Egg Fertilization and Embryo Transfer

Fertilization and Transfer

The fertilization of eggs and transfer of embryos can be accomplished by several means. The following descriptions are complete as of the publishing of this Web page.

In vitro fertilization (IVF) involves ovarian stimulation and egg retrieval. Shortly before egg retrieval, a semen sample is collected. The retrieved eggs are placed in a laboratory dish with the motile sperm, where fertilization takes place. The fertilized eggs develop from 3 to 5 days in a special culture medium in a controlled environment, and are then transferred to the woman's uterus for potential implantation and embryo development.

Intracytoplasmic sperm injection (ICSI) is an effective treatment for male infertility. Following egg retrieval, a single sperm is injected into each egg. It is also possible to aspirate sperm directly from the epididymus or testicles, thereby making ICSI an option for men who have had vasectomies or men with congenital absence of the vas deferens.

Gamete intrafallopian transfer (GIFT) is similar to IVF, but with fertilization taking place inside the woman's own body. Following ultrasonically guided retrieval, the eggs are mixed with sperm and transferred immediately into the fallopian tube via laparoscopy. For patients with at least one normal fallopian tube, GIFT may be an option.

Zygote intrafallopian transfer (ZIFT), another variation of IVF, involves transferring pre-embryos into the fallopian tubes just 24 hours after in vitro fertilization. At this stage, the fertilized eggs are called zygotes. Similarly, tubal embryo transfer (TET) also involves the laparoscopic transfer of embryos 1 to 3 days after retrieval.

Assisted hatching involves laboratory manipulation of the embryo to create an opening in its outer covering (zona pellucida). This technique may increase the chance of implantation, especially in reproductively older women.

Blastocyst transfer (BT) is a technique introduced here at Stanford in 1998 by our embryologists and physicians. As with IVF, the eggs are retrieved from stimulated ovaries, fertilized, and allowed to develop for 2-3 days in cleavage medium. The embryos are then transferred to blastocyst medium for 2 additional days before being transferred to the woman's uterus.

During those crucial days, the embryos undergo key developmental changes that help to determine which are most likely to survive. The extra days also allow for further enrichment of the uterine lining, increasing the chances for successful implantation. Physicians transfer fewer embryos, called blastocysts at this stage, thereby reducing the chance for multiple births. Success rates for blastocyst transfer are encouraging.

Cryopreservation allows surplus embryos to be stored for later use. In addition, if the uterine lining is not suitable for implantation in a stimulated cycle, cryopreservation allows transfer during a different menstrual cycle. Women facing medical procedures affecting fertility can also use cryopreservation to bank embryos for the future.

The donor oocyte (egg) program offers hope for women with difficulty in egg production or whose eggs carry a genetic defect. Click here to access information about our egg donation program, as well as our Oocyte Donor Personal History form.

Preimplantation Genetic Diagnosis (PGD) is designed for patients requiring genetic screening of embryos. It can be used to detect whole chromosome abnormalities such as those leading to Down's Syndrome or recurrent miscarriage. PGD can also be used to detect single gene disorders, for example: cystic fibrosis, thalassemia, anemias, etc. Specific applications should be discussed with your physician and genetic counselor.  See the Fertility and Reproductive Medicine Clinic's resources page for links to several genetics laboratories.

Our laboratory is accredited by the College of American Pathologists and the American Association of Bioanalysts. We have a California tissue bank license and are registered with the Food and Drug Administration.

See our study: Picking good eggs