Histological diagnosis of endometriosis and adenomyosis in relation to obstetric outcomes: a Dutch population-based cohort study.

OBJECTIVE: To assess the prevalence of obstetric and neonatal complications in pregnancies of women with histologically confirmed endometriosis, adenomyosis, or both, compared with the general Dutch population. METHODS: In this retrospective population-based cohort study, nationwide Dutch data from 1995 to 2018 were analysed. Pregnancies were identified through the PALGA pathology database and the Perined perinatal registry, including 19,418 pregnancies in women with endometriosis only (EO), 11,724 with adenomyosis only (AO), and 1,048 with both conditions (EA), with adenomyosis diagnoses being made at hysterectomy. Outcomes were compared with 4,065,165 pregnancies from the general Dutch population. Multivariable logistic regression was used to estimate adjusted odds ratios (aORs) and 95% confidence intervals (CIs), controlling for maternal, obstetric, and socioeconomic factors. The primary outcome was preterm birth (PTB; <37 weeks' gestation). Secondary outcomes included placental complications, mode of delivery, neonatal intensive care unit (NICU) admission, and selected maternal and neonatal outcomes. RESULTS: All disease groups had an increased risk of PTB, highest in the EA group (aOR 1.53, 95% CI 1.30-1.86), followed by EO (aOR 1.43, 95% CI 1.37-1.50) and AO (aOR 1.26, 95% CI 1.19-1.34). Histological diagnosis of endometriosis, adenomyosis, and combined disease were also associated with higher risks of placental complications, caesarean delivery, and NICU admission. Endometriosis was additionally associated with placental abruption, foetal distress, and perinatal death. Adenomyosis was linked to miscarriage, pre-eclampsia, threatened preterm birth, placental retention, and postpartum haemorrhage. Combined disease showed particularly high risks of placenta praevia and endometritis. CONCLUSIONS: Histologically confirmed endometriosis and adenomyosis are associated with an increased risk of preterm birth, as well as several other adverse obstetric and neonatal outcomes, with differing complication profiles between disease phenotypes. These findings support future research into phenotype-specific risk stratification and tailored antenatal care.