Emerging evidence links structural sexism and structural discrimination against lesbian, gay, and bisexual (LGB) populations to poor health outcomes, but studies have yet to examine the combined effects of these mutually reinforcing systems of inequality. Therefore, we developed a composite measure of structural heteropatriarchy—which includes state-level LGB policies, family planning policies, and indicators of structural sexism (e.g., women's political and economic position relative to men)—and examined its relationship to birth outcomes using data from Waves I to V of the National Longitudinal Study of Adolescent to Adult Health. Multivariate regression analyses demonstrated that higher levels of heteropatriarchy were associated with an increased risk of preterm birth and decreased birth weight, net of important covariates. There was no association between clinical low birth weight and heteropatriarchy, or interactions between heteropatriarchy and individuals' race, ethnicity or sexual identity, suggesting a negative effect of heteropatriarchy on birth outcomes for all pregnant people. This study demonstrates the importance of considering gender and sexuality as mutually reinforcing systems of oppression that impact population health. Future research should examine the impact of heteropatriarchy on additional health outcomes and in conjunction with other structural inequalities such as racism and transgender oppression.