In-Vitro   Fertilization Overview Blastocyst Transfer ICSI PGD IVF Success Rates   Donor Egg   Program Overview Information for Donors Questions and Answers Success Rates Satellite Offices

Blastocyst Transfer

Normally, fertilization of the egg occurs in the fallopian tube where the embryo spends three days developing to the 8-cell stage. This embryo then travels into the uterine cavity where it grows to a blastocyst (140 cells) by day 5 (photo). At this point, on either day 5 or day 6, the embryo breaks through the outer membrane (hatching) and attaches to the wall of the uterus where it continues to grow into a baby.

Prior to 1998 most IVF programs transferred three to four embryos on day 3 at the 8-cell stage. Unfortunately (or fortunately), the incidence of triplet pregnancies became unacceptably high, accounting for 10 to 15% of pregnancies. Fortunately, a technique which divided the culture process into two steps was developed by Dr. David Gardner, permitting IVF laboratories to grow embryos to day 5 and thus transfer only two embryos while maintaining high pregnancy rates without the risk of triplet pregnancies or greater.

Blastocyst transfer was introduced into our program in September of 1998 and during the interval of late 1998 through March of 1999 70% of embryo transfers were performed on day 5. There were no triplet pregnancies in the blastocyst transfer group and only one in the day 3 group. This information has been published. Not all patients will have a blastocyst transfer, however, and we prefer to select the day of transfer based on the judgment of our embryologist regarding the best chance of a singleton or twin pregnancy.