The relationship between urinary selenium levels and risk of gestational diabetes mellitus: A nested case-control study.

Background: Selenium (Se) is an essential trace element for the human body. Serum Se and urinary Se are also biomarkers to assess Se exposure status. However, studies focusing on the association between urinary Se and the risk of gestational diabetes mellitus (GDM) are rare. Objective: To investigate the association between urinary Se and the risk of GDM. Methods: A nested case-control study based on a prospective birth cohort in Wuhan, China, which focuses on the effects of prenatal environmental factors exposure on pregnant women and children's health was conducted. Two hundred and twenty-six cases and 452 controls were included. Maternal urine samples were collected before GDM diagnosis, and the urinary Se levels were determined. We assessed the association of urinary Se with GDM by conditional logistic regression with maternal urinary Se level as a categorical variable, and estimated the association between Se and glucose levels by multiple linear regression. The potential modifier roles of maternal age and fetal sex have also been assessed. Results: Lower urinary level of Se was significantly associated with a higher risk of GDM (OR = 2.35 for the tertile 1, 95% CI:1.36-4.06; adjusted OR = 1.79 for the tertile 2, 95%CI:1.09-2.95; p for trend = 0.01). Fetal sex had an interaction with Se in the association with GDM. The association was more pronounced among pregnant women with female fetuses than with male fetuses. Discussion: Our study suggested a significant negative association between urinary Se and the risk of GDM, and this association may vary depending on the fetal sex.

The dynamic change of urinary selenium concentration during pregnancy and influencing factors: A longitudinal study.

BACKGROUND: Selenium concentration of one spot urine sample cannot reflect selenium status during whole pregnancy. Studies on variations of urinary selenium concentration at different stages of pregnancy are limited. AIM: To assess variations of urinary selenium concentrations during three trimesters of pregnancy and to explore the influencing factors. METHODS: This study included 2613 pregnant women from a birth cohort study (Wuhan, China) enrolled between October 2014 and October 2016. Selenium concentrations of urine samples collected at three trimesters were measured. We used a generalized linear mixed effects model to observe the changes in urinary selenium concentration during pregnancy and its influencing factors. RESULTS: The median value (range) of gestational weeks at urine sample collection was 11 (9-14), 24 (15-27), and 34 (28-41) respectively. Urine selenium concentration varied across trimesters (geometric mean: 16.34, 17.65 and 18.83 µg/g creatinine, respectively), with an upward trend (ß = -0.145, 95%CI: -0.164, -0.126) (ß = -0.066, 95%CI: -0.083, -0.048). The concentrations of urinary selenium increased with the increasing of educational level [ß (95%CI): ≤ 9 years = -0.105 (-0.163, -0.047); 10-12 years = -0.086(-0.126, -0.047); > 12 years = reference]. Pregnant women who rarely or only took multivitamins in the first trimester [ß (95% CI): rarely = -0.076 (-0.144, -0.007); only in the first three months of pregnancy = -0.104 (-0.170, -0.038); always = reference], or were not exposed to passive smoking during pregnancy（ߠ= -0.093, 95% CI: - 0.173, - 0.014), or exercised three to four days per week for the first three months before delivery（ߠ= -0.074, 95% CI: - 0.140, - 0.008) had lower urinary selenium concentrations. Pregnant women who took calcium supplements after the third month of pregnancy had higher urinary selenium levels（ߠ= 0.114, 95% CI: 0.059, 0.169). CONCLUSIONS: Urine selenium concentrations of pregnant women showed an upward trend across trimesters. Educational level, calcium or multivitamin supplementation, passive smoking, and physical exercise might impact urine selenium levels.