BACKGROUND AND PURPOSE:

• There is some evidence that cryopreserved-thawed embryo transfers lead to higher live birth rates than fresh embryo transfers in IVF cycles
• Data is limited for donor embryo transfers
• Insogna et al. (JAMA, 2021) examined whether a fresh donor embryo transfer is more likely to result in a live birth vs cryopreserved-thawed embryo transfer

METHODS:

• Retrospective cohort study
• Data sources
  • The Society for Assisted Reproductive Technology (SART)
• Participants
  • IVF recipients undergoing fresh donor oocyte cycles in the US between January 2014 and December 2017
• Exposures (freshly retrieved donor oocytes)
  • Fresh embryo transfer
  • Cryopreserved-thawed embryo transfer
• Study design
  • Analyses were adjusted for potential confounding: Donor age | Day of embryo transfer | Use of a gestational carrier | Assisted hatching
• Primary outcome
  • Live birth rate
• Secondary outcome
  • Clinical pregnancy rate
  • Miscarriage rate

RESULTS:

• 33,863 embryo recipients underwent assisted reproduction with freshly retrieved donor oocytes
• The following were similar between exposure groups
  • Median (IQR) age: 42.0 (37.0 to 44.0) years vs 42.0 (36.0 to 45.0) years
  • Gravidity: 1 (0 to 2) vs 1 (0 to 3)
  • Parity: 0 (0 to 1) vs 1 (0 to 1)
  • BMI: 24.5 (21.9 to 28.7) vs 24.4 (21.6 to 28.7)
• 51,942 embryo transfer cycles
  • Fresh embryo transfer cycles: 29.5%
  • Cryopreserved-thawed embryo transfer cycles: 70.5%
• There was no significant difference in the mean number of embryos transferred between the groups
  • Fresh: 92.4% blastocysts transferred
  • Cryopreserved-thawed: 96.5% blastocysts transferred
• Live birth rate was higher following fresh embryo transfer vs cryopreserved-thawed embryo transfer
  • Fresh: 56.6%
  • Cryopreserved-thawed: 44.0%
  • Absolute difference 12.6% (95% CI, 11.7% to 13.5%)
  • Adjusted relative risk (aRR) 1.42 (95% CI, 1.39 to 1.46)
• Clinical pregnancy rates were higher following fresh embryo transfer
  • Fresh: 66.7%
  • Cryopreserved-thawed: 54.2%
  • Absolute difference 12.5% (95% CI, 11.6% to 13.4%)
  • aRR 1.34 (95% CI, 1.31 to 1.37)
• Miscarriage rates were similar between the two groups
  • Fresh: 9.3%
  • Cryopreserved-thawed: 9.4%
  • Absolute difference 0.2% (95% CI, −0.4% to 0.7%)
  • aRR 0.98 (95% CI, 0.91 to 1.07)
• PGT-A did not impact outcomes

CONCLUSION:

• Compared to cryopreserved-thawed embryo transfer, fresh embryo transfer led to higher birth rates and clinical pregnancy rates among women undergoing assisted reproduction using freshly retrieved donor oocytes
• Limitations of this study include missing data from the SART database and the potential for selection and confounding bias
• The authors note that while reporting on obstetrical outcomes was beyond the scope of this study

Use of donor oocytes independently increases the risk of preeclampsia, and whether this is in part due to the type of uterine preparation needs to be elucidated in future studies

Learn More – Primary Sources:

Association of Fresh Embryo Transfers Compared With Cryopreserved-Thawed Embryo Transfers With Live Birth Rate Among Women Undergoing Assisted Reproduction Using Freshly Retrieved Donor Oocytes

Related ObG Topics:

Frozen or Fresh Embryos for IVF Transfer?

RCT Results: Fresh vs Frozen Strategy for Embryo Transfer?

Embolism Following IVF: Does Fresh or Frozen-Thawed Transfer Matter?

ACOG Addresses Preimplantation Genetic Testing