New-onset mental illness among gestational carriers

Importance — Pregnancy is a period of increased vulnerability for psychological well-being. The mental health of gestational carriers is understudied.

Objective — To study the association between gestational carriage and new-onset mental illness.

Design, setting, and participants — This population-based, retrospective cohort study included all women from the entire province of Ontario, Canada, without known mental illness before pregnancy and who gave birth at greater than 20 weeks’ gestation from April 1, 2012, to March 31, 2021. Data were analyzed from September 10, 2024, to May 23, 2025.

Exposures — Gestational carriers were contrasted with non–gestational carriers who conceived unassisted (comparison 1) or by in vitro fertilization (IVF) (comparison 2).

Main outcomes and measures — The main outcome was a diagnosis of new-onset mental illness based on 2 or more outpatient visits or 1 or more emergency department visit or hospital admission and occurring from the estimated date of conception up to a maximum follow-up date of March 31, 2024. Modified Poisson regression–generated incidence rate ratios (IRRs) adjusted for maternal age, income quintile, urban residence, obesity, smoking, parity, and chronic hypertension.

Results — Of 767 406 eligible pregnancies in women (mean [SD] age, 30.5 [5.1] years), 748 732 (97.6%) were by unassisted conception, 17 916 (2.3%) by IVF, and 758 (0.1%) by gestational carriage. Gestational carriers were more likely than unassisted conception and IVF carriers to be parous (91.2% vs 57.9% and 34.1%, respectively), reside in a lower-income area (23.4% vs 21.9% and 12.1%, respectively), and have higher rates of obesity (36.1% vs 17.0% and 17.1%, respectively) and chronic hypertension (3.2% vs 1.6% and 2.9%, respectively). The median (IQR) follow-up was 4.5 (2.3-7.2) years. In comparison 1, new-onset mental illness occurred in 236 gestational carriers (6.9 per 100 person-years) vs 195 022 women with unassisted conception (5.2 per 100 person-years) (adjusted IRR, 1.43; 95% CI, 1.26-1.63). In comparison 2, new-onset mental illness occurred among 236 gestational carriers (6.9 per 100 person-years) and 4704 women receiving IVF (5.0 per 100 person-years) (adjusted IRR, 1.29; 95% CI, 1.13-1.47).

Conclusions and relevance — The findings of this cohort study suggest that gestational carriers were more likely to be diagnosed with mental illness during and after pregnancy. Mental health screening, counseling, and provision of support may be particularly important in this population.