Infertility: In vitro fertilization and egg transfer (IVF-ET)

INFERTILITY

Infertility

In vitro fertilization and egg transfer (IVF-ET)

Introduction

Conception depends on a woman releasing an egg each month. The egg enters the fallopian tube where it meets the sperm. A sperm cell penetrates the egg, a process known as fertilization. The resulting embryo is transported down the tube to the uterus where it implants into the uterine lining (endometrium) a few days thereafter.

In general 75% of couples will achieve a spontaneous pregnancy within six months of exposure, 90% by a year and 95% by two years. Three major factors determine the chances of a natural conception; female age, sperm quality and duration of exposure.

IVF involves four basic steps; ovarian stimulation, egg recovery, insemination and finally embryo replacement.

Couples with less than two years exposure, need only consider IVF with proven tubal disease, significant semen abnormalities and moderate to severe endometriosis. Couples with unexplained infertility of less than two years, in women less than 35 need only to consider IVF after two or more years of trying and after a year in women older than 35.Minimal endometriosis is unlikely to be the cause of a delay in conception.

Although IVF was originally devised for women with tubal damage or dysfunction, in combination with intracytoplasmic sperm injection (ICSI) is a very effective method to treat male factor infertility. With ICSI a single sperm is selected by the biologist and injected into the egg. Surgical sperm retrieval may also be necessary with IVF/ICSI in men with absent or obstructed ducts. IVF treatment may be used in selected instances with donated eggs, sperm or embryos.

Selection of an IVF clinic. The published live birth rate per cycle started, at various clinics should be treated with great caution.

Patient selection ultimately determines the live birth rate for IVF. Couples need to be aware of the population treated by a centre as those able to select younger women with a short duration of infertility having their first treatment cycle are more likely to report better results

It is important to establish the cause of infertility before proceeding to IVF. Investigations would usually include checks of ovulation, tubal patency and an ultrasound for the female partner. A semen analysis is required for the male partner.

Transport IVF

Some IVF clinics work in conjunction with local hospitals to provide a more convenient treatment option for patients. Ovarian stimulation, monitoring and egg collection takes place at a hospital close to the patient's home. The eggs are then taken in a portable incubator to the licensed IVF clinic where fertilization and subsequent embryo transfer takes place.

Management of an IVF/ET cycle

Ovarian stimulation

During a natural unstimulated cycle, a follicle containing a single egg develops to maturity and it is therefore necessary to stimulate the ovaries with a group of drugs known as gonadotrophins. . The clinic should given you written information about these drugs and their side effects. Your GP can also explain how each drug works and their side effect, (plus see the Infertility Network UK factsheet on Problems with Ovulation)

Ovarian hyperstimulation (an excessive response) is the major and potentially life threatening complication associated with gonadotrophins. Couples should consider treatment in centers with low rates of OHSS. It is safest to monitor the response of the ovaries by daily oestrogen measurements and ultrasound Ultrasound scans are used to see the number and size of the follicles and to judge when to do the egg recovery. The oestrogens are necessary to determine the ovarian response. to stimulation. By interpreting the results of ultrasound and estrogen, the specialist will determine the best time to perform the egg collection. About 36 hours before the egg collection is due, an injection of human chorionic gonadotrophin (hCG) is given to initiate the final process of egg maturation. Precise timing is necessary as the eggs will be suitable for recovery 34 to 36 hours after the hCG injection.

Egg collection

This is done under sedation or general anesthetic using a vaginal ultrasound probe. u A needle is guided through the top of the vagina into the ovary. Each follicle is aspirated through the needle using a suction device.

Insemination and fertilization

The eggs are identified in the laboratory and placed in culture medium. They are then placed in dishes in an incubator. The male partner produces a semen sample by masturbation and this is prepared in the laboratory. A number of motile sperm are extracted and used to inseminate the eggs some hours later. It takes about 18 hours for fertilisation to be completed and about 12 hours later the embryo starts to divide. Two or three days after egg collection, when the embryos have reached the 2 - 6 cell stage, they are ready to be replaced into the woman's uterus.

Embryo transfer

This is a most important step and is best performed under ultrasound guidance. The procedure is virtually painless. . A maximum of two embryos may be replaced. Couples should consider the replacement of a single embryo to prevent a twin pregnancy. There is no evidence that bed rest makes a difference to the outcome and most units’ recommend resuming normal activities.

Luteal support

Hormone supplementation in the form of hCG injections, progesterone pessaries or injections are usually recommended after embryo transfer to support the uterine lining.

Embryo freezing

Most IVF clinics offer embryo freezing and storage for spare embryos. However, not all surplus embryos are suitable for freezing, not all survive the procedure and the implantation rate after transfer is lower than with fresh embryo transfer.

Abandoned cycles

The abandoned cycle rate varies considerably between different units. Cycles may be abandoned before egg recovery as the ovarian response is either inadequate or excessive, and before embryo replacement if no eggs are recovered or the eggs fail to fertilise or the embryos don’t divide. In many instances it will be possible to try again using alternative drugs or methods e.g. ICSI for failed fertilization.

Occasionally IVF cycles are abandoned because of a high risk of ovarian hyperstimulation. The risk of ovarian hyperstimulation is increased in women with polycystic ovaries.). In these circumstances the cycle may be cancelled during ovarian stimulation and restarted with a lower dose of drugs or allowed to proceed but all the embryos are frozen and replaced when the ovaries have returned to normal.

The ovarian hyperstimulation syndrome is potentially life threatening. This syndrome occurs in about 2 to 3% of cases and consists of severe nausea and vomiting, a rapid gain in weight, abdominal swelling and shortness of breathe. The fluid and electrolyte imbalance needs careful management in experienced centers. It starts a week after the hCG injection and is made worse by pregnancy.

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