JBRA Assisted Reproduction 2025;29(Suppl.2 SBRA 2025):209
Poster Presentation
29^th Annual Congress of the SBRA. São Paulo/SP - Brazil, 2025
doi: 10.5935/1518-0557.20263874

P-197. Reproductive Outcomes after Treatment for Chronic Endometritis and Increased Uterine Natural Killer Cells in Women Undergoing In Vitro Fertilization and Frozen Embryo Transfer

Layza Merizio Borges¹, Lara Pin Venturini¹, Larissa Galvão Barreto Carneiro Mazzini¹, José Augusto Ribeiro Almeida¹, Fernanda Machado Mattos Temer¹, Arielle Rocha Oliveira Nascimento¹, Natália Vasconcellos Gonçalves Miranda¹

¹ Instituto de Medicina Reprodutiva - Vitória - ES - Brasil

Objectives: Chronic endometritis (CE) is a persistent inflammatory condition of the endometrium, often asymptomatic and difficult to suspect, even for experienced reproductive medicine specialists. Hysteroscopy can reveal suggestive findings such as endometrial micropolyps, stromal edema, and focal or diffuse hyperemia, but histological evidence of multiple plasma cells in the endometrial stroma remains the gold standard for diagnosis. Syndecan-1 (CD138) immunohistochemical (IHC) staining is the most widely used method for plasma cell identification, offering greater diagnostic accuracy and reproducibility than hysteroscopy alone. Uterine natural killer (uNK) cells play an important role in early placental development, particularly in trophoblast invasion and spiral artery remodeling. Abnormal activation or levels of uNK cells have been implicated in recurrent miscarriage and recurrent implantation failure, possibly through altered cytokine secretion and angiogenic factor imbalance. This study amed to evaluate whether antibiotic treatment for CE and/or Intralipid infusion for elevated uNK cells could improve reproductive outcomes in women undergoing in vitro fertilization (IVF) with subsequent frozen embryo transfer (FET).
Methods: This retrospective study was conducted in a private fertility clinic from January 2023 to April 2025. A total of 113 infertile women undergoing IVF and hysteroscopy with endometrial biopsy prior to embryo transfer were included. Exclusion criteria were submucosal fibroids, uterine malformations, intrauterine masses, endometrial polyps, adenomyosis, stage III/IV endometriosis, and severe male factor infertility. Hysteroscopy was performed in the peri-implantation phase (approximately on day 20 of the menstrual cycle). CE diagnosis was established when ≥1 CD138+ plasma cell was identified in a single high-power field. CE-positive patients received doxycycline (200 mg/day for 14 days). Patients with NK cell levels >15% received a 100 mL Lipofundin 20% infusion diluted in 250 mL saline, administered intravenously 2–7 days before embryo transfer. Patients with both conditions received both treatments. The control group received no treatment. Categorical variables were analysed using the chi-squared test and presented as frequencies and percentages (%), while continuous variables were analysed using one-way ANOVA and presented as means and standard deviations (M±SD). Values of p<0.05 are considered statistically significant.
Results: Of the 113 participants, who had a mean age of 37.4±4.67 years (range 25–45), 33 (29.5%) received no treatment, 54 (47.8%) received only antibiotics, 15 (13.4%) received only Intralipid, and 10 (8.9%) received both treatments. A high prevalence of CE (56.7%) was observed in the studied group. There were no significant differences between groups in terms of age (p=0.626), duration of infertility (p=0.810), anti-Müllerian hormone levels (p=0.253), male factor (p=0.598), tubal factor (p=0.151) or ovarian factor (p=0.184). There were also no significant differences in recurrent miscarriage rates (p=0.492), previous implantation failures (p=0.898) or type of infertility (p=0.606). Biochemical pregnancy (positive β-hCG) (p=0.262) and clinical pregnancy (fetal heartbeat) (p=0.661) rates were similar among the groups. Clinical pregnancy rates were 46% in the control group, 46% in the antibiotic group, 60% in the Intralipid group, and 20% in the combined treatment group. The low clinical pregnancy rate in the combined treatment group may be due to the small sample size.
Conclusion: In the present study, treatment with antibiotics or Intralipid (alone or in combination) for chronic endometritis and/or elevated uNK cell levels produced reproductive outcomes similar to those of the control group (no treatment) in women undergoing IVF/ET cycles. These findings reinforce the need for prospective studies with larger sample sizes and controlled designs to clarify the therapeutic impact of these interventions and establish more definitive protocols for patients with endometrial immunological alterations.