Exposure to several metallic elements has been suggested as a risk factor for gestational diabetes mellitus (GDM), but inconsistent findings have been reported. This study aimed to examine the association between the maternal whole blood concentration of metallic elements (Hg, Pb, Cd, Mn, and Se) and GDM using the dataset of the Japan Environment and Children's Study (JECS), a nationwide birth cohort study, which was designed to examine the adverse effects of pre/post-natal exposure to hazardous environment. The data of 78,964 pregnant women who were participants of JECS were used. Blood samples were collected from the pregnant women at second/third trimester of gestation. We employed logistic regression analysis, quantile g-computation (QGC) and a distributed lag nonlinear model (DLNM) to examine the association between the blood concentration of metallic elements and the risk of GDM. The prevalence of GDM was 2.1%. In the logistic regression analyses, maternal blood Hg was associated with an increased risk of GDM. In QGC analysis, although metallic elements mixtures were not related to an increased risk of GDM, Hg (52.6%) may be the main contributor. According to the results of DLNM, for maternal exposure to Hg, 4.99 ng/g was identified as its susceptible minimum window for elevated risk of GDM. Our findings highlighted an association between Hg exposure and an increased risk of GDM. Studies of the underlying mechanisms and potential contributing factors, including fish intake, of this association are warranted.

Aims: This study investigated the association between maternal age and early and late gestational diabetes mellitus (GDM).Methods: In total, 72,270 pregnant women were included in this prospective birth cohort study. Associations between maternal age and early GDM (diagnosed at <24 gestational weeks) and late GDM (diagnosed at ≥24 gestational weeks) were evaluated using a multinomial logistic regression model with possible confounding factors. The reference category was maternal age of 30–34.9 years.Results: Higher maternal age was associated with higher odds of early and late GDM (P‐value for trend <0.0001 and <0.0001, respectively). The adjusted odds ratios (aORs) for early GDM with maternal age of 35–39.9 years and ≥40 were 1.399 (95% confidence interval [CI]: 1.134–1.725) and 2.494 (95% CI: 1.828–3.402), respectively. The aORs for late GDM with maternal age of 35–39 years and ≥40 were 1.603 (95% CI: 1.384–1.857) and 2.276 (95% CI: 1.798–2.881), respectively.Conclusions: Higher maternal age was associated with an increased risk of GDM regardless of when GDM was diagnosed. The association between maternal age and early GDM was similar to that between maternal age and late GDM.

Objectives: Although a twin pregnancy is a risk factor for hypertensive disorders of pregnancy, studies investigating longitudinal blood pressure changes during twin pregnancies are uncommon. The aims of this study were to evaluate the longitudinal blood pressure changes during twin pregnancies and to compare blood pressure levels between twin and singleton pregnancies. Methods: Five hundred dichorionic diamniotic twin, 240 monochorionic diamniotic twin, and 80 775 singleton pregnancies were included in this Japanese prospective birth cohort study. A marginal model was applied to evaluate the SBP, DBP, and mean arterial pressure levels during early gestation, mid-gestation, and late gestation. Results: The blood pressure levels fell from early-to-mid-gestation and rose after mid-gestation in the dichorionic and monochorionic diamniotic twin pregnancies. The SBP and mean arterial pressure levels during early gestation and the DBP and mean arterial pressure levels during late gestation were higher in the dichorionic diamniotic twin pregnancies than those in the singleton pregnancies. The blood pressure levels in the monochorionic diamniotic twin pregnancies were higher than those in the singleton pregnancies at each gestational stage, except for the SBP during late gestation. Conclusion: Although the longitudinal blood pressure changes during twin pregnancies were similar to those during singleton pregnancies, the blood pressure levels during twin pregnancies were higher. Further studies that examine the associations between the longitudinal blood pressure changes during pregnancy and the perinatal outcomes in twin pregnancies are necessary.