Amalgam Removal During Pregnancy: Why It Must Wait

Pregnancy, Breastfeeding, and Mercury Removal: What Must Not Be Done

Biological dentistry exists because a small number of very smart people were willing to acknowledge and push for the truth on something conventional dentistry ignored for decades: dental materials are not biologically inert.  Mercury is the worst of them, though fluoride and BPA make the trifecta of toxicity within our profession.  

That said, biological dentistry also requires restraint — and nowhere is that more important than during pregnancy and breastfeeding.  Mercury amalgam removal must NEVER be performed during pregnancy or lactation.  This is not a matter of philosophy or technique.
It is a matter of toxicology, placental physiology, and infant neurodevelopment.

Mercury Exposure Increases During Amalgam Removal

Dental amalgam is approximately 50% elemental mercury by weight. When amalgams are drilled or removed, mercury vapor is released and absorbed rapidly through the lungs and  into systemic circulation.  

1. Sandborgh-Englund G, Elinder CG, Langworth S, Schütz A, Ekstrand J .  PMID: 9539465

https://pubmed.ncbi.nlm.nih.gov/9539465

After removing all amalgam fillings in one session, mercury levels in blood and plasma temporarily increased by an average of 32% within 48 hours, then declined over the following months.

2. Berglund A, Molin M .  PMID: 9823089

https://pubmed.ncbi.nlm.nih.gov/9823089

Patients who had amalgam removed without a rubber dam showed significant increases in blood mercury levels the day after removal, while those protected by a rubber dam did not show significant increases.

3. Halbach S, Welzl G, Kremers L, et al.   PMID: 11032131

https://pubmed.ncbi.nlm.nih.gov/11032131

Mercury levels in blood plasma peaked at an average of 0.6 nanograms per milliliter one day after amalgam removal in patients protected by rubber dams, then decreased over the following months.

4. Halbach S, Vogt S, Köhler W, et al.    PMID: 17767927

https://pubmed.ncbi.nlm.nih.gov/17767927

After amalgam removal, inorganic mercury dropped rapidly in plasma and red blood cells, stabilizing at 27% of pre-removal levels after 60 days in a randomized controlled trial of 82 patients.

The key finding across these studies is that the acute rise in mercury is transient and small in magnitude—typically peaking within 24-48 hours and then declining below baseline levels over subsequent weeks to months. The use of rubber dams during removal significantly reduces or eliminates the acute spike in blood mercury.  Urine mercury levels generally do not show an acute increase after removal, but instead decline progressively over time.  Given the fact that there is NO safe level of mercury, even a temporary spike would be detrimental to a developing fetus or a breastfeeding baby.  This is NOT what we wish to do to our babies.  Even though the levels decline sharply after about 3 days, there is still SOME increase in mercury blood levels even when the process is done with a rubber dam.  This is why SMART/PROTECT exists.  

Though SMART/PROTECT protocols significantly reduce exposure — they do not eliminate it.

That distinction matters enormously during pregnancy.

Mercury Crosses the Placenta — Easily

The placenta is not a protective barrier against mercury. It is an exchange interface.

Mercury crosses the placenta via neutral amino acid transporters, allowing fetal exposure even when maternal levels appear modest. Studies demonstrate that fetal mercury concentrations can equal or exceed maternal blood levels.

1. Straka E, Ellinger I, Balthasar C, et al.   PMID: 26740192

https://pubmed.ncbi.nlm.nih.gov/26740192

Methylmercury crosses the placenta using amino acid transporters (LAT1 and rBAT) on the mother-facing side that mistake mercury-cysteine complexes for the amino acid methionine, explaining why mercury efficiently reaches the fetus.

2. Balthasar C, Stangl H, Widhalm R, et al.     PMID: 28786956

https://pubmed.ncbi.nlm.nih.gov/28786956

The amino acid transporter LAT2-4F2hc carries methylmercury-cysteine complexes into placental cells because they look similar to methionine, which is why mercury crosses the placenta more efficiently than other heavy metals like lead or cadmium.

