The IVF Process

In vitro fertilization (IVF) is what comes to mind for most people when they think about fertility treatments. This is not surprising given the increasing use of IVF over the last ten years.

The basic premise of all assisted reproductive technology (ART) is that the fertilization process (union of the sperm and egg) and embryo transfer process (placement of the embryo into the uterus) is aided by a clinic laboratory. The IVF technique was initially designed for treatment of women with tubal infertility since in IVF the fallopian tubes are bypassed entirely. Eggs are retrieved from the body and inseminated in a lab with semen from a partner or a donor. Once fertilized, embryos are transferred to the uterus in a second procedure.

Egg Retrieval

Medications that help stimulate the ovaries to produce mature eggs for retrieval in IVF typically include drugs for controlled ovarian hyperstimulation (i.e. gonadotropins), drugs to prevent premature ovulation (i.e. GnRH antagonists), and drugs to mature the eggs (hCG).

You should discuss the medication options with your healthcare provider and have a clear understanding of when you start and stop each medication.

Egg retrieval is performed about 36 hours after the eggs are triggered to mature with human chorionic gonadotropin (HCG). Some form of analgesia is administered, and the eggs are usually removed by ultrasound-guided retrieval or, less commonly, by laparoscopy. The eggs and surrounding fluid are aspirated into a needle that is then given to the embryology lab (see below).

There are risks related to the procedure, as with any surgery that requires anaesthesia (if needed). Regardless of whether guided ultrasound or laparoscopy is used, use of the needle for aspirating the eggs has a slight risk of bleeding, infection, and damage to the bowel, bladder or a blood vessel. Some women experience post-operative cramping which usually resolves by the day after retrieval. Additionally, because the ovaries have been stimulated and may be enlarged, some women may experience a feeling of fullness or pressure that may last for several weeks after egg retrieval.

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Fertilization

The embryologist looks for eggs in fluid removed from the follicles. The eggs are assessed for maturity and incubated. The male partner is asked to collect the sperm sample if fresh sperm is used. A semen analysis is performed and the sample is washed with a special solution of nutrients to isolate the more motile sperm. Fertilization is done in the lab. The exact process used depends on the type of infertility and the clinic used. In standard IVF, the sperm is placed into the dish containing the egg.

Clinics typically perform intracytoplasmic sperm injection (ICSI) primarily for reasons of severe male factor infertility. ICSI is a technique that is useful for severe male factor infertility. The sperm is collected in a needle and then injected directly into the egg.

  • Approximately 24 hours later, the embryologist can determine if fertilization has occurred.
  • In 24 to 72 hours, the embryologist can determine if the embryo is growing.

The sperm and eggs (oocytes) are placed in growth media containing special nutrients that allow them to live outside the body. The egg, when fertilized by sperm after 18-24 hours, becomes an embryo that is allowed to grow and divide in the laboratory for an additional 2-5 days in the special culture media.

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Embryo Transfer

Transfer usually occurs two to five days after fertilization depending on the number and quality of the embryos and the clinic policy. Healthcare providers will often transfer more than one embryo into the woman’s uterus to increase the chances of pregnancy. However the number transferred depends on the age of the woman, the quality of the embryos, and the success rates of the clinic. The current trend is to transfer one to two good embryos to reduce the risk of high order multiple pregnancy (triplets or more).

The embryo culture systems currently used allow the embryos to develop to the blastocyst stage (day 5) instead of days 2-3. This means that better quality embryos are transferred without compromising pregnancy rates. This also means that the risk of higher-order multiple pregnancy is reduced. On average 30% to 50% of the fertilized embryos will continue developing into blastocysts. Typically 1-2 embryos are transferred in women under 35, no more than 3 in women 35-39, and no more than 4 in women over 39.

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