Matched-cohort comparison of single-embryo transfers in fresh and frozen-thawed embryo transfer cycles.
OBJECTIVE
To discern the potential effect of ovarian stimulation on implantation potential by comparing ongoing pregnancy rates from matched blastocysts in fresh and frozen-thawed single-embryo-transfer cycles.


METHODS
Matched cohort study.


METHODS
Private fertility center.


METHODS
Ninety-three matched pairs of single-blastocyst transfer.


METHODS
Fresh and frozen-thawed embryo transfers were matched on embryo parameters and patient age.


METHODS
Ongoing pregnancy at 10 weeks' gestation.


RESULTS
The fresh and frozen-thawed groups did not differ significantly in blastocyst diameter, inner cell mass size, trophectoderm cell count, patient age, use of genetic screening, or presence of supernumerary embryos. The ongoing pregnancy rate was significantly greater in the frozen-thawed group than in the fresh group for transfers of day 6 blastocysts (54.3% vs. 17.1%, respectively), but not for day 5 blastocysts (60.9% vs. 56.5%, respectively). This resulted in the overall ongoing pregnancy rate to be significantly greater in the frozen-thawed group than in the fresh group (55.9% vs. 26.9%, respectively).


CONCLUSIONS
Autologous day 6 blastocysts transferred in frozen-thawed cycles have significantly greater chance of viable implantation than morphologically equivalent embryos transferred in fresh cycles. This advantage appears to result from impaired implantation of day 6 blastocysts in fresh transfers after ovarian stimulation, suggesting that embryo-endometrium asynchrony is a major cause of impaired endometrial receptivity after ovarian stimulation.
Fertility Center of Las Vegas, Las Vegas, Nevada 89117, USA. bsshapiro@aol.com
Bruce S
BS
Shapiro
Said T
ST
Daneshmand
Humberto
H
Restrepo
Forest C
FC
Garner
Martha
M
Aguirre
Cynthia
C
Hudson
D000328:Adult; D015331:Cohort Studies; D015925:Cryopreservation / Q000706:statistics & numerical data*; D005260:Female; D059247:Fertility Preservation / Q000706:statistics & numerical data*; D006801:Humans; D007247:Infertility, Female / Q000453:epidemiology* / Q000628:therapy*; D008875:Middle Aged; D009505:Nevada / Q000453:epidemiology; D010062:Ovulation Induction / Q000706:statistics & numerical data; D011247:Pregnancy; D011256:Pregnancy Outcome / Q000453:epidemiology*; D015995:Prevalence; D056826:Single Embryo Transfer / Q000706:statistics & numerical data*; D016896:Treatment Outcome