Can heavy metal exposure during pregnancy affect your baby's brain development?

What's actually in it

A pregnant person absorbs lead, mercury, cadmium, arsenic, and manganese from food, water, and household products daily. These metals reach the baby through the placenta, but the placenta doesn't treat all metals equally. Some pass through freely, while others are partially blocked or even concentrated.

How much of each metal the baby actually receives depends on the placental transfer efficiency, the ratio of metal in cord blood versus maternal blood.

What the research says

A 2026 study in Environ Int measured metal levels in both maternal blood and umbilical cord blood, calculated the placental transfer ratio for each metal, and assessed neonatal neurodevelopment using standard tests at birth.

Mercury showed the highest transfer efficiency, with cord blood levels often exceeding maternal levels. Babies with higher mercury transfer had lower neurological optimality scores, a composite measure of reflexes, muscle tone, and behavioral responses.

Lead transferred at near 1:1 ratio. Even small differences in placental lead transfer predicted differences in motor development scores. Manganese showed a U-shaped pattern: both too little and too much were associated with worse outcomes, since manganese is an essential nutrient at low levels but neurotoxic at high levels.

The placenta provides some protection against cadmium, which transferred less efficiently. But it offered almost no barrier against mercury and lead.

Reducing metal intake during pregnancy matters most for mercury (limit high-mercury fish) and lead (filter water, manage paint dust in older homes). These are the metals the placenta does the least to block.