Prenatal exposure to chromium may be associated with reduced birth weight; however, critical windows of such exposure for fetal growth are unclear. Our study was aimed to assess trimester-specific associations of chromium exposure with fetal growth parameters measured repeatedly by ultrasound and birth size, and to see whether these associations were modified by fetal sex. We conducted a prospective cohort of 3041 women in Wuhan, China, from 2013 to 2016. Chromium concentrations were measured in maternal urine samples collected in the 1st, 2nd, and 3rd trimesters using an inductively coupled plasma mass spectrometry. We calculated standard deviation scores for ultrasound measured head circumference, abdominal circumference (AC), femur length, and estimated fetal weight (EFW) at 16, 24, and 31 weeks of gestation. Linear regressions with generalized estimating equations were used to estimate the associations of specific gravity-adjusted urinary chromium concentrations in each trimester with fetal growth parameters and birth weight, birth length, and ponderal index. Inverse associations of chromium exposure in the 1st trimester with fetal growth parameters at 31 weeks of gestation were observed, resulting in significant reductions in AC of -5.4% (95% confidence interval [CI]: -9.6%, -1.2%) and EFW of -5.6% (95% CI: -9.8%, -1.4%) per unit increase in natural logarithm transformed urinary chromium concentration. Urinary chromium concentration in the 2nd trimester was also associated with reductions in AC of -7.0% (95% CI: -12.5%, -1.4%) and in EFW of -5.0% (95% CI: -10.6%, 0.6%) at 31 weeks, and these inverse associations were evident in boys (reduction in AC of -13.9% [95% CI: -21.1%, -6.7%]; EFW of -9.5% [95% CI: -16.9%, -2.0%]) but not in girls (increase in AC of 2.9% [95% CI: -5.7%, 11.5%]; EFW of 1.5% [95% CI: -6.8%, 9.8%]) (both pineraction < 0.05). Moreover, one-unit increase in urinary chromium concentrations in the 1st and 2nd trimesters were both associated with significant reductions in ponderal index of -0.11 kg/m3 (95% CI: -0.19, -0.03 kg/m3) and -0.15 kg/m3 (95% CI: -0.27, -0.03 kg/m3), respectively. Our findings suggest that chromium may be a toxic metal for fetal growth. Early and mid-pregnancy seem to be the most vulnerable period for fetal exposure to chromium, but these results need further confirmation.

The existing studies on the association between multi-metal mixture exposure and cognitive function in the older adults are limited and controversial, with no studies considering the mediating effect of thyroid hormones on the connection between them. This study of 441 urban older adults assessed 21 urinary metal levels and cognitive function using the Mini-Mental State Examination (MMSE). Urinary metal levels were measured via inductively coupled plasma mass spectrometry (ICP-MS), and thyroid hormones levels were obtained from medical records. Mediation analysis evaluated the role of thyroid hormones in the link between metals exposure and cognitive function. The General Linear Model (GLM) showed negative correlations between MMSE scores and titanium (Ti), copper (Cu), rubidium (Rb), and molybdenum (Mo), and positive correlations with selenium (Se) and barium (Ba). Nonlinear inverse U-shaped associations between Mo, Rb, and MMSE scores were identified using Restricted Cubic Splines (RCS) and Bayesian Kernel Machine Regression (BKMR). Mediation analysis revealed that Free Thyroxine (FT4) mediated the relationship between Rb and MMSE scores by 29.10 % and between Zinc (Zn) and language performance by 35.00 %. Total thyroxine (TT4) mediated the link between Cu and orientation score by 24.69 %, and Thyroid Stimulating Hormone (TSH) mediated the association between Cu and attention score by 38.96 %. Ti, Se, Rb, Mo, Ba and Cu were significantly associated with cognitive impairment risk. Mixed exposure to Mo and Rb was linked to an increased risk of cognitive impairment. Additionally, levels of TSH, FT4 and TT4 were associated with cognitive function, mediating the effects of Rb, Zn and Cu on cognitive function.

Summary Risk factors for adverse pregnancy outcomes among Zhuang ethnic pregnant women are unclear. This study analyzed the incidence and risk factors related to preterm birth (PB), low birth weight (LBW) and macrosomia in Zhuang population. We conducted a prospective cohort study of 9965 Zhuang pregnancy women in Guangxi, China. Information on mothers and newborns was obtained by using questionnaires and referring to medical records. Multivariate logistic regression analyses were used to evaluate the association between related factors and adverse pregnancy outcomes. Our results showed that the incidence of PB, LBW and macrosomia in Zhuang people was 5.55%, 5.64% and 2.19%, respectively. Maternal age ≥36 years (OR=2.22, 95% CI: 1.51–3.27) was related to a higher incidence of PB. Those with pre-pregnancy body mass index (BMI) <18.5 kg/m² (OR=1.91, 95% CI: 1.45–2.51), and had a female fetus (OR=1.74, 95% CI: 1.36–2.23) were more likely to have LBW infants. Maternal age between 31 and 35 years (OR=1.76, 95% CI: 1.03–2.99) and pre-pregnancy overweight or obesity (OR=1.79, 95% CI: 1.15–2.80) were associated with a higher risk of macrosomia. The protective factors of macrosomia were maternal pre-pregnancy BMI <18.5 kg/m² (OR=0.30, 95% CI: 0.15–0.60) and female fetus (OR=0.41, 95% CI: 0.28–0.59). Our study provided a reference for maternal and childcare administration among Zhuang population.