Maternal urinary manganese and risk of low birth weight: a case–control study

Abstract

BackgroundManganese (Mn) is an essential element for humans, but exposure to high levels has been associated with adverse developmental outcomes. Early epidemiological studies evaluating the effect of Mn on fetal growth are inconsistent.MethodsWe investigated the association between maternal urinary Mn during pregnancy and the risk of low birth weight (LBW). Mn concentrations in maternal urine samples collected before delivery were measured in 816 subjects (204 LBW cases and 612 matched controls) recruited between 2012 and 2014 in Hubei Province, China.ResultsThe median Mn concentration in maternal urine was 0.69 μg/g creatinine. Compared to the medium tertile of Mn levels, an increased risk of LBW was observed for the lowest tertile (≤0.30 μg/g creatinine) [adjusted odds ratio (OR) = 1.28; 95 % confidence interval (CI) = 0.67, 2.45], and a significantly increased risk of LBW was observed for the highest tertile (≥1.16 μg/g creatinine) [adjusted OR = 2.04; 95 % CI = 1.12, 3.72]. A curvilinear relationship between maternal urinary Mn and risk of LBW was observed, showing that the concentration at 0.43 μg/g creatinine was the point of inflection. Similar associations were observed among the mothers with female infants and among the younger mothers < 28 years old. However, among the mothers with male infants or the older mothers ≥ 28 years old, only higher levels of Mn were positively associated with LBW.ConclusionsLower or higher levels of maternal urinary Mn are associated with LBW, though only the association of LBW risk and higher levels of Mn was statistically significant. The findings also show that the associations may vary by maternal age and infant sex, but require confirmation in other populations.Electronic supplementary materialThe online version of this article (doi:10.1186/s12889-016-2816-4) contains supplementary material, which is available to authorized users.

Critical Windows for Associations between Manganese Exposure during Pregnancy and Size at Birth: A Longitudinal Cohort Study in Wuhan, China

“…2009). However, urinary Mn concentrations of the study population were higher than that of the subpopulation in our previous study (Xia et al. 2016), of pregnant women from an agricultural community in California (Gunier et al.…”

“…2015). In addition, one of our previous studies suggested that exposure to higher levels of Mn, even at levels that did not exceed the upper limit of urinary reference (10μg/L) (McClatchey 2002), was associated with an increased risk of low birth weight (Xia et al. 2016).…”

In utero metal exposures measured in deciduous teeth and birth outcomes in a racially-diverse urban cohort

“…In a study in Hubei Province, China, maternal pre-delivery urine manganese levels demonstrated a curvilinear association with low birth weight in female infants but a linear association in male infants. 30 Additional work to confirm our findings is needed.…”

“…32 Similar findings were obtained in a case-control study conducted in Hubei Province, China, which showed both lower and higher maternal urinary manganese measured at delivery was associated with low birth weight. 30 In contrast, in a study in Taiwan, first and second, but not third trimester maternal erythrocyte manganese levels were inversely associated with infant birth weight. 33 We found that tooth manganese levels in the second and third trimester were positively associated with birth weight, even after adjustment for covariates.…”

“…Manganese is an essential nutrient and as such, is necessary for proper growth and development, however, manganese at higher levels can also be toxic. 30,31 Similar to lead, there is a growing body of literature showing the importance of manganese in healthy birth outcomes. Data from 172 mother-infant-pairs born in Shanghai showed both lower and higher maternal manganese levels in blood measured near delivery were associated with lower birth weight.…”