How Many Embryos can be Implanted for IVF?
Now that we have made it through the initial hurdles of IVF, we must now decide on when and how many embryos to transfer. In the past, the discussion centered around day 3 or day 5 transfer of fresh embryos. However, over the years, experience and data have demonstrated that the transfer of “Day 5” blastocyst stage embryos (80-100 cells) is significantly more successful than transfer of lesser developed embryos. Moreover, barring a few specific situations, pregnancy outcome is also significantly improved when embryos are transferred into a uterine lining that has not been overstimulated, as would be in the case of a fresh IVF cycle with ovarian stimulation and fresh embryo transfer. Therefore, the majority of successful fertility centers have migrated to the creation and freezing of blastocyst stage embryos followed by a frozen embryo transfer cycle after the woman’s body has recovered from the ovarian stimulation. In addition, preimplantation genetic testing of embryos (screening of embryos to select only those with normal chromosome numbers), if desired, occurs at the blastocyst stage and makes the freezing and subsequent frozen embryo transfer necessary.
Embryos transferred at the blastocyst stage have made it through key growth processes and typically offer a greater chance of implanting. In addition, the blastocyst can also be graded based on level of appropriate growth and development and on the appearance of the inner cell mass (future fetus), trophoblast (future placenta), and cavity. Due to the significant improvement in embryo quality and implantation rates, in most cases, we need only return 1 single blastocyst into the uterus at a time, greatly reducing the risk of multiple pregnancy without compromising the pregnancy success rate. A significant benefit of blastocyst culture and transfer is the reduction of multiple births that can result from in vitro fertilization. This means that the many obstetrical complications that may arise from multiple pregnancies can be minimized. It is especially important in helping patients avoid having to make the difficult personal and ethical decisions regarding selective reduction.
Single Embryo Transfer
At the Mesa, Scottsdale and Phoenix AZ offices of Advanced Fertility Care, our goal is to provide those seeking to start or add to a family with a single healthy child. One of the negative side effects of IVF is that of multiple pregnancies. Our own success data shows that at AFC, we are very successful at achieving pregnancies. In general, in the past, when two to three embryos were transferred, we had seen a twin pregnancy rate of approximately 40%. However, with the improvement in technique and with genetically normal embryos, that has been as high as 60%. In addition, our own internal data has also shown that for women under age 35 who have developed multiple high quality blastocysts, the implantation rate is well above 90% in our Center. This can be interpreted to mean that for those patients who have multiple high quality blastocysts on Day 5, they will be pregnant with however many blastocysts are transferred. It is for this patient population that we highly recommend a single blastocyst transfer. Can you have twins with a single embryo transfer? In rare cases the answer is yes, but by limiting the transfer to a single blastocyst, the overall success rate is only minimally decreased (less than 6%), while the risk of multiple pregnancy is reduced from ~ 60-70% down to 3-4% (the chance of one embryo splitting on its own after transfer). There are also certain circumstances such as congenital uterine anomalies, small maternal pelvis, or previous pregnancy complications that may mandate a singleton pregnancy in order to lower the risk for adverse effects on the mother.
Regardless of the circumstances, Drs. Zoneraich, Larsen and Kummer and our embryology staff will discuss the specifics of your case with you and provide you with our expert recommendations as to the number of embryo(s) that we recommend for transfer. As a member of the American Society of Reproductive Medicine and as a Center of Excellence for many of the third party insurance companies, this means abiding by current guidelines for safe and ethical practice in reproductive medicine which calls for the transfer of only one blastocyst at a time. In addition, in some cases where IVF treatment is being covered by a particular insurance company, the number of embryos permitted to be transferred is dictated by the covering insurance carrier.
What is a Frozen Embryo Transfer?
A frozen embryo transfer occurs when embryos derived in a prior IVF cycle are frozen at the blastocyst stage for future transfer into the prepared uterus. This process now accounts for the majority of the embryo transfers performed at Advanced Fertility Care. As mentioned previously, experience and research has shown that delaying transfer into the uterus when it is not “hyperstimulated” during ovarian stimulation is ideal for improving success rates and mimicking mother nature.
The frozen embryo transfer process itself involves ovarian suppression with oral contraceptive pills and leuprolide injections, followed by stimulation of the uterine endometrial lining using estrogen supplementation (in the form of skin patches, oral, or vaginal tablets) and progesterone (injections and/or vaginal formulations). The frozen embryo is then warmed and transferred into the uterus at the appropriate point in uterine stimulation. The survival rate of a frozen embryo to successful thaw is >95%.