Association between serum thallium in early pregnancy and risk of gestational diabetes mellitus: The Ma'anshan birth cohort study

Background: High blood glucose has been noted in case reports of acute thallium poisoning, however, effects of low-level exposure of thallium on risk of gestational diabetes mellitus (GDM) has not been explored yet. Objectives: We aimed to explore the association of serum thallium concentration (STC) in early pregnancy and risk of GDM. Methods: Data of 3013 women from the Ma'anshan birth cohort study (MABC), China was used. STC was measured by inductively coupled plasma mass spectrometry (ICP-MS). Multivariate logistic regression was performed to the association of STC and risk of GDM. Stratified analysis was carried out according to maternal age and pre-pregnancy BMI. Results: We documented 383 incident GDM (12.7%). The STC ranged from 0.011 to 0.232 pg/L with a median of 0.062 pg/L. Women with advanced age and higher pre-pregnancy BMI tended to have higher level of STC. Individuals in GDM-group have higher level of STC than that in non-GDM group (P = 0.007). Maternal STC in early pregnancy was associated with risk of GDM, but the association attenuated to non-significance after adjusted for pre-pregnancy BMI. In the advanced age ( > 30 years) group, STC was significantly associated with risk of GDM in a dose-response manner (P for trend < 0.05). Compared with the Quintile 1, the odds ratios (ORs) (95% confidence interval, CI) of Quintile 2, Quintile 3, Quintile 4, and Quintile 5 were 1.48 (0.62-3.53), 2.70 (1.21-6.03), 2.85 (1.29-6.31), 2.30 (1.05-5.05) in the most adjusted model (including pre-pregnancy BMI). Conclusions: Our study was the first study to demonstrate an association of maternal STC in early pregnancy and risk of GDM, and the association was partly mediated by pre-pregnancy BMI. This association exhibited as an age-dependent manner. Our study highlights even very low-level of thallium exposure could already pose a threat to human's health.