Trajectories of Maternal Urinary Iodine Concentration Are Associated With Gestational Diabetes Mellitus

ABSTRACT Objectives The relationship between iodine status and gestational diabetes mellitus (GDM) is inconclusive. This study aimed to explore the trajectories of urinary iodine concentrations (UIC) in pregnant women before GDM diagnosis and to assess the associations between maternal UIC trajectories and the risk of developing GDM. Methods A prospective cohort study was conducted in China. Data from 1076 pregnant women who were recruited between August 2019 and December 2021 were analyzed. GDM screening was performed at the 28th week of pregnancy. Arsenic and cerium catalysis spectrophotometry was used to measure UIC. The latent class model was used to identify distinct UIC trajectories in pregnant women, using multiple urine specimens. We evaluated the association of UIC trajectories with the risk of GDM by logistic regression analysis. Results Three maternal UIC trajectories were identified: (1) high‐stable trajectory (72.12%), (2) high‐decreasing trajectory (3.07%), and (3) low‐stable trajectory (24.81%). Compared with the pregnant women in high‐stable trajectory group, women in the low‐stable UIC trajectory group showed an increased risk of GDM before adjustment of covariates (OR: 1.58, 95% CI: 1.08–2.27). After adjusting for different covariates, a statistically significant association was observed only between low‐stable trajectory trajectories and GDM. Conclusions This study highlights a relationship between UIC and the risk of GDM. To better prevent iodine deficiency and GDM, persistent sufficient iodine status from pregnancy to delivery, should be emphasized.