The number of blastomeres in post-thawing embryos affects the rates of pregnancy and delivery in freeze-embryo-transfer cycles.
OBJECTIVE
To observe the differences in pregnancy rates (PRs), delivery rates, and abortion rates associated with frozen-embryo-transfer (FET)-based use of post-thawing embryos with different numbers of blastomeres.


METHODS
959 FET cycles and 361 successful FET cycles performed between January 2007 and December 2007. Compare the PRs and abortion rates in post-thawing embryos with 8 blastomeres (8c), 7c, 6c, 5c, 4c,and 3c.


RESULTS
1. The total PRs of post-thawing 8c, 7c, 6c, 5c, 4c, and 3c embryos were 44.1%, 41.0%, 34.4%, 23.8%, 12.5%, and 0%, respectively (p < 0.05). 2. The abortion rates for the transferred embryos of the 8c, 7c, 6c, 5c, and 4c groups were 17.92%, 19.35%, 27.69%, 24%, 20%, respectively (p < 0.05).


CONCLUSIONS
The number of blastomeres in the post-thawing embryos is an important factor influencing the occurrence of pregnancy in FET procedures; however, the criterion that post-thawing embryos with 50% intact blastomeres will lead to pregnancy may not be valid.
Zhang
ShunJi
S
Institute of Reproductive and Stem Cell Engineering, Central South University, Changsha 410008, China.
Lu
ChangFu
C
Lin
Ge
G
Gong
Fei
F
Lu
GuangXiu
G
D001757:Blastomeres / Q000502:physiology*; D016009:Chi-Square Distribution; D006063:Chorionic Gonadotropin / Q000652:urine; D015925:Cryopreservation / Q000379:methods* / Q000592:standards; D004624:Embryo Transfer / Q000379:methods* / Q000592:standards; D005260:Female; D005307:Fertilization in Vitro / Q000379:methods*; D006801:Humans; D011247:Pregnancy; D012189:Retrospective Studies
D006063:Chorionic Gonadotropin