We speak of refractory endometrium when, in spite of a correct endometrial preparation, this endometrium does not acquire the size and thickness necessary to have a good guarantee of pregnancy.
In these cases the implantation rate, the clinical gestation rate and the live birth rate are reduced. An increase in the rate of miscarriage has not been observed.
When faced with a woman with a refractory endometrium, we must take two approaches. First, perform a hysteroscopy to try to find the cause of the endometrium not growing sufficiently and correct it.
On the other hand, changing the endometrial preparation strategy can also be of great help. Not all endometria respond equally to all estrogens. Some endometrium responds better to a different route of administration (for example, changing the patches for pills), or to a higher dose of estrogens (increasing the dose always within the safe doses), or to the estrogens specific to the woman's cycle (using the natural ovarian cycle instead of giving estrogens externally), etc.