Contrasting patterns in in vitro fertilization pregnancy rates among fresh autologous, fresh oocyte donor, and cryopreserved cycles with the use of day 5 or day 6 blastocysts may reflect differences in embryo-endometrium synchrony

Fertil Steril. 2008 Jan;89(1):20-6. doi: 10.1016/j.fertnstert.2006.08.092. Epub 2007 Jan 16.

Abstract

Objective: To compare the effect of day 5 and day 6 blastocyst transfers on patterns of implantation rates and pregnancy rates (PRs) among fresh autologous, oocyte donor, and frozen ET (FET) cycles.

Design: Retrospective study.

Setting: Private fertility center.

Patient(s): The study included 377 fresh autologous cycles, 106 autologous FET cycles, and 56 fresh oocyte donor cycles.

Intervention(s): None.

Main outcome measure(s): Implantation rates and clinical PRs.

Result(s): The clinical PR for day 5 blastocyst transfers was higher than for day 6 blastocyst transfers in fresh autologous cycles (PRs, 51.0% and 33.3%, respectively). However, there was no significant difference between transfers of blastocysts cryopreserved on day 5 and day 6 in FET cycles (PRs, 63.6% and 58.9%, respectively). Furthermore, day 6 blastocyst transfers significantly outperformed day 5 transfers in donor cycles (PRs, 63.0% and 86.2%, respectively), a reversal of the pattern seen in the fresh autologous cycles. Day 6 blastocysts were associated with a significantly greater PR in FET cycles than in fresh autologous cycles (58.9% and 33.3%, respectively).

Conclusion(s): The superior PRs with day 5 blastocyst transfers in fresh autologous cycles and with day 6 blastocysts in donor cycles may have resulted from better synchrony with endometrial development. This was further supported by the superior performance of day 6 blastocysts in FET cycles relative to their fresh counterparts. Similar PRs with cryopreserved day 5 and day 6 blastocysts in FET cycles may reflect that, in these cycles, day 5 and day 6 blastocysts had equivalent quality and similar synchrony with the endometrium.

Publication types

  • Comparative Study

MeSH terms

  • Adult
  • Cryopreservation*
  • Embryo Culture Techniques
  • Embryo Implantation*
  • Embryo Transfer*
  • Endometrium / physiopathology*
  • Female
  • Fertilization in Vitro*
  • Humans
  • Infertility, Female / physiopathology
  • Infertility, Female / therapy*
  • Menstrual Cycle
  • Oocyte Donation*
  • Oocyte Retrieval
  • Ovulation Induction
  • Pregnancy
  • Pregnancy Rate
  • Retrospective Studies
  • Time Factors
  • Tissue Preservation / methods*
  • Treatment Outcome