Yuye Li ^1,2 Shuyi Yu ^1,2 Wenjuan Liu ³ Yawen Chen ^1,2 Xiaobing Yang ^1,2 Juanhua Wu ^1,2 Mingjuan Xu ^1,2 Guanying You ^1,2 Ruochun Lian ^1,2 Huang Chunyu ^1,2 Wanru Chen ^1,2 Yong Zeng ^1,2 Fenghua Liu ^3* Lianghui Diao ^1*

• ¹ Shenzhen Zhongshan Obstetrics & Gynecology Hospital, Shenzhen, China
• ² Guangdong Engineering Technology Research Center of Reproductive Immunology for Peri-implantation, shenzhen, China
• ³ Guangdong Province Women and Children Hospital, Guangzhou, Guangdong Province, China

Objective: This study was conducted for determining how many CD138 + cells in the proliferative endometrium have an influence on pregnancy outcomes.Methods：This retrospective cohort study was conducted from January to August in 2018. A total of 664 infertile women without doing CE analysis and without receiving respective antibiotic treatment were studied. Immunostaining was performed for the plasmacyte marker CD138. The amount of CD138+ cells was compared in the proliferative and mid-luteal phases of the same patients without antibiotic therapy.Infertile patients were separated into three groups based on the number of positive lesions (the number of high power fields (HPFs) containing not less than five CD138 + cells): 0 ( n = 474), 1-2 (n = 125) and ≥ 3 positive lesions (n = 104). Then, the pregnancy outcomes of infertile women undergoing in vitro fertilization-embryo transfer (IVF-ET) among three groups were compared.Results：CD138+ cells during proliferation demonstrated a greatly higher level than those during the mid-luteal phase (P <0.0001). Pregnancy outcomes did not differ between 0 and 1-2 positive lesions. However, the ≥ 3 positive lesions group (P =0.006, P =0.029) had significantly lower ongoing pregnancy and live birth rates compared with the 0 positive lesion one. Although 0 and ≥ 3 positive lesions groups showed a trend toward higher rates of clinical pregnancy (P =0.132), these differences failed to reach statistical significance. After the age, body mass index (BMI) and clinical features were adjusted, the ≥ 3 positive lesions group showed significantly lower live birth rates (aOR, 1.84; 95%CI, 1.08-3.15; P =0.026), clinical pregnancy (adjusted odds ratio (aOR), 1.78; 95% CI, 1.06-2.95; P =0.028) and ongoing pregnancy (aOR, 1.85; 95% CI, 1.09-3.15; P =0.024). The analysis above demonstrated that the smallest number of stromal CD138 + cells suggestive of CE patients requiring treatment was defined as ≥ 3 positive lesions during proliferation.Conclusions：Different diagnostic criteria for CE should be set up in both proliferative and mid-luteal phases. The analysis above demonstrated that the smallest number of stromal CD138 + cells suggestive of CE patients was defined as ≥ 3 positive lesions during the proliferative phase.