A Pre-Conceptual Endometrial Test to Predict Pregnancy Outcome in Recurrent Pregnancy Loss

Recurrent pregnancy loss (RPL) and recurrent implantation failure (RIF) are major barriers to wanted pregnancies. Currently, there are few tests that reliably predict pregnancy outcome in these groups. Recent research demonstrated that an aetiological factor in early reproductive failure is impaired endometrial decidualisation due to accelerated senescence and loss of endometrial mesenchymal stem cells. Uterine Natural Killer (uNK) cells maintain homeostasis by clearing senescent decidual cells. I aimed to improve the ability of the uNK cell density test in predicting subsequent pregnancy outcomes, through a combined preconceptual test that includes cell senescence and proliferation markers. Methods This study was performed in a tertiary research 'Implantation Clinic', where the uNK cell density test is performed on mid-luteal endometrial biopsies in women with RPL and RIF. I began my investigation of a predictive test by assessing the predictive ability of the uNK test using the clinic's large retrospective database (N=281). Next, immunohistochemistry was performed on endometrial serial sections of women with RPL using antibodies to CD56 (uNK), Ki67 (cell proliferation), HMGB2 and p16 (cell senescence) via an automated staining process. The images were analysed using Pannoramic Viewer and Image J software with colour de-convolution and thresholding technique. The findings of the exploratory test set (N=20) were used to develop a preconceptual combined test for outcome prediction in a larger study (N=89). Final validation of the combined test 'uNK-glandular p16' was conducted on samples from women with RPL recruited in the setting of a prospective, randomised-controlled trial (RCT). Results Combining the normalised uNK and glandular p16 results improved the prediction of pregnancy outcome (p=0.0163). The predictive ability of the combined test 'uNK-glandular p16 centile' was validated in the prospective RCT setting. Conclusion Glandular-stromal synchrony appears to be an important determinate of pregnancy outcome and may help focus future research or therapy.