Association between adenomyosis and late miscarriage: a retrospective cohort study

Background Adenomyosis is increasingly diagnosed in women of reproductive age due to advances in imaging and standardised criteria. Beyond its gynaecological symptoms, emerging evidence suggests associations with adverse obstetric outcomes. While associations with placental disorders including placenta praevia and placenta accreta spectrum (PAS) are often reported, the impact of adenomyosis on late miscarriage remains poorly defined. This study primarily evaluated the relationship between adenomyosis and late miscarriage, and secondarily other obstetric complications, especially placental disorders.

This single-centre retrospective cohort study included all singleton deliveries at OBGYN Department from CHU Liège – Citadelle Hospital (Belgium) between January 2020 and December 2023. Pregnancies with predefined complications were identified from institutional delivery registry and paired with temporally adjacent uncomplicated deliveries to construct an outcome-enriched cohort. Adenomyosis was diagnosed based on transvaginal ultrasonography (applying Morphological Uterus Sonographic Assessment (MUSA) criteria) and/or magnetic resonance imaging (MRI) reports, assessed up to six weeks postpartum. Multivariate logistic regression estimated the association between adenomyosis and late miscarriage, adjusted for endometriosis, mode of conception and congenital uterine malformations.

A total of 2620 singleton deliveries were analysed, including 86 cases of adenomyosis (3.3%). Women with adenomyosis were older and more frequently conceived using assisted reproductive technologies. Adenomyosis was associated with higher odds of overall obstetric morbidity (OR 1.64, 95%CI: 1.06–2.55, p = 0.03). The odds of late miscarriage were significantly higher in adenomyosis group (OR 3.88, 95%CI: 1.62–9.34, p = 0.0077) and remained independently associated after adjustment (aOR 2.95, 95%CI: 1.04 − 7.15, p = 0.043). Adenomyosis was also associated with increased odds of PAS (OR 2.44, 95%CI: 1.15–5.20, p = 0.026) and placenta praevia (OR 3.48, 95%CI: 1.21–10.03, p = 0.037).

Adenomyosis was independently associated with late miscarriage in this cohort. Given that adenomyosis-related alterations, including ectopic endometrium within myometrium, chronic inflammation, impaired uterine contractility and abnormal vascular remodelling, may impair placental development, affected pregnancies may benefit from increased clinical awareness and careful antenatal surveillance, particularly during second trimester. Further prospective studies using pre-conception standardised imaging and detailed phenotyping are needed to clarify underlying mechanisms and optimise clinical management. Trial registration not applicable. Similar content being viewed by others Abbreviations - ACOG: - American College of Obstetricians and Gynaecologists - aOR: - adjusted odds ratio - ART: - assisted reproductive techniques - BMI: - body mass index - CI: - confidence interval - EBL: - estimated blood loss - FAOM: - focal adenomyosis of the outer myometrium - HELPP: - haemolysis - elevated liver enzymes and low platelet count syndrome - ISSHP: - International Society for the Study of Hypertension in Pregnancy - ISUOG: - International Society of Ultrasound in Obstetrics and Gynaecology - IUGR: - intrauterine growth restriction; IUI: intrauterine insemination - IVF: - in vitro fertilisation - JZ: - junctional zone - MUSA: - Morphological Uterus Sonographic Assessment - OR: - Odds ratio - PAS: - placenta accreta spectrum - PPH: - post-partum haemorrhage - PPROM: - preterm premature rupture of membranes - RR: - relative risk - SGA: - small gestational for age - WHO: - World Health Organization

The authors thank the participants of this study. Funding Not applicable. Author information Authors and Affiliations Corresponding author Ethics declarations Ethics approval This study was conducted in accordance with the ethical principles of the Declaration of Helsinki. Ethical approval was granted by the Ethics Review Committee of Citadelle Hospital, Liège, Belgium (Reference No. 412–2318). The requirement for written informed consent was formally waived by the Ethics Review Committee, which determined that obtaining consent was not required under the applicable Belgian regulatory framework, considering the retrospective design of the study, the use of existing medical records, the absence of any intervention, and the adherence to an institutional opt-out procedure without any registered patient objection. No patient contact occurred, no intervention was performed, and no additional data were collected for research purposes. Data were processed in accordance with the General Data Protection Regulation (Regulation (EU) 2016/679 of 27 April 2016), including Article 9(2)(j), and the Belgian Law of 30 July 2018 on the protection of natural persons regarding the processing of personal data. Data were anonymized prior to analysis, and no identifiable patient information is reported in this manuscript. 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 4.0 International License, which permits use, sharing, adaptation, 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 changes were made. 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/4.0/. About this article Cite this article Timmermans, M., El Sayed, S., Mélotte, S. et al. Association between adenomyosis and late miscarriage: a retrospective cohort study. BMC Pregnancy Childbirth (2026). https://doi.org/10.1186/s12884-026-10024-4 Received: Accepted: Published: DOI: https://doi.org/10.1186/s12884-026-10024-4