A comparison of day 5 and day 6 blastocyst transfers.
OBJECTIVE
To compare implantation and pregnancy rates according to the day of embryo transfer (day 5 or 6 after oocyte retrieval) when transfer was postponed until expanded blastocysts developed.


METHODS
Retrospective clinical study.


METHODS
Private ART center.


METHODS
One-hundred and eighty-three women undergoing blastocyst-stage embryo transfer following in vitro fertilization.


METHODS
Bipronucleate oocytes were grown for up to 144 hours and subsequently transferred only when at least one embryo attained the expanded blastocyst stage.


METHODS
Implantation and pregnancy rates.


RESULTS
Blastocysts transferred on day 5 implanted at nearly twice the rate of blastocysts transferred on day 6 (36.3% vs. 19.0%). Pregnancy rates were also almost twice as high among the day 5 transfer patients (59.3% vs. 32.3%). In addition, more blastocysts developed (3.6 vs. 2.4), and more were transferred (2.7 vs. 2.3) to the day 5 transfer patients, although the proportion of expanded blastocysts among the blastocysts that were transferred was the same for the two groups (91.7% vs. 93.6%).


CONCLUSIONS
Embryos that develop to the expanded blastocyst stage and are transferred on day 5 after retrieval are approximately twice as likely to implant compared to those for which expansion and transfer are delayed until day 6.
Shapiro
B S
BS
Fertility Center of Las Vegas, Las Vegas, Nevada 89117, USA.
Richter
K S
KS
Harris
D C
DC
Daneshmand
S T
ST
D000328:Adult; D001755:Blastocyst; D010064:Embryo Implantation; D004624:Embryo Transfer; D005260:Female; D005307:Fertilization in Vitro; D006801:Humans; D011247:Pregnancy; D018873:Pregnancy Rate; D012189:Retrospective Studies; D013997:Time Factors