Many IVF cycles are carried out all of the world and each cycle is different and cannot be compared to one another, this also means then number of eggs collected, injected with sperm and how many of these go on to fertilise are unique to the couple undergoing an IVF cycle.
Today almost 40% of average aged couples undergoing IVF treatment produce multiple good quality embryos. This rate is more than 60% for younger patients because egg reserves and quality tend to decrease with age. Good quality embryos left over from the embryo transfer procedure could be preserved in a cryopreservation chamber dedicated for this purpose inside the embryology laboratory and can be thawed at a later date to transfer.
The procedure of cryopreserving embryos for potential future pregnancies has routinely been carried out around the world for more than 20 years in IVF treatments. There are probably hundreds of thousands of babies born around the world who have been conceived with this method. The prospect of cryopreserving good quality embryos left over from the embryo transfer procedure is medically, financially and spiritually important for many patients. In other words, if freezing can be performed correctly, the method can provide an additional treatment opportunity and chance of conceiving while also significantly reducing total treatment costs. Because this treatment does not require egg development and associated use of high doses of hormone and medication, the process is overall much less troublesome for the patient.
So, is cryopreservation only used to freeze embryos that left over from the treatment? Can any patient get cryopreservation?
Before anything, the key to effective use of embryo freezing/thawing treatments is for the clinic to have a very good record in cryopreservation services. The technological infrastructure of this service might be important but is not enough alone. The first step is embryo quality and selection for cryopreservation, next comes choosing the method for freezing. In this regard, the efficiency of specialists (embryologists) performing the procedure is crucial and requires experience. A high number of IVF clinics offer embryo cryopreservation services but there is tremendous difference in terms of success rates. Reputable IVF clinics offer embryo cryopreservation services to a larger number of patients. On the other hand the chances of successful conception with cryopreserved embryos should be at least the same as fresh embryo treatments. Implantation success after embryo transfer should be higher because the treatment time is focused on the endometrium lining and making the uterus suitable for embryo transfer without focusing on follicular development also.
Due to technical difficulties, until recently embryo cryopreservation was only offered to couples with a specific minimum quantity and quality of embryos. However, today we can offer cryopreservation for a single embryo left over from the treatment should it reach a certain size and quality. In other words, we can now offer this option to a greater number of couples regardless of embryo count, as long as the embryo quality proves to be high. Cryopreservation is not only offered to couples who have embryos left over from treatment, but Cryopreservation is also an effective method in cases where the treatment has to be stopped or postponed. For example, the female may develop Ovarian Hyper-stimulation Syndrome (OHSS), which is when the ovaries over react to the hormone and drug treatments. In such cases, the embryos will be frozen and preserved in their early developmental stage. They can later be thawed and transferred to the patient with high rates of conception, once the clinical outlook returns to normal. As there would be a risk to the patient if embryo transfer was to be carried out after signs of Hyper-stimulation.
Some clinics also adopt the approach of freezing all embryos and postponing the transfer to a future date after all the problems have been resolved and there is a healthier and more natural uterine environment. This is in order to obtain higher conception rates for females who are considered to have thin endometrium lining and embryo holding capacity; they then have to be induced on high doses of medication/drug or for females that have developed a structure (myoma, polyp, etc.) that might prevent the embryo implanting onto the on to the endometrium lining. The number of treatments offering the use of frozen embryos as opposed to fresh ones has been increasing significantly especially in the Far East.
Another application of embryo cryopreservation is for couples that wish to perform genetic diagnosis on their embryos. Regarding embryos developed, couples that have high risk of passing on a genetic disorder but can only produce a limited number of eggs and embryos; They are encouraged to undergo more than one IVF cycle and freeze at day of development to build the number of embryos before carrying out the genetic testing, this also minimises the cost for genetic testing after each cycle if freezing was not a possibility.
What is the success rate of treatment with frozen and thawed embryos?
Frozen embryos can be preserved for several years without losing vitality or causing risk to the embryo, assuming the procedure is applied at a competent clinic and by experienced personnel. Viability of thawing embryo successfully of cryopreserved embryos at such clinics is above 95%. Transferring good quality embryos which have been selected and cryopreserved at these clinics into a natural uterine environment returns 8-10% higher chances of conception compared to fresh embryo transfer.