Association between neonatal uterine bleeding and endometriosis-related symptoms later in life

Abstract Neonatal uterine bleeding (NUB) has been postulated to cause early-onset endometriosis, but so far there has been no information on whether young women with a history of NUB may manifest various symptoms related to endometriosis. In this retrospective case-controlled cohort study, we investigated the prevalence and risk factors of NUB and prospectively evaluated endometriosis-related symptoms by web-based questionnaire survey. Among 807 female babies born at our hospital between 2013 and 2017, NUB occurred in 25 cases with a prevalence of 3.1%. Multiple Logistic regression analysis indicated that younger age of the mother [odds ratio (OR) 0.92, 95% confidence interval (CI) 0.85-1.00, P = 0.048] and longer gestational age of 39 weeks (OR 3.04, 95% CI 1.43–6.45, P = 0.004) and ≥ 40 weeks (OR 4.54, 95% CI 2.20–9.39, P < 0.0001) of gestation were significantly associated with the occurrence of NUB. We confirmed the validity of the reported prevalence and risk factors of NUB. Young mothers and longer gestational age are the risk factors for NUB and newborn females with or without NUB similarly suffer from various endometriosis-related symptoms later in life during adulthood. Future prospective cross-sectional study is warranted to confirm the endometriosis-related symptoms in NUB + and NUB- cases by physical examination, ultrasound and/or MRI.