Abstract
IMPORTANCE: Evidence suggests that aberrant uterine contractility in nonpregnant women with endometriosis and adenomyosis contributes to symptoms and potentially heralds their pathogenesis. However, uterine peristalsis remains understudied, inconsistently measured, and poorly understood. OBJECTIVE: To summarize evidence on uterine contractility across the menstrual cycle phases in women with endometriosis and adenomyosis. DATA SOURCES: PubMed/MEDLINE, Embase, and Scopus databases searched up to May 2, 2024. STUDY SELECTION AND SYNTHESIS: Observational studies compared quantitative measures of uterine contractility using magnetic resonance imaging, ultrasound, electrophysiology, or direct intrauterine pressure recording across different menstrual cycle phases between women with endometriosis/adenomyosis and controls on the basis of predefined problem/population, intervention, comparison, and outcome criteria. Study quality was assessed using the Newcastle-Ottawa Scale. Pooled estimates for primary (risk ratios with 95% confidence intervals [CIs]) and secondary (mean difference [MD] with 95% CIs) outcomes were calculated using random-effects models. MAIN OUTCOMES: Pooled risk of retrograde menstruation uterine contraction pattern in cases vs. controls; pooled MD in continuous measures of uterine contractility (frequency, amplitude, and velocity of contractions) across all the menstrual cycle phases in cases vs. controls. RESULTS: Nine studies met the inclusion criteria; most were studies that evaluated women with endometriosis. An increased risk of retrograde uterine contractions during menstruation was observed in women with endometriosis compared with that in controls (risk ratio, 8.63; 95% CI, 3.24-22.95; I(2), 0). The pooled MDs in contraction frequency between cases and controls were 0.82 (95% CI, 0.13-1.52; I(2), 18.61%) in the menstrual phase and 0.52 (95% CI, 0.22-0.83; I(2), 27.18%) in the luteal phase. Results for the follicular and periovulatory phases were more heterogeneous. Higher contraction amplitudes in women with endometriosis or adenomyosis were reported across all menstrual cycle phases. Because of the paucity of data, especially for adenomyosis, evidence certainty was graded as low for most comparisons. CONCLUSION AND RELEVANCE: The approximately ninefold increased risk of retrograde pattern during menstruation in endometriosis supports the potential role of retrograde menstruation in its etiopathogenesis. Abnormal uterine contractility, likely not limited to the menstrual phase, may be a mechanical factor contributing to development of endometriosis and related symptoms, including menstrual pain and infertility, with limited, mostly concordant evidence for adenomyosis. REGISTRATION NUMBER: PROSPERO ID CRD42024512273-accepted on February 23, 2024.