BACKGROUND: Many sexual and/or gender minority individuals build families through pregnancy and childbirth, but it is unknown whether they experience different clinical outcomes than those who are not sexual and/ or gender minority individuals. OBJECTIVE: To evaluate obstetrical and birth outcomes comparing couples who are likely sexual and/or gender minority patients compared with those who are not likely to be sexual and/or gender minority patients. STUDY DESIGN: We performed a population-based cohort study of live birth hospitalizations during 2016 to 2019 linked to birth certificates in California. California changed its birth certificate in 2016 to include gender-neutral fields such as "parent giving birth" and "parent not giving birth," with options for each role to specify "mother," "father," or "parent." We classified birthing patients in mother-mother partnerships and those who identified as a father in any partnership as likely sexual and/or gender minority and classified birthing patients in mother-father partnerships as likely not sexual and/or gender minority. We used multivariable modified Poisson regression models to estimate the risk ratios for associations between likely sexual and/or gender minority parental structures and outcomes. The models were adjusted for sociodemographic factors, comorbidities, and multifetal gestation selected by causal diagrams. We replicated the analyses after excluding multifetal gestations. RESULTS: In the final birthing patient sample, 1,483,119 were mothers with father partners, 2572 were mothers with mother partners, and 498 were fathers with any partner. Compared with birthing patients in mother-father partnerships, birthing patients in mother-mother partnerships experienced significantly higher rates of multifetal gestation (adjusted risk ratio, 3.9; 95% confidence interval, 3.4-4.4), labor induction (adjusted risk ratio, 1.2; 95% confidence interval, 1.1-1.3), postpartum hemorrhage (adjusted risk ratio, 1.4; 95% confidence interval, 1.3-1.6), severe morbidity (adjusted risk ratio, 1.4; 95% confidence interval, 1.2-1.8), and nontransfusion severe morbidity (adjusted risk ratio, 1.4; 95% confidence interval, 1.1-1.9). Severe morbidity was identified following the Centers for Disease Control and Prevention "severe maternal morbidity" index. Gestational diabetes mellitus, hypertensive disorders of pregnancy, cesarean delivery, preterm birth (<37 weeks' gestation), low birth-weight (<2500 g), and low Apgar score (<7 at 5 minutes) did not significantly differ in the multivariable analyses. No outcomes significantly differed between father birthing patients in any partnership and birthing patients in mother-father partnerships in either crude or multivariable analyses, though the risk of multifetal gestation was nonsignificantly higher (adjusted risk ratio, 1.5; 95% confidence interval, 0.9-2.7). The adjusted risk ratios for the outcomes were similar after restriction to singleton gestations. CONCLUSION: Birthing mothers with mother partners experienced disparities in several obstetrical and birth outcomes independent of sociodemographic factors, comorbidities, and multifetal gestation. Birthing fathers in any partnership were not at a significantly elevated risk of any adverse obstetrical or birth outcome considered in this study.
