Perceived Psychological Stress and Fecundability among Women Planning Pregnancy: Evidence from a Large Preconception Cohort Study from China

Objective: Evidence on the stress–fecundability relationship is mixed, and both the population heterogeneity and the effects of moderate stress remain understudied. We aimed to investigate the association of stress with fecundability in women planning pregnancy, and to explore whether this association varied by gravidity, health status, or lifestyle factors. Design: Perspective cohort study. Setting: National Free Pre-conception Check-up Project (NFPCP), China Population: 512,735 reproductive-aged women who participated in the NFPCP between 2012 and 2018. Methods: Perceived psychological stress was assessed at enrollment using a two-item questionnaire rated on a 5-point Likert scale. Associations between perceived stress levels and fecundability were estimated using Cox proportional hazards regression models, adjusting for potential confounders. Main outcome measures: Participants were followed every three months for one year or until pregnancy was confirmed by gynecologic ultrasonography, whichever came first. The primary outcome was time to pregnancy. Results: Compared with the no-stress group, fecundability was 2% higher in the moderate-stress group (HR, 1.02; 95% CI, 1.01, 1.03) and 15% lower in the high-stress group (HR, 0.85; 95% CI, 0.81, 0.90). The beneficial effect was specific to moderate stress arising from life and work, whereas financial strain showed no such reproductive advantage. Subgroup analyses revealed that the positive association was more pronounced among women without tobacco exposure or with hyperglycemia (impaired glucose tolerance or diabetes), and the adverse impact of high stress was significantly exacerbated in women with obesity or a history of prior pregnancies. Conclusions: In this large-scale cohort, we identified an inverse U-shaped association where moderate stress from life or work enhanced fecundability. These findings challenge the view that all stress is harmful, offering reassurance that moderate life or work stress is compatible with conception. Nevertheless, high stress levels warrant careful attention, particularly among women with obesity or those with a history of prior pregnancies.