CD4+ and CD8+ preimplantation endometrial population in women with unexplained recurrent miscarriage

Recurrent early pregnancy loss (RPL) means the loss of ≥ 3 consecutive first-trimester gestations. Unfortunately, it is not uncommon in obstetrics and affects up to 5% of females [1, 2]. Many obstetricians recommend starting the management after only 2 abortions, especially in those over 30 years old [3, 4]. The main issue in such pregnancy failures is usually a disturbed maternal-embryonic interaction, genetic examinations of the abortuses are usually normal [5–9]. Other factors include chromosomal abnormalities as balanced translocations, endocrinopathies, acquired or hereditary thrombophilias, and uterine cavity abnormalities [2, 10–12]. In more than 50% of cases, no cause is identified, and the management will be empirical [13–15]. Abnormal maternal embryonic interaction includes a rejection of the semi-allogenic embryo during “window of implantation” [16–21]. The pre-implantation leukocyte population, which represent > 20% of endometrial cells, was studied to detect the differences between RPL women and healthy controls, and even to predict the outcome. Endometrial immune cells differ to a large extent throughout the phases of the menstrual cycle [20, 21]. So, timing of endometrial biopsy is crucial to achieve valuable results. Early in the pregnancy, just before the start of a subsequent abortion, would logically be the ideal time. However, it is still vague if variants in endometrial cells populations are the underlying mystery of miscarriage. As early gestation, endometrial biopsies in patients with recurrent abortions are likely to have a negative effect on the baby and are thus avoided