Mercury Amalgam Fillings During Pregnancy: Is It Safe?

What does the evidence say about mercury amalgam fillings during pregnancy?

1. FDA identifies pregnant women and women planning pregnancy as a high-risk group because placement of new amalgam fillings in a pregnant mother may result in high, transient spikes of mercury exposure to the mother and fetus, and recommends avoiding dental amalgam if possible and appropriate when a new filling is needed. 1
2. Existing intact fillings are a separate question from new ones: FDA states that intact amalgam fillings, including in pregnant or nursing mothers, should not be removed for the purpose of reducing the chance of any disease or health condition unless considered medically necessary by a health care professional. 1
3. Dental amalgam is roughly half elemental mercury by weight, mixed with a powdered alloy of silver, tin, and copper, and while FDA states this exposure does not lead to negative health effects in the general population, it strongly encourages non-amalgam restorations for high-risk groups, including pregnant women, when appropriate alternatives exist. 2
4. Research offers some reassurance about the level of exposure involved: a prospective study of 72 pregnant women found that more and larger amalgam fillings modestly raised mercury concentration in amniotic fluid, but levels detected were low and no adverse outcomes were observed during the pregnancy or in the newborns. 3
5. In a larger study comparing 1,117 women who had low-birth-weight infants with 4,468 women who did not, the 4.9% of women who had at least one amalgam filling placed during pregnancy were not found to be at greater risk for a low-birth-weight infant, and cord blood mercury levels in the reviewed research stayed below the level considered hazardous for neurodevelopmental effects. 3
6. Dental amalgam is a source of elemental mercury specifically, a different form from the methylmercury found in certain fish that pregnancy guidance separately warns about, though MedlinePlus notes the nervous system is sensitive to all forms of mercury and that pregnant women can pass mercury in their bodies to their babies. 4

Is mercury amalgam fillings safe in each trimester?

• First trimester. If a cavity is found early in pregnancy, ask your dentist about non-amalgam filling materials before agreeing to a specific option, since this is the recommended approach whenever a reasonable alternative exists for a pregnant patient.
• Second trimester. Routine dental care, including checkups and cleanings, is still appropriate in the second trimester. If a filling becomes necessary, this is a good window for non-urgent dental work, approached with the same amalgam-avoidance-when-possible thinking as any other trimester.
• Third trimester. Untreated dental disease does not become less important late in pregnancy, so a genuinely necessary filling should not be delayed on mercury-exposure grounds alone. The guidance is about material choice when there is a choice, not about avoiding needed dental care altogether.