Heavy metals in pregnancy: what lead, arsenic and others can mean for mothers and babies

Lead, arsenic, mercury, manganese and cadmium never break down, and several of them reach a baby before birth. Here is what the evidence shows for each, how strong it is, and how a family can lower the risk from tap water.

Metals such as lead, arsenic, mercury, manganese and cadmium are elements: they never break down. Some of them, lead and cadmium above all, build up in the body over years, in bone and in the kidneys. And a baby can be exposed before birth, because several of them cross the placenta.

That is why these metals matter most for two groups: women who are pregnant or hoping to be, and young children, whose brains are developing fastest and who absorb more of what they swallow. For lead, the US Centers for Disease Control and Prevention (CDC) says no safe level in children has been identified; for lead, and for arsenic, a known cause of cancer, the US Environmental Protection Agency’s health goal in drinking water is zero.

As on our other pages, we say how strong each finding is. Some of these effects are established beyond doubt; others rest on a handful of studies.

Lead

How it gets into water. Almost always from the plumbing, not the source: old lead service pipes, lead solder and brass fittings, mostly in buildings plumbed before the mid-1980s.
In pregnancy. Lead crosses the placenta readily, and a baby’s blood lead closely follows the mother’s. Even fairly low levels in pregnant women have been associated with miscarriage, high blood pressure and pre-eclampsia, premature birth and lower birth weight.
In children. Young children can absorb four to five times as much of the lead they swallow as adults do. Even low levels are linked to developmental delay, learning difficulties, lower IQ and behaviour problems, and the damage does not reverse. This is the best-established harm on this page. More in our article on lead pipes.

Arsenic

How it gets into water. Mostly from natural rock, so it is a question of geology: private wells and boreholes are the usual source, and some regions far more than others. More in our article on arsenic in Greece.
In pregnancy. Recent reviews that pool many studies link higher arsenic exposure to a modestly higher risk of premature birth — about 12 per cent higher odds across 14 studies — and of gestational diabetes.
In children. In Maine, children whose family well water held more arsenic scored lower on IQ tests, including memory and verbal comprehension (2014). A New Hampshire study found early evidence of more infections in babies exposed before birth.

Mercury

How it reaches a baby. Mostly not through tap water, where mercury is rare. The form that harms a developing brain, methylmercury, reaches people mainly through fish, above all large predators such as shark and swordfish.
In pregnancy and childhood. Methylmercury crosses the placenta and can reach higher levels in the baby’s blood than in the mother’s. Exposure in the womb can affect thinking, memory, attention and language, which is why the FDA and EPA advise pregnant women to choose fish low in mercury, not to stop eating fish.

Manganese and cadmium

Manganese is natural in groundwater, especially in wells. In Quebec, children whose tap water was in the highest fifth for manganese scored about six IQ points lower than children with little or none (2011). The EPA advises that babies under six months should not drink water with more than 0.3 mg/L of manganese, or have their formula made with it, for more than ten days a year.
Cadmium comes from corroding galvanised pipes, industry and natural deposits. Over many years above the legal limit it damages the kidneys. In North Carolina, a study of 1.3 million births found an 11 per cent higher chance of premature birth where more than a quarter of wells exceeded the cadmium standard, and more when lead was present too (2023).

At a glance

Metal	Where it comes from	In pregnancy	In children
Lead	Old pipes, solder and brass fittings — the building, not the source	Linked to miscarriage, high blood pressure, premature and smaller babies	No safe level; lower IQ, learning and behaviour problems that do not reverse
Arsenic	Natural rock; wells and boreholes	Linked to premature birth and gestational diabetes	Lower IQ scores; early evidence of more infant infections
Mercury	Mainly fish; rarely tap water	Crosses the placenta; the developing brain is most vulnerable	Problems with thinking, memory, attention and language after exposure in the womb
Manganese	Natural in groundwater, especially wells	Not well studied	Lower IQ scores at high levels
Cadmium	Corroding galvanised pipes, industry	Linked to premature birth, more so together with lead	Mainly a long-term risk: kidney damage after years of exposure

What you can do

Test the water — for arsenic and manganese if it comes from a well or borehole, and for lead in an older building. A national or citywide figure tells you little about your own tap.
Use cold water for drinking, cooking and making formula. Hot water takes up more lead from pipes. If the water has stood in the pipes for hours, run the tap until it turns colder before using it.
Do not boil water to remove metals. Boiling concentrates them.
If a metal is present, treat the water at the tap with something certified for it: a filter certified to NSF/ANSI 53 for lead, or reverse osmosis, which also removes arsenic and cadmium. Replace cartridges on schedule.
Make formula only with water you know is safe, and follow the FDA and EPA advice on choosing fish low in mercury.

Why this matters to us

The Foundation funds water systems for children’s homes and shelters in Greece, and in New York and New Jersey we are building partnerships with organisations that house pregnant women, young mothers and their babies. Nobody living there chose the building or its pipes.

That is why we ask for proof. The Twin system that our partner NearonYdor fits in the homes we fund in Greece was tested by the Chemistry Department of the National and Kapodistrian University of Athens for eight heavy metals. The ordinary tap water used for the test already contained lead at 2.20 micrograms per litre; after filtration, all eight metals were below the limit of detection.

If you would like to help us bring the same water to more mothers and children, the ways to give are on our donate page.

Sources

Centers for Disease Control and Prevention, About childhood lead poisoning prevention (no safe blood lead level in children).
World Health Organization, Lead poisoning, fact sheet.
Agency for Toxic Substances and Disease Registry, Lead toxicity: possible health effects of lead exposure (pregnancy).
US Environmental Protection Agency, National primary drinking water regulations (limits and health goals for lead, arsenic, mercury and cadmium), and Basic information about lead in drinking water.
Maternal exposure to arsenic during pregnancy and risk of preterm birth: a systematic review and meta-analysis (2024).
Maternal arsenic exposure and gestational diabetes: a systematic review and meta-analysis, Nutrients (2020).
Wasserman et al., A cross-sectional study of well water arsenic and child IQ in Maine schoolchildren, Environmental Health (2014).
Farzan et al., In utero arsenic exposure and infant infection in a United States cohort, Environmental Research (2013).
US Environmental Protection Agency, Health effects of exposures to mercury; US Food and Drug Administration, Advice about eating fish.
Bouchard et al., Intellectual impairment in school-age children exposed to manganese from drinking water, Environmental Health Perspectives (2011).
US Environmental Protection Agency, Drinking water health advisory for manganese (2004).
US Environmental Protection Agency, Consumer factsheet on cadmium.
Toxic metal mixtures in private well water and increased risk for preterm birth in North Carolina, Environmental Health (2023).
Laboratory report, Chemistry Department, National and Kapodistrian University of Athens (eight heavy metals).