General information about frozen oocytes

 

  • COS with oocyte cryopreservation is a relatively new option for women who do not have a partner and do not wish to use frozen sperm. 
  • Compared with the use of frozen embryos, there is a lot less known frozen oocytes, such as accurate predictions of pregnancy rates and birth defect rates.
  • The American Society of Reproductive Medicine no longer classifies oocyte cryopreservation as experimental1.

Birth defect rate

 

  • A compilation of published studies demonstrated that over 900 oocytes cryopreservation babies do not demonstrate in increased rate of congenital abnormalities, compared to naturally conceived infants2
  • This study included both methods of cryopreservation – vitrification and slow-freeze. 

Pregnancy rates

 

  • Data regarding pregnancy rates from frozen oocytes has been limited, but reassuring. 
  • Most of the published data is in egg-donation cycles and demonstrates no difference in fertilization and pregnancy rates as compared to fresh donor cycles3, 4.   
  • However, most reproductive-aged women with cancer are older than egg donors – the average age for the 295 donors was 26.7 years in the study by Cobo et al3
  • Data about live-birth rate after oocyte cryopreservation is very limited in women age 30-42. 
  • In a series of 15 couples with infertility and 6 egg-donation cycles (average age 31.5 years) undergoing COS with oocyte cryopreservation, Grifo et al. noted no difference in live-birth rates as compared to an age-matched, fresh historical controls5

Some additional considerations with oocyte cryopreservation

 

  • ICSI must be done for fertilization, regardless of sperm parameters.  This is due to the hardening of the zona pellucida.
  • Patients without a partner can opt to freeze some oocytes, and some embryos (using donor sperm for fertilization). 
  • ASRM has guidelines about the essential elements of informed consent of elective oocyte cryopreservation6.  One can argue that a similar outline for counseling be provided to cancer patients who are contemplating oocyte cryopreservation.
  • In the absence of clinic-specific outcomes data about live-birth rates after oocyte cryopreservation, ASRM recommends using these estimates based on published literature:
    • ~2% live-birth rate per oocyte thawed following slow-freeze methods
    • ~4% live-birth rate per oocyte thawed following vitrification
    • The likelihood of success may be significantly lower in women over the age of 35, as most published reports are for younger women.6

References

1. Practice Committee of Assisted Society of Reproductive Medicine. Ovarian tissue and oocyte cryopreservation. Fertil Steril 2008;90:S241-6.

2. Noyes N, Porcu E, Borini A. Over 900 oocyte cryopreservation babies born with no apparent increase in congenital anomalies. Reprod biomed Online 2009;18:769-76.

3. Cobo A, Meseguer M, Remohi J, Pellicer A. Use of cryo-banked oocytes in an ovum donation programme: a prospective, randomized, controlled, clinical trial. Hum Reprod;25:2239-46.

4. Nagy ZP CC, Bernal CP, Shapiro DB, Mitchell-Leef D, Kort HI. Comparison of laboratory and Clinical Outcomes between fresh and Vitrified/Warmed Sibling Oocytes Obtained from 30-39 year old IVF Patients. Fertil Steril 2009;92-S67.

5. Grifo JA, Noyes N. Delivery rate using cryopreserved oocytes is comparable to conventional in vitro fertilization using fresh oocytes: potential fertility preservation for female cancer patients. Fertil Steril 2009.

6. Practice Committee of Assisted Society of Reproductive Medicine Essential elements of informed consent for elective oocyte cryopreservation: a Practice Committee opinion. Fertil Steril 2007;88:1495-6.

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, 2013.