Women also face an increased risk of severe complications in pregnancy. Therefore, any action that can be taken to minimize the incidence of multiple pregnancy without compromising the likelihood of conceiving would clearly be beneficial to both mothers and their infants.
As part of the IVF procedure, multiple embryos have traditionally been transferred to the uterus in an effort to increase the chances of a successful pregnancy. The Society for Assisted Reproductive Technology (SART) currently recommends transfer of no more than four embryos for patients aged 35 to 40 and two embryos for patients younger than age 35.
While these recommendations provide a maximum for clinicians to follow, improved technologies have enabled increased pregnancy rates while minimizing the risk for multiples.
A study recently completed at the Colorado Center for Reproductive Medicine under the direction of William B. Schoolcraft, MD, the Center's medical director, demonstrated the risk for multiples can be virtually eliminated in appropriate IVF patients. This research evaluates the efficacy of transferring a single blastocyst stage embryo in an effort to prevent multiple pregnancies while maintaining high ongoing pregnancy rates.
In this trial, the first prospective randomized study of its kind, 48 patients undergoing IVF who were candidates for blastocyst embryo transfer were randomized to transfer of one or two embryos five days after egg retrieval. After fertilization, embryos were cultured to the blastocyst stage in the laboratory using advanced culture techniques. A remarkable 60.9 percent ongoing pregnancy rate was achieved in women undergoing transfer of only a single embryo with no twins. The ongoing pregnancy rate in those receiving two embryos was 76 percent.
This latest research employs technology developed at the Center which was awarded the prize paper at the American Society for Reproductive Medicine (ASRM) in 1998. Under the direction of David Gardner, PhD, scientific director at the Center, the original research demonstrated an increased likelihood of embryo implantation and pregnancy with the transfer of embryos grown in the laboratory for five days rather than the traditional three days, allowing the embryos to develop to the blastocyst (blast) stage of development. This enabled clinicians to successfully decrease the number of embryos required for transfer.
This research represents a significant advance in treatment options available for infertile couples providing a high potential for conception while minimizing risks.