Effects of Autoimmune Thyroiditis on Pregnancy Outcomes: Analysis of the Nationwide Inpatient Sample, 2016–2020

Purpose: To assess whether autoimmune thyroiditis is associated with obstetric, perinatal, and fetal complications in a nationally representative population of pregnant women. Methods: This retrospective study utilized data from the U.S. Nationwide Inpatient Sample (NIS) and included women aged ≥ 18 years with delivery-related hospitalizations between 2016 and 2020. Patients were categorized based on the presence/absence of autoimmune thyroiditis. Propensity score matching was applied to balance baseline characteristics. Associations between autoimmune thyroiditis and adverse outcomes were assessed using multivariable logistic regression analysis. Results: Among 3.76 million delivery-related hospitalizations, 17 716 were included. Autoimmune thyroiditis was independently associated with increased risk of gestational diabetes (adjusted odds ratio [aOR] = 1.10, 95% CI: 1.01-1.20), preeclampsia (aOR = 1.22, 95% CI: 1.08-1.38), induction of labor (aOR = 1.18, 95% CI: 1.09-1.26), failed induction of labor (aOR = 1.36, 95% CI: 1.07-1.72), abnormal fetal heart rate or rhythm (aOR = 1.15, 95% CI: 1.06-1.25), and fetal growth restriction (aOR = 1.33, 95% CI: 1.12-1.59). Associations were more pronounced in women younger than 35 years. Conclusions: Autoimmune thyroiditis is associated with modest increases in adverse pregnancy risk and may inform risk assessment and individualized clinical monitoring.