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Updated: Aug 16, 2026

Modeling Ascending Vaginal Infection, Preterm Birth, and Neonatal Morbidity in Mice
Published on: October 10, 2025
Endometrial microbial colonization and plasma cell endometritis after spontaneous or indicated preterm versus term
William W Andrews1, Robert L Goldenberg, John C Hauth
1Department of Obstetrics and Gynecology, Center for Research in Women's Health, University of Alabama at Birmingham, Birmingham, AL, USA.
Objective:
This study was undertaken to determine whether endometrial microbial colonization or plasma cell endometritis is increased after spontaneous versus indicated preterm delivery or a spontaneous term delivery.
Study Design:
Postpartum, endometrial specimens were obtained after a spontaneous (mean 83, +/- 17.6 days) or indicated (mean 83, +/- 16.7 days) preterm delivery before 34 weeks' gestation and after a spontaneous term delivery (mean 82, +/- 15.7 days; P=.980). Cultures for aerobic and anaerobic bacteria, Trichomonas vaginalis, and genital mycoplasmas were performed. Histologic endometritis was defined as the presence of plasma cells.
Results:
The study population (n=820) was 71% black, 29% white, 69% unmarried, and 31% had less than 12 years of education. Endometrial cultures were positive for at least 1 microorganism in 82% of the women. No significant difference in positive endometrial cultures were observed among women after a spontaneous versus an indicated preterm delivery (85% vs 79%, P=.102), or a spontaneous preterm versus a spontaneous term delivery (85% vs 81%, P=.123). Plasma cell endometritis was present in 39% of 506 specimens sufficient for histologic examination and was also similar in the three groups (P=.160).
Conclusion:
Microbial colonization of the endometrium and plasma cell endometritis are similar 3 months after spontaneous or indicated preterm or term births. Therefore, chronic infection and inflammation of the endometrium (documented at 3 months postpartum) do not appear to be risk factors for subsequent delivery in women with a prior spontaneous delivery less than 34 weeks' gestation.
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