Psychosocial status modifies the effect of maternal blood metal and metalloid concentrations on birth outcomes

Abstract

Background: Metal exposure and psychosocial stress in pregnancy have each been associated with adverse birth outcomes, including preterm birth and low birth weight, but no study has examined the potential interaction between them.

Objectives: We examined the modifying effect of psychosocial stress on the association between metals and birth outcomes among pregnant women in Puerto Rico Testsite for Exploring Contamination Threats (PROTECT) birth cohort study.

Methods: In our analysis of 682 women from the PROTECT study, we measured 16 essential and non-essential metals in blood samples at two time points. We administered questionnaires to collect information on depression, perceived stress, social support, and life experience during pregnancy. Using K-means clustering, we categorized pregnant women into one of two groups: "good" and "poor" psychosocial status. We then evaluated whether the effect of blood metals (geometric average) on adverse birth outcomes (gestational age, preterm birth [overall and spontaneous], birth weight z-score, small for gestation [SGA], large for gestation [LGA]) vary between two clusters of women, adjusting for maternal age, maternal education, pre-pregnancy body mass index (BMI), and second-hand smoke exposure.

Results: Blood manganese (Mn) was associated with an increased odds ratio (OR) of overall preterm birth (OR/interquartile range [IQR] = 2.76, 95% confidence interval [CI] = 1.25, 6.12) and spontaneous preterm birth (OR/IQR: 3.68, 95% CI: 1.20, 6.57) only among women with "poor" psychosocial status. The association between copper (Cu) and SGA was also statistically significant only among women having "poor" psychosocial status (OR/IQR: 2.81, 95% CI: 1.20, 6.57). We also observed associations between nickel (Ni) and preterm birth and SGA that were modified by psychosocial status during pregnancy.

Conclusions: Presence of "poor" psychosocial status intensified the adverse associations between Mn and preterm birth, Cu and SGA, and protective effects of Ni on preterm. This provides evidence that prenatal psychosocial stress may modify vulnerability to metal exposure.

Keywords: Manganese; Metals; Prenatal stress; Puerto Rico; Social support.

Figure 1.

PROTECT cohort study design and sample size

Figure 2.

Cluster means of the four standardized psychosocial variable scales using k-means in the PROTECT data^ab. Abbreviations: Center for Epidemiological Studies-Depression (CESD); Perceived Stress Scale (PSS); Enhancing Recovery in Coronary Heart Disease Patients (ENRICHD) Social Support Instrument (ESSI); Life Experience Survey (LES). ^a Y-axis (cluster means) represents the mean standardized psychosocial variable scale. ^b Cluster 1: “good” overall psychosocial status pattern with low depression score and perceived stress and high social support and overall positive life events; cluster 2: “poor” overall psychosocial status pattern with high depression score and perceived stress and low social support and overall negative life events;

Figure 3.

Change in birth outcomes associated with geometric mean exposure biomarker concentration within two psychosocial status clusters. Effect estimates presented as changes in gestation or odds ratio (OR) for IQR increase in exposure biomarker concentration^a. Models were adjusted for maternal age, maternal education, pre-pregnancy BMI, and exposure to secondhand smoking. Abbreviations: cobalt (Co); cesium (Cs); copper (Cu); manganese (Mn); nickel (Ni); zinc (Zn); arsenic (As); cadmium (Cd); mercury (Hg); lead (Pb). ^aAs, Cd were compared between two categories of above LOD and below LOD. *indicates p for interaction <0.1 considered significant for interaction metal*psychosocial status, ** indicates p for interaction <0.1 & q for interaction <0.1