Embryo with Eight Blastomeres or More was Better Than 6-7 Cell Stage for Cleavage-Stage Embryo Biopsy: Cryopreserved Mouse Model

Abstract

Objective      To determine whether the embryo with 8 blastomeres or more was most

proper in cleavage-stage embryo biopsy    

Design          Experimental study

Setting          Assisted Conception Unit, University College Hospital, UK

Subjects       Cryopreserved cleavage-stage mouse embryos

Intervention Ninety-seven cryopreserved mouse embryos were thawed. Sixty-seven of
which contained 8 blastomeres or more (group A), whereas 30 embryos contained less than
8 (group B). All embryos were randomly biopsied by two different techniques, acid Tyrode’s
solution and infrared 1.48 mm laser assisted biopsies. All embryos were evaluated on day 4
and 5 of embryonic development. Blastocyst formation, grade of blastocysts and hatching
were assessed and statistically analysed.
Results No significant difference in the blastocyst formation and percentage of grade 1
blastocysts between group A (97.0%, 75.3%) and group B (93.3%, 64.2%). The hatching
rate of the group A (90.7%, 59/65) was significantly higher than that of the group B (60.7%,
17/28). Among the embryos biopsied with acid Tyrode’s solution, the hatching rate of group
A (93.5%) was still significantly higher than that of group B (50.0%). However, there was no
significant difference in hatching rates between the two groups in laser assisted biopsy
(88.2%, group A versus 75.0%, group B).
Conclusion The embryo with eight blastomeres or more was most preferable for cleavagestage embryo biopsy. Hatching rate was found to be the most sensitive parameter to
evaluate the developmental potential following biopsy. The infrared 1.48 mm laser may be
effective and safe for cleavage-stage embryo biopsy