When estimating the chance of pregnancy from frozen embryos, one must consider the:

 

  • Chance of survival of frozen embryos
    • Depends on embryo stage at time of cryopreservation (2PN, cleavage, blast)
    • Center-specific rates
  • Pregnancy rate per embryo transfer cycle
    • Number of embryos transferred
    • Age of women when embryos were created
    • Center-specific rates
  • Risk of miscarriage
    • Related to the age of women when embryos were created
  • Number of embryos frozen – affects the number of possible embryo transfer cycles
  • One important fact is that the chance of live-birth does not vary based on the age of the woman at the time of the embryo transfer.  If a 30 year old woman banks embryos, her chance of pregnancy is essentially the same if she decides to undergo a frozen embryo transfer when she is 31 or 35 or 45!  The chance of pregnancy is linked to her age at the time of banking. 

Can we give a blanket estimate of future pregnancy?

 

  • Lawrenz et al. estimate the chance of live-birth from the transfer of two pronuclear embryos to be approximately 15%1
  • However, this clearly varies based on the woman’s age, stage of the embryos at time of cryopreservation, and center-specific success rates. 

The Society for Reproductive Technology (SART) database  gives an approximation of frozen embryo transfer success rates, based on age

 

  • There are limitations in using these estimates when considering pregnancy rates for cancer patients:
  • SART does not specify the stage of the embryo at the time of cryopreservation (2PN, cleavage, blast)
  • SART does not publish data on embryo survival rate
  • Most patients in the SART database are infertile couples, whereas most cancer patients do not have a known fertility problem at the time of banking
  • Most patients in the SART database underwent a fresh embryo transfer using their ‘best’ embryos.  Cancer patients have frozen all of their embryos; presumably, the ‘best’ embryos remain in the pool that is frozen. 


 Thawed Embryos

<35

35-37

38-40

41-42

>42

Number of transfers

10,757

5,519

4.065

1,305

961

% of transfers with live-births

35.6

30.9

26.1

22.1

13.9

Average # of embryos transferred

2

2

2.1

2.3

2.3

Reference:

1. Lawrenz B, Jauckus J, Kupka M, Strowitzki T, von Wolff M. Efficacy and safety of ovarian stimulation before chemotherapy in 205 cases. Fertil Steril 2010;94:2871-3.

About the Author

Jennifer Mersereau, MD, MSCI, is an reproductive endocrinologist in the University of North Carolina's Department of Obstetrics and Gynecology. As the Director of the Fertility Preservation Program, she has extensive experience guiding patients and physicians through the oncofertility experience.

Page last updated March 14, 2012.