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. METHODS: 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. RESULTS: 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. CONCLUSION: SPL is notably associated with the JZ characteristics and adenomyosis. Further studies are recommended to explore the relationship between these factors and pregnancy outcomes.