Neonatal uterine bleeding: Risk factors and its association with endometriosis-related symptoms later in life

•Longer gestational age, younger maternal age, and overweight baby were the high-risk factors for the occurrence of neonatal uterine bleeding (NUB).•Our web-based survey results indicate that NUB + cases may manifest some symptoms suggestive of endometriosis in adult life. We examined the prevalence and risk factors in association with neonatal uterine bleeding (NUB) by retrospective search of contemporary and historical medical records and investigated the possible association between the history of NUB at birth and endometriosis-related symptoms later in life who are now young women. This was a retrospective case-controlled cohort study and prospective evaluation of web-based questionnaire survey on symptoms related to endometriosis among young women born with and without NUB. Multiple regression analysis was performed incorporating various confounding variables that may influence the occurrence of NUB or the reporting of endometriosis symptoms later in life. Among the 1093 female neonates born between 1996 and 2000, 105 of them had NUB, yielding with a prevalence of 9.6 %. Of the 807 female babies born between 2013 and 2017, 25 (3.1 %) had NUB. 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 of ≥ 40 weeks (OR = 4.54, 95 % CI = 2.20–9.39, P