Recurrent implantation failure: when good embryos do not stick

There is no single, universally accepted definition, but recurrent implantation failure is generally discussed when several good-quality embryos have been transferred, often three or more, without achieving pregnancy. It is important to understand that transferring an embryo never guarantees implantation; even in the best conditions, each transfer has a chance, not a certainty. Several unsuccessful transfers therefore do not always mean something is 'broken'; sometimes it is simply the statistics of treatment.

This does not lessen the pain. But it puts the situation in context: the aim of evaluation is not to find a culprit at all costs, but to check carefully whether there is something that can be improved, while accepting that the main factor often remains the chromosomal side of the embryo, linked to age.

A considered evaluation looks at several verifiable things. The womb and its cavity, to rule out polyps, fibroids distorting the cavity, adhesions or a septum, often with hysteroscopy or a specialised ultrasound. The lining and how it is prepared for transfer. Hormones, including the thyroid and prolactin. Lifestyle factors known to matter, such as smoking and weight. And the embryo side itself, where genetic testing sometimes makes sense in certain groups.

These checks make sense because, when they find something, it can be treated and the next transfer done in better conditions. The aim is to remove real, fixable obstacles, not to fill a list of tests for its own sake.

This is the area where patients are most vulnerable, because the wish to do 'something more' is understandable. Many tests and treatments are advertised as solutions for implantation failure — various immune tests, therapies aimed at the 'immune system', endometrial scratching, and others. For most of them the evidence is weak or absent, and some carry risk. International guidelines are cautious precisely because these interventions often add cost and hope without raising the real chance.

This does not mean nothing can be done; it means each step should have a reason. A treatment that addresses a problem that was found is different from a treatment given 'just in case'. An honest team will tell you when a test or treatment is unlikely to help you, even when you would like to try it.

Even after a full evaluation, in a proportion of cases no clear cause is found. This is disappointing, but it does not mean there is no hope. Many couples achieve pregnancy on a later transfer with no dramatic change, simply because each transfer has its own chance and time works in your favour when the embryos are good.

In these cases the strategy is often to continue calmly: well-planned transfers, appropriate support, and realistic expectations. Sometimes it helps to take a short break to recover strength. What does not help is adding interventions without evidence under the pressure of anxiety; a calm, honest plan is worth more.