Effect of Iodine Nutrition Status on Thyroid Function and Pregnancy Outcomes

Abstract

BackgroundIodine is essential for normal thyroid function, supporting healthy fetal and child development. The relevance between maternal iodine nutrition status and pregnancy outcomes remains controversial. The aim was to explore whether urinary iodine concentrations(UIC)/urinary creatinine(UCr) was associated with thyroid function and adverse pregnancy outcomes. MethodsThis study was performed in the Department of Endocrinology and Metabolism of the First A liated Hospital of Nanjing Medical University. A total of 212 pregnant women was enrolled from May 2018 to November 2021 from the rst visit until postpartum. Maternal serum samples were obtained in the second trimester and then thyroid-stimulating hormone (TSH), free thyroxine (FT4), free triiodothyronine (FT3), urinary iodine concentrations(UIC), and urinary creatinine (UCr) were tested. The correlation of UIC/UCr, which represented maternal iodine nutrition status, with TSH, FT4, and FT3 was studied using linear regression. And we assessed associations between UIC/UCr and pregnancy outcomes. Notably, we explored consistency between UIC/UCr and the incidence of low birth weight (LBW) by application of logistic regression analysis. ResultsA total of 212 women were divided into 3 groups according to the upper and lower quartiles of UIC/UCr . There were 53 women in Group1 (UIC/UCr<106.96ug/g), 106 women in Group2 (UIC/UCr 106.96-259.08 ug/g), and 53 women in Group3 (UIC/UCr >259.08ug/g). The level of UIC/UCr had negative correlation with FT4 (r=-0.139, p=0.043) but positive correlation with TSH (r=0.096, p=0.162>0.05). There was a signi cant difference in the incidence of LBW among 3 groups (p=0.007). Logistic regression analysis found that the level of UIC/UCr was an independent factor for LBW (p=0.048, OR=0.991, 95%CI (0.982,0.999)). The receiver operating characteristic (ROC) curve showed that the area under the curve (AUC) for UIC/UCr predicting the incidence of low birth weight was 0.687 (p=0.013, 95%CI 0.575, 0.799). ConclusionsLower UIC/UCr during pregnancy was associated with higher FT4 and lower TSH. And iodine de ciency during pregnancy is a risk factor for low birth weight. Our ndings indicated that more attention should be paid to the appropriate iodine nutrition status in pregnant women, which can help prevent suffering from adverse pregnancy outcomes.