Effects of adenomyosis and endomyometrial junctional zone on spontaneous preterm labor : a case-control study

Background Spontaneous preterm labor (SPL) is a significant obstetric concern, and recent literature suggests an association with adenomyosis. In this study, we compared adenomyosis and endomyometrial junctional zone (JZ) in women with and without a recent history of SPL.

This case-control study was conducted between October 2019 and Mar 2021. Exclusion criteria included Iatrogenic preterm labor, a history of hormonal drug use after delivery, a history of Müllerian anomaly, endometriosis, fibroids, uterus surgery, cesarean section, and postpartum hemorrhage requiring uterine procedures. The study population consisted of women with a history of SPL or a history of full-term vaginal delivery within the last six months in the study and control groups, respectively. All participants underwent 2- and 3-dimensional transvaginal sonography six months after delivery to assess the JZ thickness and irregularity, and the presence or absence of adenomyosis.

92 women were included in this study. No significant differences were found regarding age, body mass index, parity, or prior preterm birth. The mean JZ irregularity was 2.53 ± 1.39 mm in the study group and 1.86 ± 0.72 mm in the control group (P = 0.004). In the overall cohort, increased JZ difference was associated with higher odds of SPL (aOR = 1.74). Stratifying by adenomyosis status showed that the association was stronger and remained significant in women with adenomyosis (aOR = 1.88), whereas it lost significance in those without adenomyosis.

SPL is notably associated with the JZ characteristics and adenomyosis. Further studies are recommended to explore the relationship between these factors and pregnancy outcomes. Similar content being viewed by others Abbreviations - SPL: - Spontaneous preterm labor - JZ: - Endomyometrial junctional zone - 2D: - Two-dimensional - 3D: - Three-dimensional - TVS: - Transvaginal sonography - MRI: - Magnetic resonance imaging - SD: - Standard deviation - MD: - Mean Difference - BMI: - Body mass index - ORs: - Odds ratios - CI: - Confidence interval Funding This research did not receive any funding. Author information Authors and Affiliations Corresponding author Ethics declarations Ethics approval and consent to participate The study was approved by the Ethics Committee of Tehran University of Medical Sciences, Tehran, Iran (ethics code: IR.TUMS.MEDICINE.REC.1397.956), and written informed consent was also obtained from all the participants. The study was conducted in accordance with the Declaration of Helsinki. Consent for publication Not applicable. Competing interests The authors declare no competing interests. Additional information Publisher’s Note Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations. Rights and permissions Open Access This article is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License, which permits any non-commercial use, sharing, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if you modified the licensed material. You do not have permission under this licence to share adapted material derived from this article or parts of it. The images or other third party material in this article are included in the article’s Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit http://creativecommons.org/licenses/by-nc-nd/4.0/. About this article Cite this article Moini, A., Pirjani, R., Sepidarkish, M. et al. Effects of adenomyosis and endomyometrial junctional zone on spontaneous preterm labor : a case-control study. BMC Pregnancy Childbirth (2026). https://doi.org/10.1186/s12884-026-09209-8 Received: Accepted: Published: DOI: https://doi.org/10.1186/s12884-026-09209-8