed when there is a likelihood of reduced fertilization, i.e., poor semen quality, history of failed fertilization in a prior IVF cycle, etc.

Overall, pregnancy and delivery rates with ICSI are similar to the rates seen with traditional IVF. Genetic counseling is advisable before ICSI if inherited abnormalities are identified that may be passed from father to son.

Day1: Visualization of two pronuclei the following day confirms fertilization of the egg. One pronuclei is derived from the egg and one from the sperm. Approximately 40% to 70% of the mature eggs will fertilize after insemination or ICSI. Lower rates may occur if the sperm and/or egg quality are poor. Occasionally, fertilization does not occur at all, even if ICSI was used. Visualization of two pronuclei the following day confirms fertilization of the egg. One pronuclei is derived from the egg and one from the sperm. Approximately 40% to 70% of the mature eggs will fertilize after insemination or ICSI. Lower rates may occur if the sperm and/or egg quality are poor. Occasionally, fertilization does not occur at all, even if ICSI was used.

Day 2: Two days after the egg retrieval, the fertilized egg has divided to become a 2-to- 4-cell embryo.

Day 3: A normally developing embryo will contain approximately 6 to 10 cells.

Day 5: A fluid cavity forms in the embryo, and the placenta and fetal tissues begin to separate. An embryo at this stage is called a blastocyst

Embryos may be transferred to the uterus at any time between one to six days after the egg retrieval. If successful development continues in the uterus, the embryo hatches from the surrounding zona pellucida and implants into the lining of the uterus approximately six to 10 days after the egg retrieval.

Assisted hatching (AH) is a micromanipulation procedure in which a hole is made in the zona pellucida just prior to embryo transfer to facilitate hatching of the embryo. Although AH has not been demonstrated definitively to improve live birth rates, AH may be used for older women or couples who have failed prior IVF attempts. There is no clear benefit of AH to improve pregnancy or live birth rates in other groups of IVF patients.

Preimplantation genetic diagnosis (PGD) is performed at some centers to screen for inherited diseases. In PGD, one or two cells are removed from the developing embryo and tested for a specific genetic disease. Embryos that do not have the gene associated with the disease are selected for transfer to the uterus. These procedures require specialized equipment and experience. The benefit of screening the embryos for disease in couples at risk and reducing the risk of having an affected child or terminating a pregnancy is preferable to some couples. While PGD can reduce the likelihood of conceiving a pregnancy with an affected child, it cannot eliminate the risk. Confirmation with chorionic villus sampling (CVS), amniocentesis or other testing is still necessary.

4) Embryo Transfer

The next step in the IVF process is the embryo transfer. No anesthesia is necessary, although some women may wish to have a mild sedative. The physician identifies the cervix using a vaginal speculum. One or more embryos suspended in a drop of culture medium are drawn into a transfer catheter, a long, thin sterile tube with a syringe on one end. The physician gently guides the tip of the transfer catheter through the cervix and places the fluid containing the embryos into the uterine cavity. The procedure is usually painless, although some women experience mild cramping.

ASRM issues guidelines regarding determination of how many embryos should be considered for transfer. The number of embryos transferred is largely based on the age of the woman or oocyte donor undergoing an IVF retrieval. These guidelines were created in order to help maintain the high success rates while decreasing the number of higher order multiple pregnancies (triplets and higher). Dr.Nagamani will discuss this with you prior to the transfer.

Cryopreservation of Embryoes

Extra embryos remaining after the embryo transfer may be cryopreserved (frozen) for future transfer. Cryopreservation makes future ART cycles simpler, less expensive, and less invasive than the initial IVF cycle, since the woman does not require ovarian stimulation or egg retrieval. Once frozen, embryos may be stored for several years. However, not all embryos survive the freezing and thawing process, and the live birth rate is lower with cryopreserved embryo transfer. Couples should decide if they are going to cryopreserve extra embryos before undergoing IVF.

DONOR SPERM, EGGS, AND EMBRYOS

IVF may be done with a couple's own eggs and sperm or with donor eggs, sperm, or embryos. A couple may choose to use a donor if there is a problem with their own sperm or eggs, or if they have a genetic disease that could be passed on to a child. Donors may be known or anonymous.

Donor Sperm:

In most cases, donor sperm is obtained from a sperm bank. Sperm donors undergo extensive medical and genetic screening, as well as testing for infectious diseases. The sperm are frozen and quarantined for six months, the donor is re-tested for infectious diseases including the AIDS virus, and sperm are only released for use if all tests are negative. Donor sperm may be used for insemination or in an ART cycle. Overall, the use of frozen sperm rather than fresh sperm does not lower success rates.

Donor eggs:

This is an option for women with a uterus who are unlikely or unable to conceive with their own eggs. Egg donors undergo the same medical and genetic screening as sperm donors, although it is not currently possible to freeze and quarantine eggs like sperm. The egg donor may be chosen by the infertile couple or the ART program. Egg donors assume more risk and inconvenience than sperm donors. In the United States, egg donors selected by ART programs generally receive monetary compensation for their participation. Egg donation is more complex than sperm donation and is done as part of an IVF procedure. The egg donor must undergo ovarian stimulation and egg retrieval. During this time, the recipient (the woman who will receive the eggs after they are fertilized) receives hormone medications to prepare her uterus for implantation. After the retrieval, the donor's eggs are fertilized by sperm from the recipient's partner and transferred to the recipient's uterus. Egg donation is expensive because donor selection, screening, and treatment add additional costs to the IVF procedure. However, our high live birth rate of greater than 50% with donor eggs provides many couples with best chance for success.

Donor embryos:

Some IVF couples to donate their unused frozen embryos to other infertile couples.

The use of donor sperm, eggs, or embryos is a complicated issue that has lifelong implications. If the couple knows the donor, both the couple and the donor should speak with a counselor and an attorney and have an attorney to file paperwork for the couple.