Posts Tagged ‘in vitro fertilization’

 

Craig R. Sweet, M.D.
Reproductive Endocrinologist

 

 

Corey Burke, B.S., C.L.S.
Laboratory Supervisor

 

Introduction

Asking what determines the success rates in embryo donation is an excellent question. The answer, as one might expect, is neither simple nor completely understood.

Embryologists and physicians try to choose the fewest number of healthy embryos for fresh transfers to increase success rates while minimizing multiple pregnancy rates. It is indeed a delicate balance. For example, it is well understood that in Europe, physicians transfer fewer embryos but patients also suffer significantly lower success rates than in North America. (Boostanfar R, et al. Fertil Steril 2012)

What variables do we examine to estimate probable success?

Since donated embryos are cryopreserved, the variables become even more complex compared to fresh embryos. In combining a great deal of published data and over 20 years of IVF and embryo transfer experience, we came up with what we feel are the variables which seem to influence success rates:

Very Important!	Preferred	Less Optimal
Did the fresh cycle in which the embryos were frozen result in a pregnancy & delivery?	Successful pregnancy and delivery	Fresh transfer resulted in miscarriage or no pregnancy
Number of embryos available in a given donated set	Four or more	Three or fewer
Past implantation rates of both fresh and frozen embryo transfers	High implantation rates	Low implantation rates
Quality of the embryos frozen (link)	High quality (Blastocyst)	Medium quality
Age of the women when the eggs were provided to create embryos	Less than 35 years old	35 years of age or older
Overall health of the embryo recipient (link)	Healthy	With treated or untreated medical issues
Important	Preferred	Less Optimal
Stage of growth when the embryos were frozen (link)	Day 5, blastocyst stage	Day 3, 8-cell stage
Technique used to freeze/thaw or vitrify/warm the embryos (link)	Vitrification	Slow freeze
Overall frozen embryo transfer pregnancy rates for facility freezing the embryos	30% or more	Less than 30%
Overall frozen embryo transfer pregnancy rates for facility thawing the embryos (EDI)	High at 30% or more	Less than 30%
Ejaculated vs. surgically aspirated sperm used for fertilization	Ejaculated sperm	Surgically aspiration sperm
Somewhat Important	Preferred	Less Optimal
Was preimplantation genetic testing of the embryos done?	Yes	No
Age of the male producing the sperm	Less than 40 years old	More than 40 years old
Past successful deliveries with other embryos from donating facility	Yes, with past deliveries	Miscarriage, reduced survival of embryos or failed implantation
Probably Unimportant	Preferred?	Less Optimal?
Cryopreservation duration	Less than 10 years?	More than 10 years?

The above variables influence EDI’s decision to both accept embryos from other facilities as well as determine how many donated embryos should be thawed/warmed to achieve a successful delivery.

The importance of the embryo recipient’s health should not be underestimated

In a previous blog, we described how important it was for our embryo recipients to be healthy. (link) Inadequately treated health problems, harmful medications, recreational drug use as well as smoking and weight concerns all play a potential role affecting success rates. It is clear that success depends on both the quality of the donated embryos and the overall health of the recipient.

Are all donating IVF facilities the same?

We understand that not all IVF facilities have the same success rates. Some facilities will have provided EDI donated embryos with consistently high implantation rates while others may provide embryos of consistently lessor quality. EDI examines a facility’s past fresh and frozen embryo transfer pregnancy rates as well as its past history of providing EDI with donated embryos. It does, however, take a fair amount of time to seemingly identify a trend but we endeavor to examine all the variables we can. Our contact management database system was recently upgraded to track these variables more consistently.

Do your embryos make the grade?

Understanding that all of the above variables are quite complex, we endeavored to find a simple way to convert the data into something patients could more easily understand. Since nearly all patients understand the basic A, B & C grades we used to receive in school, we modeled our grading of the embryos around these letter grades.

We created a mathematical model to assess a number of the above variables, converting the final analysis to A+, A, A-, B+, B and B- letter grades. Interestingly, we found the model really did help to predict delivery rates and continue to use it to this day to grade individual embryos as well as entire sets of donated embryos.

What information do we gain on the day of thaw and embryo transfer?

Most frequently, the embryos are thawed just hours before transfer. At times, we may thaw them days prior if, for example, they were frozen early in their development and we want to grow them further before deciding how many to transfer. Therefore, the following last set of variables will also influence success rates:

Important	Preferred	Less Optimal
Survival rates of thawed embryos	100%	Less than 100%
Overall appearance of the thawed embryos	Healthy, expanding and growing	Evidence of cellular damage

If 100% of the embryos, perhaps three out of three, survive the thaw and look healthy, we feel this is a good sign. If only 50% survive, for example perhaps only two of four, then we are concerned that the overall implantation rates will be reduced and that we might need to find more embryos to transfer just to get to the “finish line” of pregnancy and delivery. Ultimately, we want at least two high-quality embryos or up to four less certain quality embryos placed on the day of transfer.

 What are the national success frozen embryo transfer delivery rates?

In 2009, the CDC reported that there were 26,069 frozen embryo transfers performed in the U.S. with an average delivery rate of 31% per embryo transfer procedure. In addition, there were 6,074 frozen embryo transfers using embryos created from donated eggs (i.e., younger women) with slightly higher delivery rates of 34%. Please recall that donated embryos generally come from the very same types of patients listed in these success rates.

 

What are EDI’s success rates?

We do our best to screen the embryos, carefully trying to choose the embryos most likely to implant. We estimate delivery rates with donated embryos to range from 27 – 42%, depending on the many variables listed in this blog, with a multiple pregnancy rates of 20-25%. We wish the success rates were higher, but please understand that frozen/thawed embryos implant and grow less frequently than fresh embryos and these percentages are entirely consistent with the frozen embryo transfer success rates described in 2009, which ranged from 31-34%.

Even with the slightly lower delivery rates compared to fresh embryo transfers, embryo donation remains one of the best and most cost-effective options for patients who cannot otherwise afford egg donation or qualify for adoption. Embryo donation still allows a woman to experience pregnancy and delivery while bonding, nurturing and protecting the ongoing gestation.

Summary

There are many variables that go into determining the potential success rates for a given set of donated embryos. First, we attempt to examine these variables carefully in deciding if EDI will accept the donated embryos. Second, we use this same information to determine how many embryos we should thaw/warm and eventually transfer. The process remains a bit of an ART (pun intended) since the complete understanding of how all of these variables influence each other and the ultimate success rates are yet to be fully known.

References

“Annual ART Success Rates.” Centers for Disease Control and Prevention. Division of Reproductive Health, 19 Apr. 2012. Web. 24 Apr. 2012. <http://www.cdc.gov/art/ARTReports.htm>.

Boostanfar R, Mannaerts B, Pang S, Fernandez-Sanchez M, Witjes H, Devroey P; Engage Investigators. A comparison of live birth rates and cumulative ongoing pregnancy rates between Europe and North America after ovarian stimulation with corifollitropin alfa or recombinant follicle-stimulating hormone. Fertil Steril.  2012 Mar 27.