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.
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.


METHODS
Retrospective study.


METHODS
Private fertility center.


METHODS
The study included 377 fresh autologous cycles, 106 autologous FET cycles, and 56 fresh oocyte donor cycles.


METHODS
None.


METHODS
Implantation rates and clinical PRs.


RESULTS
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).


CONCLUSIONS
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.
Shapiro
Bruce S
BS
Fertility Center of Las Vegas, Las Vegas, Nevada 89117, USA. bsshapiro@aol.com
Daneshmand
Said T
ST
Garner
Forest C
FC
Aguirre
Martha
M
Ross
Richard
R
D000328:Adult; D015925:Cryopreservation; D046149:Embryo Culture Techniques; D010064:Embryo Implantation; D004624:Embryo Transfer; D004717:Endometrium / Q000503:physiopathology*; D005260:Female; D005307:Fertilization in Vitro; D006801:Humans; D007247:Infertility, Female / Q000503:physiopathology / Q000628:therapy*; D008597:Menstrual Cycle; D018587:Oocyte Donation; D054315:Oocyte Retrieval; D010062:Ovulation Induction; D011247:Pregnancy; D018873:Pregnancy Rate; D012189:Retrospective Studies; D013997:Time Factors; D014021:Tissue Preservation / Q000379:methods*; D016896:Treatment Outcome