Embryo fragmentation occurs when a part of the embryo's cells have broken off and are now separate from the portion of the cell containing the nucleus. These fragments are no longer useful to the embryo.
Fragmentation is quite common in human embryos. However, if more than 25% of the embryo is fragmented, it is less likely to successfully implant in the uterine wall and result in a successful pregnancy.
Embryo fragmentation is also called blebbing.
FertilitySmarts explains Embryo Fragmentation
When an embryo is dividing or cleaving, it sometimes does so unevenly causing portions of the cell to become separated from the nucleus. These fragments serve no function to the embryo. The more fragments an embryo has, the less likely it will result in a successful pregnancy.
What causes fragmentation?
Fragmentation can occur in either naturally conceived embryos or those produced during in vitro fertilization (IVF). The cause of fragmentation is unknown, but its presence in cleavage stage embryos is very common, although in varying degrees.
Fragmentation & Embryo Grading
Because of its potential impact on the success of implantation, fragmentation is an important consideration when grading a cleavage stage embryo.
Grading a cleavage stage embryo involves evaluating a set of characteristics to determine which embryos have the best chance of producing a successful pregnancy. For example, a lab might have a grading system from 1 to 4, where 1 is the best quality and 4 is the poorest quality.
Even cells, no fragmentation
Even cells, slight fragmentation
Uneven cells, moderate fragmentation
Unrecognizable cells, severe fragmentation
The embryo or embryos that are predicted to have the best chances of pregnancy are typically selected for transfer.
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