Proportion of Cytotoxic Peripheral Blood Natural Killer Cells and T-Cell Large Granular Lymphocytes in Recurrent Miscarriage and Repeated Implantation Failure: Case-Control Study and Meta-analysis

We aimed to compare the proportion of peripheral blood natural killer (NK) cells (CD3–CD56+) and T-cell large granular lymphocytes (CD8+CD57+) during preconception in a homogenous group of women with unexplained well-defined recurrent miscarriage (RM) and repeated implantation failure (RIF) vs healthy controls in relation to pregnancy outcomes. This case–control study followed by a literature review and meta-analysis was conducted in three university hospitals. Patients and controls were consecutively recruited from December 2015 to October 2017. In total, 115 women were included in the study: 54 with RM, 41 with RIF and 20 healthy controls with ≥ 2 term births. Percentages of CD3–CD56+ and CD8+CD57+ cells and sub-populations of CD3–CD56+ cells did not differ between cases and controls. The results for women with subsequent miscarriage did not differ from those with live births. The meta-analysis of the literature showed higher NK-cell proportions in RM [mean difference 3.47 (95% CI 2.94–4.00); p