The key events in embryonic development should happen at specific time points. Some embryos can develop too fast or too slow, sometimes abnormal division of the cells occurs and abnormalities can form. Time lapse imaging helps in choosing the embryo with the highest implantation potential.
Embryologists will grade embryos on the number of cells, their shape, level of fragmentation, thickness of the outer shell etc.
Without embryo monitoring equipment embryologists may assess an aneuploid embryo to be normal and decide that it is suitable for transfer. But, of course, it may not be normal. If it is abnormal, it may not implant or may lead to a miscarriage. With embryo monitoring, an embryologist has lots of information on how the embryo divides, what it looks like whilst dividing etc. This information can be used to assess whether a normal looking embryo is indeed ‘normal’.
Time-lapse embryo monitoring can also sometimes determine early on which embryos are most likely to make it to the blastocyst stage. This may mean that we can transfer embryos earlier in the knowledge that the best ones have been chosen.