In vitro means that the eggs are fertilized in a laboratory, as opposed to in vivo, in which the eggs are fertilized in the fallopian tube.
The process begins with the suppression of ovarian function via the administration of birth control pills. This allows for the development of several eggs at the same time.
Next, follicle-stimulating hormones (Gonadotropins) are used to stimulate egg development in the ovaries. Serial ultrasounds and hormone assessments are used to decide when the follicles have matured. Then an injection of HCG is given and about 34-36 hours later an egg retrieval is performed.
Using an ultrasound probe to produce images of the reproductive organs while the patient is under general anesthesia, eggs are gently extracted using a very fine needle.
After a brief maturation in the laboratory, the partner or donor sperm is introduced, and the eggs undergo in vitro fertilization.
There are two ways that an egg may be fertilized by IVF: traditional and ICSI. In traditional IVF, 50,000 or more swimming sperm are placed next to the egg in a laboratory dish. Fertilization occurs when one of the sperm enters into the cytoplasm of the egg. In the ICSI process, a tiny needle, called a micropipette, is used to inject a single sperm into the center of the egg. With either traditional IVF or ICSI, once fertilization occurs, the fertilized egg (now called an embryo) grows in a laboratory for 1 to 5 days before it is transferred to the woman’s uterus.
The fertilized eggs are cultured for a period of five days before the strongest are selected for transfer to the uterus. Some prospective parents will choose to have preimplantation genetic screening performed prior to embryo transfer in order to select healthy embryos.
The day of the embryo transfer the embryos are evaluated once again. Based on their grading, a recommendation for which ones and how many embryos to transfer is done and discussed with the couple. Embryos are inserted into the uterus using a catheter via the cervix. All of the embryos that are to be transferred are loaded into the transfer catheter. Under ultrasound guidance, they are placed 1 to 2 cm from the top of the uterine cavity.
Post-procedure, the catheter is checked to ensure there are no retained embryos.
The usual number of embryos transferred depends on a number of factors, including maternal age, the number of oocytes retrieved and availability of embryos for cryopreservation. We follow The American Society for Reproductive Medicine current guidelines on how many embryos to transfer.
When there are embryos in excess after the embryo transfer, they can be cryopreserved for future use.
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