Freezing all embryos for later transfer might therefore improve implantation and pregnancy rates and increase the safety of IVF. Presently, the highest success rates in reproductive medicine are seen in the recipients of donor eggs. These are women who have not had ovarian stimulation - their endometrial tissue has not been exposed to high hormone levels, and they are not at risk of OHSS.
However, while the theory of a freeze-all policy seems attractive - and the technique has been commonly employed as a safety measure when OHSS is a threat - no robust systematic studies have indicated whether the cryopreservation of all viable embryos with later frozen embryo transfer (FET) is associated with better outcomes than fresh embryo transfers.
Now, the first meta-analysis on this subject indicates that the chance of a clinical pregnancy is around 30% higher when all embryos are frozen for later transfer than with fresh embryo transfer. The results were presented today at the annual meeting of ESHRE (European Society of Human Reproduction and Embryology) by Professor Miguel Angel Checa from the Hospital Universitari del Mar in Barcelona, Spain.
The study was a systematic review of the entire literature, which provided a pool of 64 relevant studies - with three randomised trials - performed before December 2011. The current review was based on information from 633 IVF/ICSI cycles in which 316 were randomised to fresh embryo transfer and 317 to FET. Results showed - based on a relative risk calculation - that the probability of a clinical pregnancy is significantly higher from freeze-all cycles than in fresh embryo transfers (a relative risk of 1.31, which was statistically significant). The miscarriage rates did not show significantly differences between the two groups.
"The pooled data demonstrates that embryo cryopreservation and subsequent FET may improve the outcome of assisted reproduction treatment," said Professor Checa. The study recorded an ongoing pregnancy rate of 38% in fresh transfer cycles, and 50% in the FET cycles.
Professor Checa also explained why FET in a later non-stimulated cycle might improve IVF results. He noted that the multiple eggs generated by ovarian stimulation will increase release of the hormone estradiol from the ovary, which affects the receptivity of endometrial tissue. In addition, some recent studies have shown that ovarian stimulation causes changes to the endometrial DNA pattern, which are not evident in the normal receptive endometrium.
Professor Checa added that the results of his study were "preliminary", but statistically robust. However, with other groups known to be performing similar studies, he urged patience until their results were known. "We are quite confident with our results," he said. "But in our view we should wait until the end of the year for results from other studies to confirm our data and recommend a change in IVF policy."
He added that, with improvements in the technologies of embryo cryopreservation (through vitrification), the evolution of freeze-thawed embryos in IVF is now comparable to that of fresh embryos. A freeze-all approach may thus extend that success even further - and with a greater degree of safety. "When we freeze all of the embryos, we completely avoid the risk of OHSS," said Professor Checa. "So freezing all the embryos we collect would avoid the biggest complication that exists in assisted reproduction."
From abstract no: O-169 Tuesday 3 July 2012, 15.30 hrs EEST
Fresh embryo transfer versus frozen-thawed embryo transfer in assisted reproduction technique cycles: a systematic review and meta-analysis
Note: When obtaining outside comment, journalists are requested to ensure that their contacts are aware of the embargo on this release.
The 28th Annual Meeting of ESHRE, the world's largest event in reproductive science and medicine, is taking place in Istanbul from 1-4 July 2012
Christine Bauquis | EurekAlert!
Staying in Shape
16.08.2018 | Max-Planck-Institut für molekulare Zellbiologie und Genetik
Chips, light and coding moves the front line in beating bacteria
16.08.2018 | Okinawa Institute of Science and Technology (OIST) Graduate University
Scientists at the University of California, Los Angeles present new research on a curious cosmic phenomenon known as "whistlers" -- very low frequency packets...
Scientists develop first tool to use machine learning methods to compute flow around interactively designable 3D objects. Tool will be presented at this year’s prestigious SIGGRAPH conference.
When engineers or designers want to test the aerodynamic properties of the newly designed shape of a car, airplane, or other object, they would normally model...
Researchers from TU Graz and their industry partners have unveiled a world first: the prototype of a robot-controlled, high-speed combined charging system (CCS) for electric vehicles that enables series charging of cars in various parking positions.
Global demand for electric vehicles is forecast to rise sharply: by 2025, the number of new vehicle registrations is expected to reach 25 million per year....
Proteins must be folded correctly to fulfill their molecular functions in cells. Molecular assistants called chaperones help proteins exploit their inbuilt folding potential and reach the correct three-dimensional structure. Researchers at the Max Planck Institute of Biochemistry (MPIB) have demonstrated that actin, the most abundant protein in higher developed cells, does not have the inbuilt potential to fold and instead requires special assistance to fold into its active state. The chaperone TRiC uses a previously undescribed mechanism to perform actin folding. The study was recently published in the journal Cell.
Actin is the most abundant protein in highly developed cells and has diverse functions in processes like cell stabilization, cell division and muscle...
Scientists have discovered that the electrical resistance of a copper-oxide compound depends on the magnetic field in a very unusual way -- a finding that could help direct the search for materials that can perfectly conduct electricity at room temperatur
What happens when really powerful magnets--capable of producing magnetic fields nearly two million times stronger than Earth's--are applied to materials that...
08.08.2018 | Event News
27.07.2018 | Event News
25.07.2018 | Event News
16.08.2018 | Life Sciences
16.08.2018 | Earth Sciences
16.08.2018 | Life Sciences