After insemination by IVF or ICSI, fertilised eggs are the routinely cultured in the laboratory for 3 days before being transferred back into the woman’s uterus.
Before embryo transfer, the embryos are graded by specially trained embryologist in order to select the embryos with the best chance of implanting in the uterus and forming a healthy baby.
The main criteria used to grade embryos on day 3 are:
- The number of cells which the embryo has.
Embryos showing good development will generally have 6 to 8 cells after 3 days of growth. Embryos with fewer cells may still be good, but they are less likely to continue normal development.
- The amount of ‘fragmentation’ that the embryos show.
Fragmentation describes the way that cells of an embryo split off into fragments. A small amount of fragmentation is normal, but excessive fragmentation suggests that the embryo will have a lower chance of continuing normal development.