Heavy metal levels in human placentas

Introduction: Particulate matter (PM) had been associated with adverse
pregnancy outcomes potentially by increasing exposure to PM-linked
heavy metals.
Objectives: To investigate heavy metal exposure in pregnant women, we
determined levels of heavy metal in placental samples and examined their
association with ambient air pollution and birth weight.
Methodology: 30 placentas were sampled following elective delivery
between March and May 2016 at St. Mary’s Hospital, Manchester. Placentas
were analysed for 15 different metals and associations with SGA
(defined as 20th percentile) examined. Associations with ambient air
pollutions obtained from ArcGIS were also measured.
Results: All placentas contained detectable levels of physiological metals
K, P, Cu, Mg, Na, Se and Zn ( 2 fold interindividual variation) and Ca, Cd
and Fe (variation higher at 14.6, 12 and 4.4 fold, respectively). Pollutant
metals As, Cr, Hg, Ni and Pb were also detected at maximum levels of 0.003,
0.4, 0.006, 0.05 and 0.006 mg/kg, respectively. Placentas from SGA baby
births were significantly less likely to contain Ni, being absent in all 8 SGA
samples whilst being absent in only 11 out of 22 normal placentas (p ¼
0.01). There were no other associations between heavy metals and SGA or
between heavy metal levels and ambient air pollutants (NOx and PM10).
Conclusion: This pilot study had identified a potential association between
heavy metal levels during pregnancy and SGA, but larger numbers
of samples are required to confirm this.