Objective To analyze the factors influencing iodine nutritional status in pregnant women during pregnancy， based on thyroid function and thyroid autoantibody levels， and to explore the association between iodine nutritional abnormalities and pregnancy outcomes. Methods A total of 838 pregnant women who underwent routine prenatal checkups at Qinghai Provincial People's Hospital between January 2021 and June 2023 were prospectively enrolled in this study. All participants were followed until delivery. Seven cases were lost to follow-up， resulting in a final sample size of 831 participants. Among them， 276 were in the first trimester， 384 in the second trimester， and 171 in the third trimester. Data on urinary iodine concentration （UIC）， urinary creatinine （UCr）， thyroid function indicators， and thyroid autoantibodies were collected. Based on their iodine nutritional status， the participants were categorized into either the iodine-sufficient group or the iodine-abnormal group （including iodine-deficient， iodine-hyper-sufficient， and iodine-excessive subgroups）. This study analyzed the iodine nutritional status of pregnant women during different gestational periods， compared thyroid function indices， prevalence of thyroid diseases， and the positivity rates of thyroid peroxidase antibody （TPOAb）， thyroglobulin antibody （TGAb）， and thyroid-stimulating hormone receptor antibody （TRAb） among different iodine status groups. Additionally， adverse pregnancy outcomes were compared across groups. Multivariate logistic regression analysis was conducted to identify risk factors associated with iodine abnormalities during pregnancy， and a predictive model was developed to assess its potential predictive value. Results Among the 831 pregnant women included in the study， 373 cases （44.89%） exhibited iodine sufficiency， while 458 cases （55.11%） presented with iodine abnormalities， including 282 cases of iodine deficiency， 144 cases of iodine hypersufficiency， and 32 cases of iodine excess. No statistically significant differences were observed in the iodine nutritional status across different trimesters （P > 0.05）. The serum level of thyroid-stimulating hormone （TSH） was significantly higher in the iodine abnormal group compared to the iodine sufficient group （P < 0.05）. Additionally， the iodine abnormal group demonstrated higher positivity rates of TPOAb alone， TGAb， and TRAb， as well as increased incidence of thyroid dysfunction and total adverse pregnancy outcomes compared to the iodine sufficient group （all P < 0.05）. These adverse indicators were also significantly elevated in the iodine-deficient， iodine super-sufficient， and iodine overdose subgroups compared to the iodine sufficient group （P < 0.05）. Elevated serum TSH levels and the presence of TPOAb， TGAb， and TRAb were identified as risk factors for iodine abnormalities during pregnancy （P < 0.05）. The predictive model constructed for identifying iodine abnormalities in pregnant women demonstrated an area under the curve （AUC） of 0.876， with a sensitivity of 72.27% and a specificity of 89.01%. Conclusions The prevalence of iodine nutritional abnormalities among pregnant women during pregnancy was high， with most cases presenting iodine deficiency. These abnormalities were associated with thyroid function， thyroid autoimmunity， and pregnancy outcomes， but showed no significant correlation with gestational age. Furthermore， the prediction model developed based on identified risk factors demonstrated effective performance in predicting iodine nutritional abnormalities during pregnancy.