Recurrent Implantation failure (RIF) is the failure of the embryo to implant onto the side of the uterus wall following IVF treatment. Regularly, this happens at 6-7 days after conception and involves the embedding of the growing embryo into the mothers uterus and a connection being formed. A successful implantation can be determined by using an ultrasound to view the sac which the baby grows in, inside the uterus.

However, the exact definition of RIF is debated. Recently the most commonly accepted definition is when a women under 40 has gone through 3 unsuccessful cycles of IVF, when in each cycle 4 good quality eggs have been transferred .

Repeated implantation failure should not be confused with recurrent IVF failure. Recurrent IVF failure is a much more broad term and includes all repeated failures to get pregnant from IVF. Repeated implantation failure specifically refers to those failures due to unsuccessful implanting to the uterus wall.

An unsuccessful implantation can be down to either problems with the mother or with the embryo. It is essential that the mother and embryo are able to communicate with each other during all stages of pregnancy, and an absence of this communication can lead to an unsuccessful implantation and a further unsuccessful pregnancy