Impact of organic mercury exposure and home delivery on neurodevelopment of Amazonian children

- Home birth is associated with decreased EtHg and increased MeHg exposures.
- Neurodevelopment was not associated with birth (home vs hospital) environment.
- Neurocognitive tests used were not sensitive to levels of MeHg and EtHg exposure.

In the transitioning Amazon, we addressed birth environment (home vs hospital) and associated perinatal organic-Hg exposures: methylmercury (MeHg) from maternal fish consumption and ethylmercury (EtHg) from pediatric Thimerosal-containing vaccines (TCVs) taken systematically during hospital delivery. We studied 365 children in relation to linear growth at 60 months and neurodevelopment (milestone achievements, Bayley Scale of Infant Development/BSID at 24 months, and Stanford-Binet intelligence tests at 60 months). Mothers delivered in hospitals vs those gave birth at home had significantly (p < 0.0001) lower hair-Hg (HHg) concentrations (12.2 vs 23.9 μg/g respectively) and shorter length of breastfeeding (8.5 vs 9.7 months respectively). Home-born children had significantly (p < 0.0001) higher HHg (7.1 μg/g) than hospital-born children (4.6 μg/g). Hospital-born children also had significantly earlier (p < 0.0001) hepatitis B vaccine than home-born children (1.5 vs 24.1 days respectively) and higher (p < 0.0001) exposures to total TCV-EtHg (75.8 vs 49.3 μg respectively). Neither anthropometric indices nor neurodevelopment (except for fluid reasoning) were directly affected by birth environment. The percentage of hospital-born children with BSID (MDI or PDI) scores <80 was not significantly different from those born at home. In spite of the differences in HHg and EtHg levels between hospital-born and home-born children, no impact on neurodevelopment was observed.