Chronic endometritis (CE) can present with symptoms such as pelvic pain, atypical uterine bleeding, dyspareunia, or leucorrhea, or it can be asymptomatic; it has been recently associated with unexplained infertility, implantation failure, and pregnancy loss. One potential treatment targeted at improving pregnancy outcomes in these cases is empiric antibiotic treatment, and previous research has shown an increased live birth rate after the use of antibiotics in CE. There is little evidence, however, surrounding pregnancy outcomes for treated and untreated CE or the resolution of CE without antibiotics, especially in mild cases. This study was designed to compare pregnancy outcomes between patients receiving antibiotic treatment for CE versus those not receiving treatment in a population of patients undergoing frozen embryo transfer (FET) cycles. This was a retrospective cohort study of patients undergoing FET between January 2020 and May 2023 in China. Inclusion criteria were women receiving one day 5 or 6 blastocyst transfer who had been diagnosed with mild CE after hysteroscopy and endometrial biopsy. Exclusion criteria were maternal age greater than 45, untreated uterine adhesions or malformations, adenomyosis, endometrial thickness greater than 7 mm on the day of transfer, autoimmune disease, and antibiotic use within 3 months of endometrial biopsy. The primary outcome for this study was live birth rate, defined as the delivery of at least one live infant after 28 weeks of gestation. Secondary outcomes were clinical pregnancy, ectopic pregnancy, early pregnancy loss, and late miscarriage. Eligible patients included 681 individuals, with 303 receiving empiric antibiotics and 378 controls. The majority of patients receiving antibiotics were treated with doxycycline, with 12 patients receiving levofloxacin and metronidazole due to an allergy or adverse reaction to doxycycline. Propensity score matching was applied to this cohort, leaving 606 patients in the final analysis in a 1:1 ratio of treated versus untreated. There were no significant differences in live birth rate, clinical pregnancy rate, rate of early pregnancy loss, or late miscarriage rate between patients treated with antibiotics and controls. Sensitivity analysis showed similar results. There were, in addition, no significant differences in perinatal outcomes assessed, which included rates of labor induction, preterm birth, multiple births, gestational diabetes, premature rupture of membranes, fetal distress, hypertensive disorders of pregnancy, macrosomia, low birth weight, and cesarean delivery rate. When divided into subgroups by ESPC cutoffs, results were similar. These results indicate that empiric antibiotic treatment for mild CE did not improve pregnancy outcomes. This highlights the need for more evidence and standardization surrounding ESPC cutoffs for diagnosis and treatment of CE, as well as the need for further research to determine at what point antibiotics may provide a benefit for patients. Clinical implications include discontinuing the practice of giving broad-spectrum antibiotics to patients with CE if there is no benefit to them or any improvement in their outcomes. In addition, it highlights the need to explore treatments that are effective for mild CE, as previous studies have shown that mild CE still significantly negatively impacts pregnancy outcomes compared with patients without CE. (Abstracted from Fertil Steril. 2025 Oct;124(4):711-719. doi: 10.1016/j.fertnstert.2025.05.172)
Xu et al. (Wed,) studied this question.