Is it successful the frozen embryo transfer?
Since the first live births following cryopreserved human embryo transfer were announced in 1984 and 1985, the use of frozen embryo replacement has increased worldwide. Since that time, the original protocols have been modified and developed such that cryopreservation may lead to successful survival of up to 80% of the embryos frozen.
The last decade has witnessed a dramatic improvement in frozen embryo transfer and successful IVF rates. The size of the improvement has now lead to equal pregnancy rates for frozen/thawed and fresh embryo transfer as a new report on assisted reproductive technology in Australia and New Zealand has announced. More specifically, birth rates have been increased at about 25% in IVF cycles using cryopreserved embryos over the last five years, compared to fresh embryo transfer where birth rates remained steady (23%). The development of rapid freezing techniques, known as vitrification, versus the ‘’older’’ slow freezing technique has greatly contributed to that improved outcome.
Unsurprisingly, the report also found that in the five years leading up to 2013 the percentage of frozen embryos used in IVF cycles has increased from 39% to 45%. This is probably due to the fact cryopreservation increases the total reproductive potential of assisted reproductive technology, expanding the treatment options for the patients.
As previously mentioned, results obtained with cryopreserved embryos are as good as those obtained when transferring fresh embryos. However there are studies suggesting a higher implantation rate with frozen embryo transfer. This could possibly be explained by the fact that pregnancies following a frozen embryo transfer are more similar to natural conception pregnancies than fresh embryo transfer cycles.