Reproductive
Sexual Orientation Disparities in Pregnancy Loss: A Meta-Analysis of Three Longitudinal Cohorts Colleen A Reynolds* Colleen Reynolds Payal Chakraborty Tabor Hoatson Jarvis T. Chen Lori Chibnik Janet-Rich-Edwards Brittany M. Charlton
Background: Emerging research suggests sexual minority women may be at an increased risk of pregnancy loss, but these studies have adjusted for potential mediators and have not included certain subgroups (i.e., “mostly heterosexual” women).
Methods: We used data from three longitudinal cohorts: the Nurses’ Health Study 2 and 3 and Growing Up Today Study (N=235,150 pregnancies from 85,547 participants). In each cohort, participants reported lifetime pregnancies and whether each pregnancy ended in an induced abortion, loss (miscarriage <20 weeks, stillbirth ≥20 weeks), ectopic/tubal, or livebirth, as well as their sexual orientation. We used log-binomial generalized estimate equation models to compare the risk of pregnancy loss among pregnancies to completely heterosexual participants (reference) to those among heterosexual participants with same-sex attractions/partnerships, mostly heterosexual, bisexual, and lesbian participants. To address confounding, selection, and multiple pregnancies per participant, models were weighted by the product of inverse probability of treatment, inverse probability of censoring, and inverse cluster size weights. Cohort-specific results were combined using fixed-effects meta-analysis.
Results: Pregnancies among heterosexual participants with same-sex attractions/partnerships (RR:1.07; 95%CI:1.02–1.13) as well as those among mostly heterosexual (1.27; 1.20–1.35), bisexual (1.50; 1.29–1.75), and lesbian (1.70; 1.45-1.99) participants were more likely to end in a loss than those to completely heterosexuals. Notably, risk of stillbirth was elevated among pregnancies to lesbian (3.48; 2.05–5.90) participants compared to those among completely heterosexuals; stillbirth risk was not elevated among other sexual minority subgroups.
Conclusion: Future research must examine mechanisms of sexual orientation-related inequities in pregnancy loss (e.g., heterosexism, maternal age, use of medically assisted reproduction, preconception health).
