Why Do Euploid Embryos Fail to Implant? The Role of CD138 and Chronic Endometritis

The objective of this prospective cohort study was to investigate the relationship between chronic endometritis (CE) and its treatment on pregnancy outcomes in patients undergoing frozen embryo transfers (FETs) from in vitro fertilization (IVF) with preimplantation genetic testing (PGT) who had previously failed ≥ 1 euploid FET. The diagnosis of CE was made using CD138 as a marker. This study occurred at a single, high volume academic based fertility center. 305 patients were included with a history of ≥ 1 failed euploid transfers. 59 patients underwent endometrial biopsies (EMB) prior to subsequent FET (Tested), 246 patients did not undergo EMB prior to subsequent transfer (Untested). Patients in the Tested group had an EMB prior to subsequent FET, whereas the patients in the Untested group did not have an EMB prior to next FET. Patients tested and found positive for CE were treated with antibiotics and underwent test-of-cure (TOC) EMBs prior to next FET to assess for adequate treatment. Patients without CE on EMB proceeded to next FET without antibiotic treatment. Main outcome measures included positive Beta-hCG (βhCG) on cycle day 28, implantation rate (IR), and subsequent ongoing pregnancy/live birth rates (OPR/LBR). Our results showed that 51% of patients (30/59) were diagnosed with CE and treated with antibiotics (Tested, CE treated); negative TOC biopsies were obtained prior to next FET. 49% of patients (29/59) tested negative for CE (Tested, No CE) and were not treated prior to next FET. Tested patients without CE (CE treated and No CE) had significantly higher incidences of positive βhCG, IR and OPR/LBR than patients who were not tested. Those who were biopsied and treated for CE had significantly higher OPR/LBR compared to patients who were biopsied and negative for CE (80% vs. 55%). We conclude that CE is common, with a prevalence of 51% in patients who have failed euploid FETs. Testing for CE may provide a benefit to patients, assuring higher incidences for positive βhCG, implantation, and subsequent ongoing/live births. CE is a treatable condition warranting investigation in patients with poor pregnancy outcomes.