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Pregnancies achieved after transferring frozen morula/compact stage embryos
Objective:
To report two cases of frozen embryo transfers in which embryos were frozen at the morula/compact stage and pregnancies were achieved after transfer.
Design:
Case report.
Setting:
Private assisted reproductive program.
Patient(S):
Two women had transfer of embryos that were frozen at the morula/compact stage.
Intervention(S):
Human morula/compact embryos were cryopreserved and transferred after subsequent thaw.
Main Outcome Measure(S):
Embryo survival after thawing and subsequent pregnancy outcome.
Result(S):
Three and five compact embryos were frozen on day 4 for two patients, respectively. In the first case, all three embryos survived after thawing, and all were transferred. In the second patient, three of five embryos survived after thawing, and those three surviving embryos were transferred. Pregnancies were achieved in both patients. The first woman became pregnant with twins and delivered two girls weighing 2,270 g and 2,071 g, respectively. The second patient became pregnant with a singleton and delivered a boy weighing 2,837 g.
Conclusion(S):
Human embryos can be frozen and thawed in the morula/compact stage and achieve normal pregnancy. Advantages of embryo freezing/thawing at the morula/compact stage include the following: [1] compared with earlier embryonic stage freezing, morula/compact-stage embryos provide better embryo selection and [2] it is easier and safer to perform assisted hatching on compact-stage embryos when compared with those from other preimplantation stages.