Recurrent (or repeated) implantation failure is an imprecisely defined and disputed clinical disorder that is characterised by failure to achieve pregnancy after repeated embryo transfers.

It can be defined as a failed embryo implantation, where beta-hCG is in the negative range, after a number of embryo transfers.

The term ‘implantation failure’ should be reserved for this specific scenario and not be used to describe early biochemical pregnancies that may have a different underlying aetiology.

Although the concept of recurrence clearly implies repeated failed embryo implantation, the precise number of failed transfers to be classified as ‘recurrent implantation failure’ is not well established.