Markers of endometrial function in women with unexplained recurrent pregnancy loss: a comparison between morphologically normal and retarded endometrium.

Background: Endometrial defect, usually described as luteal phase defect (LPD), is associated with recurrent miscarriage. Recurrent miscarriage has also been associated with the abnormal expression of various molecules by endometrial cells. The aim of this study was to determine if any of these molecules or cells could be used to distinguish LPD from in-phase endometrium.

Methods: Immunocytochemistry was used to compare endometrial expression of CD45+, CD56+, CD3+ and CD4+ cells, leukaemia inhibitory factor, interleukin-6 and estrogen and progesterone receptors in precisely timed endometrial biopsies obtained between days LH+6 and LH+11 from recurrent miscarriage women with in-phase and retarded endometrium.

Results: In all samples there was a positive correlation between the number of CD45+ cells and LH day and a negative correlation between progesterone receptor and LIF expression and LH day. A significantly lower number (P<0.05) of CD56+ cells in peri-implantation endometrium and a decreased mid-cycle estrogen level (P<0.05) was seen in women with LPD compared to in-phase endometrium when single analysis was carried out. However, these differences were not significant after application of the Bonferroni correction for multiple analysis.

Conclusions: The results are in line with previous associations observed between estrogen levels and LPD and suggest that the number of CD56+ cells is different in LPD and in-phase endometrium, although this could be due to delayed endometrial development in women with LPD. Interpretation must be cautious because these differences could have arisen by chance.