Of 969 non-consecutive endometrial biopsies performed for investigation of recurrent reproductive failure, 20 cases (2.1%) showed the striking presence of retarded or asynchronous endometrial glands in otherwise unremarkable mid or late secretory endometrium. These glands were characterised by tall columnar cells with crowded nuclei showing increased reactivity for the proliferative marker MIB-1, occasional mitoses, greatly reduced or absent secretion, and persistent expression of oestrogen receptors and usually progesterone receptors and their isoforms typical of late proliferative phase endometrium. The nearby endometrial stromal cells exhibited no discernibly reduced reactivity for calretinin.
These changes were seen in single glands (even portions of glands), or clusters of glands, adjacent to normal late secretory type endometrial glands and set in pseudodecidualised stroma characteristic of late luteal phase. Some examples also displayed adjacent glands with intermediate features and it is speculated that firstly, this is a relatively common phenomenon in women with recurrent miscarriage or implantation failure and with an unknown potential to affect implantation. Secondly, it is an intrinsic defect of the endometrium and can occur in sequential endometrial biopsies in the same patient. Thirdly, it differs from previously described patterns of so-called luteal phase defect or deficient secretory phase in that it occurs in the demonstrated presence of adequate progesterone effect on the endometrium and is associated with persistence rather than exaggerated down-regulation of receptors.
Nevertheless, supplementary progesterone therapy (vaginal pessaries) for the first trimester appeared to have a beneficial therapeutic effect on reproductive outcome in these patients.