Hello everyone – Dr. DiMattina here. For stimulated IVF, most of the premier IVF centers around the world now only transfer frozen thawed embryos (FET). Here’s why.
Stimulated IVF continues to rapidly evolve and especially so in the last 4 years. Traditionally, in a stimulated IVF cycle, embryos are produced and a fresh embryo transferred back into the uterus. Any extra embryos are cryopreserved and stored for later embryo transfer if needed. Well that has all changed.
Modern literature confirms that IVF pregnancy rates are superior when transferring frozen-thawed embryos as compared with fresh embryos. The data is overwhelmingly strong and FET should be the preferred method of embryo transfer for most if not all patients undergoing stimulated IVF. I include a few references below for those interested.
So what’s the problem with fresh embryo transfer in a stimulated IVF cycle? It has been well demonstrated that ovarian stimulation drugs have an adverse effect on the endometrium in about 40% of patients who are stimulated. This results in an unfavorable environment for the embryo for implantation, thereby decreasing the IVF pregnancy rate. By cryopreserving the embryos and later transferring an embryo in a non-stimulated cycle, the likelihood for embryo implantation is greatly increased. The embryo freezing process is most safe. At Dominion Fertility our embryo survival rate is about 97% and there are no increased risk for birth defects. FET is safe and results in a higher chance for pregnancy. What’s not to like?
Of note, I believe that FET is most important in those patients who produce only one or two embryos. In such a circumstance where few embryos exist, one would most definitely want to transfer the embryo in the most optimal environment possible using FET rather than transferring the embryo in a less than optimal setting with a fresh embryo transfer.
Can we make IVF even more successful? Absolutely, by adding preimplantation genetic screening (PGS). One of the greatest causes of an IVF failure is that the embryo is genetically abnormal. Because of advances in embryo biopsy, the embryo can now be tested with 99% accuracy to determine if it is genetically normal or not. By transferring only the genetically normal embryo, the implantation rate is even further increased and the chances of a spontaneous abortion greatly decreased. Last October, we published an abstract showing that a 41 year- old patient has the same implantation rate as a 30 year- old patient when a PGS genetically normal embryo is transferred. In other words, a 41year- old patient has the same probability of getting pregnant as a 30 year-old patient when undergoing stimulated IVF with FET and PGS. That’s great news for all patients!
Here is an example of a patient of mine who came for infertility care after she had previously experienced 3 stimulated IVF failures using fresh embryos at another clinic. Now she has one baby and another on the way using FET and PGS.
In June 2013, this 40 year-old patient presented to my office with a history of 2 years of infertility due to a tubal factor. At her former clinic, she underwent 3 stimulated IVF cycles retrieving 11-16 eggs with 2-3 fresh embryos transferred in each cycle. No pregnancy occurred. They cryopreserved one extra embryo, which I asked her to transfer to our facility for a natural cycle FET and she became pregnant but unfortunately, this pregnancy miscarried because of Turner’s syndrome, a genetically abnormal pregnancy. I suggested another stimulated IVF adding PGS and, importantly, cryopreservation of all of her embryos. Three PGS normal embryos were produced. A single frozen-thawed PGS normal embryo was transferred in her natural menstrual cycle and in April, 2015, she delivered a healthy, genetically normal baby. Currently, she is pregnant again, now at 7 weeks gestation after another natural cycle FET of a single PGS normal embryo. So, this patient who had first failed 3 IVF treatments elsewhere with fresh embryo transfer, now has one baby and another on the way after stimulated IVF with FET and PGS using a single embryo for each transfer.
Besides increasing implantation and the chances for pregnancy, there are many other benefits of utilizing FET and PGS. Multiple pregnancy is reduced to 1% as only one embryo is needed for transfer. And the spontaneous abortion rate is greatly reduced too as only genetically normal embryos are transferred. This translates into fewer treatments in order to achieve pregnancy and makes IVF cost effective.
In summary, for stimulated IVF, use PGS and FET to optimize your IVF success! Best wishes to all! Michael DiMattina, M.D.
Shapiro BS et al, Clinical rationale for cryopreservation of entire embryo cohorts in lieu of fresh transfer. Fertil Steril. 2014:102:3-9
Gomaa H et al, Elective single embryo transfer, Is frozen better than fresh? JBRA Assist. Reprod. 2016; 20(1):3-7
Dahdouh et al. Comprehensive chromosome screening improves embryo selection: a meta-analysis. Fertil Steril. Sept, 2015