Early pregnancy blood heavy metal(loid)s and low sea-fish consumption in relation to risk of gestational diabetes mellitus among Shanghai Birth cohort (SBC) women

BACKGROUND: Gestational diabetes mellitus (GDM) is a common metabolic complication during pregnancy which increase both maternal and fetal adverse outcomes. Selected heavy metal(loid)s may lead to insulin resistance and increase risk of GDM. We sought to investigate associations between maternal heavy metal(loid)s exposure, sea-fish consumption and GDM risk. METHODS: In 2174 women, including 686 with GDM, 48 with preexisting diabetes mellitus (PDM), and 1440 euglycemic pregnancies from the Shanghai Birth Cohort, we measured maternal whole blood concentrations of 13 metal(loid)s including mercury (Hg), arsenic, cadmium, lead, magnesium, calcium, manganese, iron, copper, zinc, selenium, rubidium, and strontium at early pregnancy. Logistic regressions were used to evaluate the associations of prenatal blood metal(loid)s with GDM and PDM, and linear regressions for plasma glucose (fasting, 1-hour, and 2-hour) during 75 g-oral glucose tolerance test (OGTT), with stratification by prenatal fish consumption and adjusting for pertinent covariates. RESULTS: Early pregnancy blood Hg concentrations were higher in women with GDM and PDM versus euglycemic (geometric mean was 1.88, and 2.18 versus 1.74 μg/L). Compared with the lowest quintile of Hg, the highest Hg quintile was associated with 1.66-fold higher odds of GDM (95 % CI: 1.17, 2.37, P < 0.01) and 7.10-fold higher odds (95 % CI: 1.82, 47.06, P < 0.05) of PDM. Consistently, blood Hg was also positively associated with higher plasma glucose at fasting, 1-hour, and 2-hour during OGTT. No significant associations were found between other measured metal(loid)s and GDM or PDM. The positive Hg-associations with GDM, PDM， and plasma glucoses were stronger among women with low fish intake (<1 time/week) and not statistically significant among higher sea-fish intake (interaction test P < 0.05). CONCLUSIONS: In this prospective birth cohort, despite relatively low maternal Hg exposure, maternal Hg during early pregnancy was positively associated with increased risk of GDM and PDM, while higher sea-fish consumption showed counteracting effect.