Incidence and factors associated with intrauterine adhesions: An Australian population‐based longitudinal study

INTRODUCTION: Intrauterine adhesions (IUAs) describe a condition characterized by scar tissue that forms inside the uterus, which is associated with menstrual irregularities, infertility, and pregnancy loss. In the general population, the incidence of IUAs is largely unknown, as well as associated sociodemographic factors and other menstrual symptoms. This study aims to estimate the incidence of IUAs in the general population and explore the associated sociodemographic factors and menstrual symptoms. MATERIAL AND METHODS: Data from the Australian Longitudinal Study on Women's Health (ALSWH) was used. Women born in 1973-1978 were followed up from 1996 to 2021. The occurrence of IUAs was identified through hospital admissions and other health service records. The cumulative incidence and 5-year incidence of reported IUAs with confidence intervals (CIs) were calculated using exact methods and the Poisson regression models, respectively. Log-binomial models were used to assess the association between individual factors and reported IUAs. RESULTS: Among the 13 133 women who were followed up from a median age of 20.7 years to 47.1 years, 2.7% (95% CI: 2.4-3.0%) had reported IUAs. The incidence rates of IUAs were below 5/10 000 person-years for women aged < 30 and increased from 11.8/10 000 person-years (95% CI: 9.4-14.7) to 15.7/10 000 person-years (95% CI: 12.9-19.1) among women aged 31-35 to those aged 41-45, respectively. Women living in metropolitan areas (Risk Ratio [RR] = 1.47, 95% CI: 1.15-1.87), having private health insurance (RR = 3.29, 95% CI: 2.49-4.35), experiencing severe period pain sometimes or often (RR = 1.76, 95% CI: 1.32-2.34 or RR = 1.92, 95% CI: 1.37-2.68, respectively) or heavy periods sometimes or often (RR = 1.65, 95% CI: 1.25-2.18 or RR = 1.92, 95% CI: 1.39-2.65, respectively) were more likely to have recorded IUAs. CONCLUSIONS: In this national cohort, around one in 40 women had a report of IUAs, which was associated with better access to health services and menstrual symptoms. These findings clarify health issues related to IUAs and lay the groundwork for future studies.