Background <p>Limited research exists on the obstetric risk profiles of women in same-sex relationships (WSSR) undergoing childbirth.</p> Methods <p>Population-based cohort study including deliveries in the Swedish Stockholm-Gotland regions, January 2008-June 2020. Linkage with national health and quality registers provided data on relationships status. Characteristics of WSSR were compared with those of women in different-sex relationships.</p> Results <p>Of the 289 979 included deliveries, 1 292 (0.45%) were to WSSR. Compared to women in different-sex relationships, WSSR were more likely to be older, nulliparous, of Swedish origin, and have higher educational attainment. Assisted reproduction was reported for 87.5% of WSSR, versus 7.2% in the comparison group. Smoking during pregnancy was less common for WSSR (1.2% vs. 3.8%). Adjusting for parity and age, WSSR were more likely to be overweight in early pregnancy (adjusted odds ratio [aOR] 1.47; 95% CI 1.30–1.67). Furthermore, they were more likely to have received support for fear of childbirth (12.2% vs. 9.7%; aOR 1.48 95% CI 1.14–1.91). Self-rated pre-pregnancy health and history of major medical conditions were largely similar across both groups, although WSSR were more likely to have been diagnosed with thyroid conditions, rheumatic diseases, gynecological conditions and psychiatric illnesses.</p> Conclusions <p>When undergoing childbirth, WSSR more often presented with obstetric risk factors including higher age, nulliparity, and overweight. However, they were also more likely to have higher educational attainment and less likely to report smoking. Pre-pregnancy medical conditions were largely similar between groups. Even so, psychiatric disease and support for fear of childbirth were more common in WSSR, highlighting the need for targeted support during pregnancy.</p>