How In Vitro Fertilization Works
The entire in vitro fertilization (IVF) cycle takes one to two months. The IVF and embryo transfer process follows these basic steps.
- Ovarian stimulation. The woman takes fertility medications to stimulate multiple eggs to grow in the ovaries rather than the single egg that develops normally each month. The medications also help control ovulation induction – the timing of egg maturation – to increase chances of collecting multiple eggs during one of the woman’s cycles. It is best to collect multiple eggs during the egg retrieval process because some eggs will not fertilize and others will not develop after fertilization. Timing is critical in an IVF cycle, so the ovaries are monitored closely for egg development using ultrasound, and blood samples may be used to check hormone levels.
- Egg retrieval. The woman’s eggs are retrieved through a minor surgical procedure called transvaginal aspiration, which uses ultrasound imaging to guide a hollow needle through the pelvic cavity. Sedation or local anesthesia is provided to remove any discomfort during the surgery. Multiple eggs can be removed in less than 20 minutes. Women commonly experience cramping on the day of retrieval, which usually subsides in a few days. The ovaries remain enlarged afterwards and a feeling of fullness or pressure may last for several weeks following the procedure.
- Sperm collection. The sperm used in the IVF procedure are usually obtained by ejaculation or collected in a special condom used during intercourse. The man is usually advised to abstain from ejaculating for two to three days before providing the sample in order to increase the sperm count and enhance pregnancy rates. If necessary, sperm may be obtained directly from a testicle or vas deferens from men whose semen is void of sperm either due to obstruction or lack of production. The sperm is separated from the semen and washed to prepare the sample for combining with the eggs.
- Insemination, fertilization, and embryo culture. During the insemination process, the sperm and eggs are placed together in an incubator overnight to enable fertilization to occur. If the possibility of low fertilization is suspected, intracytoplasmic sperm injection (ICSI) may be used, which injects a single, carefully selected sperm directly into the egg. The eggs are monitored to confirm that fertilization has occurred and that cell division is taking place. Once this occurs, the fertilized eggs are considered embryos. Approximately 40 to 70 percent of the mature eggs will fertilize in the incubator or after ICSI. Lower rates may occur if the sperm or eggs were of poor quality. Occasionally, fertilization does not occur at all, even with the use of ICSI.
- Preimplantation Genetic Diagnosis (PGD). In special cases, after embryos form, preimplantation genetic diagnosis (PGD) may be performed to screen for inherited diseases.
- Implantation. Most commonly, embryos are transferred into the woman’s uterus three to five days after egg retrieval. The transfer process involves a speculum that is inserted into the vagina to expose the cervix. A predetermined number of embryos are suspended in fluid and gently placed through a catheter into the womb, guided by ultrasound. The procedure is usually painless, but some women experience mild cramping.
- Pregnancy Testing. After the IVF process is complete, the woman can rest. A pregnancy test approximately two weeks later can confirm whether or not a pregnancy has occurred. Later, an ultrasound will be used to determine if the pregnancy is continuing to develop correctly.