Hana Visnova, MUDr., PhD
Medical Director at IVF CUBE, IVF CUBE
Donor Eggs, Success Rates
As some of you may know, the human egg is one of the largest cells in the body – with a diameter of about 0.1 millimetre, it’s usually visible to the naked eye. Because of its size and of the water quantity inside the cell, preventing ice formation became a major issue. During the early days of fertility treatments, it was believed that because of the slow freeze method which was used at the time, only one in a hundred frozen eggs would result in a pregnancy.In 2007, however, a new method was developed – vitrification, which drastically improved the survival rate of oocytes, as well as the pregnancy rate – five pregnancies can now be achieved from a hundred frozen cells, rather than just one. Sperm freezing, comparatively, is uncomplicated; the method has been known for about sixty years and from the earliest attempts has enjoyed high success rates. Because of the characteristic of human sperm, it is much easier to cryopreserve when compared to egg cells. From the infertility clinics’ perspective, egg banking offers a major advantage – it makes the entire treatment process much simpler to plan, as the need to synchronize cycles between the donor and the recipient simply isn’t a factor. Additionally, the process allows more time for additional testing, if needed. In some countries, such as the United States, clinics are allowed to use donated eggs from affiliated fertility institutions, which significantly expands the available donor pool. If we look at egg banking from the patient’s perspective, advantages can also be found; for instance, about 5% of fresh egg donation cycles are cancelled due to donor-side issues, such as hyperstimulation. Obviously, banked eggs bypass that issue entirely. Additionally, it is much easier to find a donor of a matching phenotype when opting for a banked egg transfer – which cuts down on the waiting time. Another advantage is the complete lack of a down- regulation cycle, avoiding the possible side effects from the medications used in such cycles, making the treatment much more comfortable. Because of the relaxed time constraints, treatments could be scheduled to align with the natural cycle – again, reducing the need for additional medication. This helps patients and clinics schedule treatment to respect job commitments and travel arrangements. The big question, however, remains – does egg banking provide identical or comparable success rates to treatments using fresh egg donations? Dr Visnova’s clinic, IVF Cube, commissioned a study to help determine an answer. They were also interested in whether frozen oocytes resulted in similar numbers of good quality embryos when compared to fresh donor eggs, and whether the implantation and successful live birth rates are comparable. Their analysis compared 266 fresh egg donation cycles to 63 cycles using frozen donor oocytes. The total pregnancy rate for fresh eggs was 68.05%, while that of the frozen oocytes was 42.86%. Of all the egg cells suitable for ICSI fertilisation per cycle, 100% of fresh eggs and 93% of frozen oocytes were suitable. The fertilisation rates per cycle were 84.81% and 72.97% for fresh and frozen oocytes, respectively. Fresh eggs resulted in at least one high quality embryo in 96.24% of all cycles, with frozen ones trailing behind at 61.9%.
Dr Visnova sums the study up as such: the numbers indicate that higher numbers of frozen oocytes are required to ensure the generation of a good embryo at the blastocyst stage. Conversely, on average, almost two surplus high quality embryos are produced each cycle, which can be frozen for future use.When it comes to results, we can see a marked statistical difference between using frozen and fresh donor eggs. On average, IVF Cube required only around 7 fresh eggs to achieve a successful pregnancy, while it needed twice that amount in frozen oocytes for the same result. Because the clinic used about 11 eggs per cycle during the study, some patients did not achieve a successful pregnancy during the first cycle. Dr Visnova’s conclusions are then as such: while fresh donor cycles are time-consuming and require more management from both the patient and the clinic to arrange a workable schedule, fresh oocytes have a higher cumulative success rate and have a higher chance of producing surplus embryos which can then be used in future treatments. In her opinion, the freezing and banking of donor eggs is a waste of biological material; her clinic continues to recommend fresh donation cycles for patients.