Prevalence of elevated TSH levels and associated factors among pregnant women receiving care at primary care centers in Southern Lima

Introduction. Thyroid disorders are the most common endocrine conditions during pregnancy after diabetes mellitus. Hypothyroidism has been associated with adverse maternal and perinatal outcomes, making early detection essential. In Peru, evidence regarding its prevalence in primary care settings remains limited. Objective. To determine the prevalence of positive screening for elevated TSH and its associated factors in pregnant women treated in primary care centers in South Lima. Methods. An observational, cross-sectional, analytical study was conducted in 358 pregnant women aged ≥18 years attending primary healthcare facilities of the DIRIS Lima Sur in 2025. The dependent variable was serum TSH ≥ 4.0 mIU/L, measured using electrochemiluminescence immunoassay (ECLIA; Elecsys cobas e). Sociodemographic, gynecological-obstetric, and clinical variables were collected. Descriptive, bivariate, and multivariable Poisson regression analyses with robust variance were performed, adjusting for potential confounders. Results. The mean age was 27.75 (standard deviation 6.43 years). The prevalence of positive screening was 9.5% (n = 34). In bivariate analysis, positive screening was associated with higher gestational age (p < 0.01), higher number of medications (p = 0.03), greater number of previous abortions (p = 0.05), and fewer thyroid-related symptoms (p = 0.02). In the multivariable analysis, having at least one abortion (PR = 2.42; 95% CI: 1.25-4.71; p = 0.01) and a gestational age ≥28 weeks (PR = 2.50; 95% CI: 1.195.25; p = 0.01) were associated with a higher probability of elevated TSH. Conclusions. Approximately 1 in 10 pregnant women had elevated TSH levels. These findings contribute to the characterization of its occurrence in this population and provide context-specific evidence from primary care settings in Southern Lima.