Maternal and cord blood manganese (Mn) levels and birth weight: The MIREC birth cohort study
- DOI
- Language of the publication
- English
- Date
- 2018-06-07
- Type
- Article
- Author(s)
- Ashley-Martin, Jillian
- Dodds, Linda
- Arbuckle, Tye E.
- Ettinger, Adrienne S.
- Shapiro, Gabriel D.
- Fisher, Mandy
- Monnier, Patricia
- Morisset, Anne-Sophie
- Fraser, William D.
- Bouchard, Maryse F.
- Publisher
- Elsevier
Abstract
Epidemiological studies have hypothesized that both insufficient and excess blood manganese (Mn) levels during pregnancy are associated with reduced fetal growth. This literature is characterized by inconsistent results and a limited focus on women with exposures representative of the general North American population. We examined the relationship between maternal and cord blood Mn levels and fetal growth among women enrolled in the Maternal-Infant Research on Environmental Chemicals Study (MIREC). Mothers with singleton, term infants and complete maternal first and third trimester blood Mn data were eligible for inclusion in the present study (n = 1519). Mean birth weight and odds ratios of small for gestational age (SGA) births according to maternal and cord blood Mn levels (low (<10), referent (10–<90), high (≥90) percentiles) were estimated. We also evaluated the association between the ratio of cord and maternal blood Mn and birth weight. Women with low (<0.82 μg/dL) maternal blood third trimester Mn levels had infants that weighed an average of 64.7 g (95% CI: −142.3,12.8) less than infants born to women in the referent exposure group. This association was strengthened and became statistically significant when adjusted for toxic metals (lead, mercury, arsenic, and cadmium) [−83.3 g (95% CI: −162.4, −4.1)]. No statistically significant associations were observed in models of maternal first trimester or cord blood Mn. A one unit increase in the cord/maternal blood Mn ratio was associated with a 29.4 g (95% CI: −50.2, −8.7), when adjusted for maternal and neonatal characteristics. Our findings motivate additional research regarding the relation between Mn exposure and fetal growth. Further inquiry is necessary to determine whether an exposure threshold exists, how growth related effects of maternal and fetal Mn may differ, and how concurrent exposure to other toxic metals may impact the association between Mn and growth.
Plain language summary
"Health Canada helps to protect the health of Canadians by assessing and managing the health risks associated with exposure to environmental contaminants. Manganese is an essential nutrient for human health, especially in pregnancy. Some studies have suggested that either low or high levels of manganese in maternal blood during pregnancy are associated with lower birth weight; however, it is not known whether these associations occur at the levels experienced by Canadian women. To answer this question, researchers from Dalhousie University led an analysis of data from the Maternal-Infant Research on Environmental Chemicals (MIREC) Study. Maternal blood from the 1st and 3rd trimesters of pregnancy in about 1,500 women, as well as umbilical cord blood, were analysed for manganese. Information on the birth weight and gestational age at delivery for singleton term infants was available from the questionnaires and medical charts of women in the study. Manganese levels tend to increase through pregnancy and be even higher in cord blood. The average maternal blood manganese level in the 1st trimester for MIREC participants was 9 µg/L and increased to 13 µg/L in the 3rd trimester and was 32 µg/L in cord blood. Women with lower blood manganese levels (< 6 µg/L) in the 1st trimester tended to have infants with lower birth weight (average difference 22 g (95% CI: -98, +53 g)). Women with higher 1st trimester blood manganese (≥ 13.2 µg/L) also tended to have infants with lower birth weight. In addition, the odds ratio of having a baby that was small for its gestational age and sex was 1.8 (95% CI: 0.8, 3.9) if the cord blood level was > 48.4 µg/L. However, none of these results were statistically significant. In this group of Canadian women, neither maternal nor cord blood manganese were significantly associated with lower birth weight"
Subject
- Health,
- Health and safety