(A223) Gestational Age’s Impact on the Incidence of Postpartum Thyroiditis

Introduction: Postpartum thyroiditis is an autoimmune disease occurring within a year of delivery in the absence of a history of thyroid disease. While there is evidence that gestational age influences fetal thyroid hormone levels, the association between gestational age and postpartum thyroiditis remains underexplored. This study aimed to evaluate the relationship between preterm delivery (PTD) and full-term delivery (FTD) within postpartum thyroiditis incidence using a large-scale national database.

Methods: A retrospective study was conducted in the TriNetX database. Queries targeted female patients aged 18 to 45 with a PTD or FTD. Demographics, comorbidities, and diagnosis of postpartum thyroiditis, defined as thyroiditis occurring within 1 year post-delivery, were extracted using relevant ICD-10 codes. Propensity score matching was used to adjust the cohorts for differences in demographics and comorbidities.

Results: 689,181 patients were identified; 103,515 (15.0%) with PTD and 580,614 (85.0%) with FTD. PTD patients were slightly older (mean age=29.3, SD=5.9) than FTD patients (mean age=29.1, SD=5.7), and more likely to be Black or African American (21.0% vs. 17.2%, p<.001). PTD patients also had higher rates of diabetes mellitus (12.9 vs. 8.8%, p<.001) and endocrine, nutritional, and metabolic diseases (27.3% vs. 23.7%, p<.001). After propensity score matching, 103,515 patients were retained in each cohort. Outcome analysis revealed no significant difference in postpartum thyroiditis between PTD and FTD patients (p=.757).

Conclusions: In this study, preterm delivery was not found to be associated with an increased risk of postpartum thyroiditis. These findings underscore the need for further research to explore other potential contributors to postpartum thyroiditis.