Abstract
IMPORTANCE: Sexual minority individuals have less access to high-quality reproductive health care-including contraceptive care-and have higher rates of unintended pregnancies than their heterosexual peers. Little is known about differences in abortion use by sexual orientation. OBJECTIVE: To quantify differences in abortion use by sexual orientation. DESIGN, SETTING, AND PARTICIPANTS: This study using data from 3 North American cohorts included pregnancies between 1959 and 2024. Nurses' Health Study II (NHS2) is a cohort of female nurses in the US, Growing Up Today Study (GUTS) is a cohort of NHS2's offspring, and Nurses' Health Study 3 (NHS3) is a cohort of nurses and nursing students in the US and Canada. EXPOSURE: Sexual orientation (completely heterosexual, heterosexual with same-sex experience, mostly heterosexual, bisexual, and lesbian or gay). MAIN OUTCOME AND MEASURE: Participant-reported pregnancy outcome (induced abortion vs any other pregnancy outcome). RESULTS: Of a total of 235 948 pregnancies (with nonmissing pregnancy outcome data) across 85 640 participants, 211 095 pregnancies (89.5%) were to completely heterosexual participants, and 24 853 (10.5%) were to sexual minority participants. In GUTS and NHS3, there were a higher percentage of pregnancies to sexual minority participants (1546 [17.7%] and 7425 [19.7%], respectively) than in NHS2 (15 882 [8.4%]). In the cohorts combined, 20 243 pregnancies (8.6%) ended with an induced abortion. Compared with pregnancies to completely heterosexual participants, those to sexual minority participants were more likely to end with an induced abortion (risk ratio [RR], 1.93 [95% CI, 1.85-2.02]). Among sexual minority subgroups, heterosexual with same-sex experience (RR, 1.56 [95% CI, 1.47-1.66]), mostly heterosexual (RR, 2.15 [95% CI, 2.03-2.29]), bisexual (RR, 2.84 [95% CI, 2.49-3.23]), and lesbian or gay participants (RR, 2.52 [95% CI, 2.14-2.95]) had higher abortion use. CONCLUSIONS AND RELEVANCE: In this study using data from retrospectively reported pregnancies from 3 longitudinal cohorts, all sexual minority groups had increased abortion use compared with completely heterosexual participants, and abortion use was heterogeneous; given the higher use of abortion among sexual minority populations, they are more likely to be disproportionately impacted by the narrowing of abortion access in the US after the Supreme Court Dobbs decision. Future research is needed to understand the pathways that contribute to the unique abortion care needs of sexual minority individuals, in order to provide adequate support for abortion seekers.