Maternal urinary cadmium concentrations in relation to preterm birth in the Healthy Baby Cohort Study in China.

Background: Prenatal cadmium (Cd) exposure has been associated with adverse birth outcomes, but the findings of previous studies are inconsistent. The aim of this study was to evaluate the association between prenatal Cd exposure and birth outcomes.

Methods: This study was conducted in 5364 pregnant women with a live singleton birth, who were recruited between September 2012 and October 2014 in the Healthy Baby Cohort (HBC) in Wuhan, China. Gestational age (in days) was estimated using both the woman's last menstrual period (LMP) and ultrasound data. All the birth outcomes including birth weight and birth length were measured in the hospital within one hour after birth through standardized procedures. Cd was measured in maternal urine collected before delivery with inductively coupled plasma mass spectrometry.

Results: The geometric mean of Cd concentration in maternal urine was 0.55 (range 0.01-2.85) μg/g creatinine. We found each ln-unit increase in Cd concentration (μg/g creatinine) in maternal urine was associated with decreased gestational age [adjusted β=-0.77day; 95% confidence interval (CI): -1.15, -0.39 for all infants; -0.77; 95% CI: -1.29, -0.25 for boys; and -0.80; 95% CI: -1.35, -0.25 for girls]. Increased likelihood of preterm birth (PTB) was associated with ln-unit increase in urinary Cd (μg/g creatinine) [adjusted odds ratio (OR)=1.78; 95% CI: 1.45, 2.19 for all infants; 1.97; 95% CI: 1.46, 2.65 for boys; and 1.67; 95% CI: 1.24, 2.25 for girls]. Maternal urinary Cd was not significantly associated with low birth weight (LBW) and small for gestational age (SGA).

Conclusions: Maternal exposure to Cd during pregnancy was associated with decreased gestational age and increased likelihood of PTB.