Embryo grading

Embryo selection plays an important part in maintaining pregnancy rates with elective single embryo transfer (eSET), for treatment with both fresh and frozen embryos. Simple morphological assessment can be used to predict embryos with the highest implantation potential.

Currently there is no standardised protocol for grading embryos, with clinics using different criteria and scoring systems.

Joint professional guidelines for implementing eSET are currently being produced by the British Fertility Society (BFS) and the Association of Clinical Embryologists (ACE). As part of these guidelines, ACE will be recommending an evidence-based scoring system which may then be used nationally.

Used in conjunction with both internal and external quality assurance schemes (which are also currently under development), this system may improve the selection of embryos for both transfer and cryopreservation.

A computer-based embryo scoring model has recently been developed in Sweden.  It was combined with a clinical scoring model, taking into account factors such as a woman’s age and previous IVF attempts, to minimise the twin implantation rate while maintaining high pregnancy rates. This work may be useful to attempts to develop more consistent embryo grading and eSET criteria for the whole of the UK.