So the first and hopefully last frozen embryo transfer (FET) is planned for next week. I'm really hoping that I get a BFP so crossing everything starting right now! Feel free to back up your truck load of baby dust into my baby yard too!
When it comes to the success rates of our beloved totcicles (i.e., frozen embryos), there's a lot of research and statistics out there. My current pregnancy on home soil is a result of 5-year-old totcicles. Approaching the FET, I had the typical questions. I have not asked Dr. S these questions because given my previous FET experience, I feel good about the upcoming transfer. But here were my typical questions about FETs.
1. How long can embryos be frozen and still be viable? Embryos frozen as long as twelve years have resulted in successful pregnancy. Again, mine was 5 years. With freezing and thawing protocols continuing to improve, embryos frozen more recently may have better outcomes.
2. What is the thaw rate of totcicles? This depends on the freezing and thawing protocols, and the quality of embryos before freezing. Embryos graded higher before freezing tend to be more resilient to freezing and thawing. With my current pregnancy on home soil, I had two final totcicles - although they were good quality, they were the lowest quality of the bunch. They both thawed successfully - I remember giving a big sigh of relief because if none had survive, it would have been a wasted cycle.
Survival rate is also influenced by the stage of development at which your embryos were frozen. Some argue that embryos frozen at earlier stages of development survive freezing better because "they are simpler in structure and still have an intact nuclear membrane" while others argue that blastocysts may survive better because "they have more cells, and therefore can recoup easier from the loss of some of them." The best practice appears to depend on what works best for the clinic and their protocols.
Embryos with an even number of cells also appear to have a higher survival rate (5-10% higher) versus odd number of cells. Finally, embryos created with donor eggs also appear to freeze better than embryos of the same grade created with infertility patient's eggs with a 2-5% higher survival rate.
Focusing on the numbers, typical embryo thaw rates range from 50 to 80% depending on the clinic.
3. Does a success thaw mean all totcicles will be transferred? Some surviving embryos will not be transferred because they will have no surviving cells. Many embryos will be partial survivors with some cell damage. Although the extent of the damage may influence subsequent pregnancy rates, embryos that have been damaged often recover and can still capable of resulting in a live birth. The highest quality embryos are those that survive with 100% of their cells intact. Some have suggested that these embryos are essentially as viable as if they had never been frozen.
4. Is there a lower probability that thawed frozen embryos will produce a pregnancy versus fresh embryos? In general, the success rates of FETs are usually lower than those for fresh embryo transfers. This makes sense because damage may occur during freezing and also because higher-graded embryos are usually transferred fresh.
Summary: In the end, these are "just" percentages. The transfer will either be successful or not. Focus on the positive and plan for the negative but believe in the dream.
Thank you for letting me share this part of my world with you!
When it comes to the success rates of our beloved totcicles (i.e., frozen embryos), there's a lot of research and statistics out there. My current pregnancy on home soil is a result of 5-year-old totcicles. Approaching the FET, I had the typical questions. I have not asked Dr. S these questions because given my previous FET experience, I feel good about the upcoming transfer. But here were my typical questions about FETs.
1. How long can embryos be frozen and still be viable? Embryos frozen as long as twelve years have resulted in successful pregnancy. Again, mine was 5 years. With freezing and thawing protocols continuing to improve, embryos frozen more recently may have better outcomes.
2. What is the thaw rate of totcicles? This depends on the freezing and thawing protocols, and the quality of embryos before freezing. Embryos graded higher before freezing tend to be more resilient to freezing and thawing. With my current pregnancy on home soil, I had two final totcicles - although they were good quality, they were the lowest quality of the bunch. They both thawed successfully - I remember giving a big sigh of relief because if none had survive, it would have been a wasted cycle.
Survival rate is also influenced by the stage of development at which your embryos were frozen. Some argue that embryos frozen at earlier stages of development survive freezing better because "they are simpler in structure and still have an intact nuclear membrane" while others argue that blastocysts may survive better because "they have more cells, and therefore can recoup easier from the loss of some of them." The best practice appears to depend on what works best for the clinic and their protocols.
Embryos with an even number of cells also appear to have a higher survival rate (5-10% higher) versus odd number of cells. Finally, embryos created with donor eggs also appear to freeze better than embryos of the same grade created with infertility patient's eggs with a 2-5% higher survival rate.
Focusing on the numbers, typical embryo thaw rates range from 50 to 80% depending on the clinic.
3. Does a success thaw mean all totcicles will be transferred? Some surviving embryos will not be transferred because they will have no surviving cells. Many embryos will be partial survivors with some cell damage. Although the extent of the damage may influence subsequent pregnancy rates, embryos that have been damaged often recover and can still capable of resulting in a live birth. The highest quality embryos are those that survive with 100% of their cells intact. Some have suggested that these embryos are essentially as viable as if they had never been frozen.
4. Is there a lower probability that thawed frozen embryos will produce a pregnancy versus fresh embryos? In general, the success rates of FETs are usually lower than those for fresh embryo transfers. This makes sense because damage may occur during freezing and also because higher-graded embryos are usually transferred fresh.
Summary: In the end, these are "just" percentages. The transfer will either be successful or not. Focus on the positive and plan for the negative but believe in the dream.
Thank you for letting me share this part of my world with you!
Thanks for this info. We are still agonizing over whether to do fresh transfers to two surrogates at once, or use one surrogate and hope for the best, with FET as a back up. A lot will depend on our harvest and fertilization rate, so we will have to make the final decision next week. Good luck with your totcicles!
ReplyDeleteThanks for the well wishes! Good luck with your decision - it's a pretty tough decision for sure. In the end, both options give you the opportunity to become preggo so I'm crossing fingers for you whatever you decide!
DeleteFingers crossed we get to meet in person- say 9 months from now.
ReplyDeleteThanks for the support!
DeleteVery interesting numbers! Good luck with your FET we will have everything crossed for you! We used a donor for eggs, had a fresh cycle, 4 embies trans, low beta, 1 pregnancy which lasted 10 weeks. We then thawed 4 embies, grew to blostocyst with ALH, transferred all 4 to new surro mum, high beta around 400 and 2 survived resulting in our current pregnancy with our twins due this Christmas eve!
ReplyDeleteCongratulations on the twins! I hope that happens to me!
DeleteGood luck with the embryo transfer next week:) Wishing you all the best!!
ReplyDeleteThanks! The last two weeks of October will be thankfully super-busy with work so the 2ww will most likely go by quickly... I hope! LOL!
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