Comorbidity of endometriosis and adenomyosis: A systematic review examining the impact of co-morbid disease on fertility and pregnancy outcomes

PURPOSE: Endometriosis and adenomyosis are both characterised by ectopic endometrial-like tissue growing outside the endometrium of the uterus, however, they are ultimately distinct diseases with different pathophysiological mechanisms. Endometriosis and adenomyosis both have negative impacts on fertility and pregnancy outcomes. Women often have both conditions simultaneously, however, the reproductive burden of comorbid endometriosis and adenomyosis remains relatively unknown. This systematic review aims to investigate the effects of comorbid endometriosis and adenomyosis on fertility and pregnancy outcomes as compared to neither disease, or both in isolation. METHODS: A systematic review was performed in line with PRISMA guidelines using PubMed and EMBASE search engines for papers published between 2000-2024, which evaluated fertility and/or pregnancy outcomes in adult females with endometriosis and/or adenomyosis. Risk of bias was also evaluated. RESULTS: The captured literature reported clinical pregnancy rates (6 studies) and live birth rates (4 studies) were significantly reduced by comorbid endometriosis and adenomyosis. However, inconsistent results were demonstrated for the impact of comorbidity on various pregnancy outcomes, including ectopic pregnancy, miscarriage, pre-eclampsia, placenta praevia, preterm birth and small for gestational age. CONCLUSION: Women with endometriosis and adenomyosis combined, may be at a higher risk of poor fertility, low pregnancy rates and possible obstetric complications, which may be due to the cumulative effects of both conditions.