The field of assisted reproduction is continually changing and this is a good thing because, for the most part, these changes have been for the better. Better medications, improved treatment strategies and a better understanding of laboratory techniques are resulting in constantly improving embryo implantation rates. This will allow us to transfer fewer embryos, reducing the risks for twins or triplets, which will result in better obstetrical outcomes for our patients. Our goal in assisted reproduction is to do all we can to ensure that chromosomally normal embryos have the opportunity to result in a healthy pregnancy.
More and more, Pacific Fertility Center is utilizing the day-5 embryo transfer procedure. The benefits of this are to 1) improve implantation and pregnancy rates and 2) lower the number of embryos transferred. Allowing embryos to remain in the laboratory for 5 days after egg retrieval (as opposed to the more standard 3 days) gives us an opportunity to choose those embryos most likely to carry normal chromosomes and those most likely to keep developing in the womb after embryo transfer. PFC utilizes low oxygen incubators almost exclusively. As such, we are seeing an improvement in the percentage of embryos that are developing well in the lab environment, as evidenced by their continued progression from a cleavage stage embryo to a blastocyst stage embryo. Although Day-5 embryo transfer has been around for a while, we have been hesitant to use it exclusively for our patients. Clinical data suggests that unless a woman has a good number of nice looking embryos on day 3, the risks of having no well developed embryos on day 5 is fairly high. Therefore, the patient choosing to attempt a day-5 transfer might end up with virtually no embryos to transfer.
One argument asserts that this is what would probably occur within the uterine lining anyway. However, there are studies suggesting that pregnancy rates in women with less than three or four nice 8-cell embryos on day 3 will have a higher chance of pregnancy with a day-3 transfer as compared to women with less than three or four nice 8-cell embryos who have a day-5 transfer. We are noticing that, with the use of our new low oxygen incubators, we are getting better developed embryos on day 3. These embryos, in turn, have a greater chance of being a nice embryo on day 5. We are also seeing a small but growing number of couples interested in the transfer of only one embryo because they wish to avoid the risks of having a twin pregnancy. Although the over-whelming majority of babies born as a twin do well, there is a measurable increase in the incidence of perinatal death and cerebral palsy in twins as compared to babies born as a singleton. Also, we have many patients returning to us for baby #2 or #3 and they would like to avoid a multiple gestation. This has been particularly true for our patients using donor egg-derived embryos.
Last year, we saw a 50% pregnancy rate in women electively transferring one embryo in the donor egg program. We will definitely support any patient that wishes to transfer only one embryo at a time, and we will likely encourage day-5 transfers to better select the one embryo most likely to implant. One potential downside of attempting day-5 transfer is the question of whether or not we will increase the number of pregnancies in the fresh IVF cycle at the expense of additional attempts with frozen embryos. This is because embryos frozen at a cleavage stage [day 3] have historically done better with freezing and thawing as compared to day-5 embryos. Pacific Fertility Center has always had a strong freezing program with excellent success rates with frozen embryo transfers, mostly at the day-3 stage of freezing and thawing.
Many patients have asked us why we do not freeze some embryos at day 3 and culture some to day 5. One reason is that when we freeze some embryos at day 3, we are taking them out of contention for fresh embryo transfer and therefore, we may be losing some of the selective advantage of doing a day-5 transfer. With patients that have a very large number of embryos on day 3 that look good (say 15 or more), this may still be a viable strategy. Most patients don't have many good quality cleavage stage embryos, however. So when we are planning to attempt a day-5 transfer, we will usually plan to culture all embryos to day 5 and select the best one or two for transfer and freeze the remainder as a day-5 embryo. As a result, we are now seeing a larger number of our patients returning for frozen embryo transfer with their day-5 frozen embryos.
Our laboratory director, Dr. Joe Conaghan is currently reviewing the data on implantation rates from frozen-thawed day-5 embryos from 2005. Listed below are some of the situations for which we are more likely to recommend a day 5 transfer. These include: 1. Any woman undergoing transfer with donor egg-derived embryos (anonymous donors) 2. Any woman less than 40 with a large number of eggs/embryos/good quality day 3 embryos 3. Any woman that has had poor success with freezing and thawing on day 3 in prior ART cycles 4. Any patient considering transferring only one embryo 5. Any patient with a history of multiple ectopic pregnancies (one recent abstract from the ASRM meeting suggested a decrease in the ectopic rate after IVF with a day 5 vs. day 3 embryo transfer). 6. Any woman with unexplained IVF implantation failures with day-3 transfer. -- Carolyn Givens, MD Related Posts: Low O2 Incubators Stages of Embryo Development From Egg to Blastocyst Day 3 vs. Day 5 Transfer - Photos