3. Sakamoto M, Chan HM, Domingo JL, Koriyama C, Murata K.    PMID: 29150340

https://pubmed.ncbi.nlm.nih.gov/29150340

Cord blood mercury levels (7.26 ng/g) were 1.9 times higher than maternal blood levels (3.79 ng/g), while protective nutrients like vitamin E and DHA were much lower in cord blood, suggesting fetuses face higher mercury toxicity risk.

4. Ou L, Chen L, Chen C, et al.     PMID: 24792881

https://pubmed.ncbi.nlm.nih.gov/24792881

A meta-analysis of multiple studies found that fetuses are exposed to approximately twice as much methylmercury as their mothers (cord-to-maternal blood ratio of 1.89), while inorganic mercury levels are similar between mother and fetus.

5. Sakamoto M, Haraguchi K, Tatsuta N, et al.     PMID: 33640495

https://pubmed.ncbi.nlm.nih.gov/33640495

Cord blood had 1.58 times more mercury than maternal blood, showing that methylmercury actively transfers from mother to fetus through the placenta, with cord blood being particularly rich in the organic form that easily enters the developing brain.

6. Zhang T, Wang X, Luo ZC, et al.    PMID: 37625333

https://pubmed.ncbi.nlm.nih.gov/37625333

The placental transfer ratio for mercury was 1.68, meaning fetuses had 68% more mercury than their mothers, demonstrating a high degree of transplacental passage that poses hazards to the developing fetus.

These articles collectively demonstrate that the PLACENTA ACTIVELY CONCENTRATES mercury in fetal circulation rather than protecting against it, that L-type amino acid transporters (LAT1, LAT2) mediate uptake by mistaking methylmercury-cysteine for methionine, and that fetal mercury levels consistently exceed maternal levels by 1.5-2 fold across multiple populations and study designs.

Once across the placenta:

• Mercury accumulates in fetal brain tissue

• The developing nervous system lacks detoxification capacity

• Damage occurs at exposure levels tolerated by adults

This is why prenatal mercury exposure has been linked to measurable cognitive, motor, and neurologic deficits later in childhood.

1. Grandjean P, Landrigan PJ .  PMID: 17174709

https://pubmed.ncbi.nlm.nih.gov/17174709

Studies in New Zealand found a three-point IQ drop in children whose mothers had hair mercury above 6 micrograms per gram, while Faroe Islands studies showed memory, attention, language, and visual-spatial problems related to mercury dose.

2. Axelrad DA, Bellinger DC, Ryan LM, Woodruff TJ .    PMID: 17450232

https://pubmed.ncbi.nlm.nih.gov/17450232

Combining data from three major studies, researchers found that for every 1 part per million increase in maternal hair mercury, children's IQ dropped by 0.18 points on average.

3. Kim Y, Ha EH, Park H, et al.   PMID: 29751424

https://pubmed.ncbi.nlm.nih.gov/29751424

Higher mercury levels in early pregnancy were linked to lower mental and motor development scores at 6 months of age, even after accounting for beneficial nutrients from fish.

4. Lam HS, Kwok KM, Chan PH, et al.    PMID: 23416249

https://pubmed.ncbi.nlm.nih.gov/23416249

Hong Kong children with higher prenatal mercury exposure performed worse on visual sequencing tasks and verbal memory retention tests at age 8, showing long-term effects even at low exposure levels.

5. Freire C, Amaya E, Gil F, et al.    PMID: 29190557

https://pubmed.ncbi.nlm.nih.gov/29190557

Children with detectable arsenic in their placentas had lower verbal and math scores, while those with higher mercury had worse verbal and motor skills at ages 4-5 years.

6. Cardenas A, Rifas-Shiman SL, Agha G, et al.   PMID: 28325913

https://pubmed.ncbi.nlm.nih.gov/28325913

Prenatal mercury exposure caused lasting DNA methylation changes in the PON1 gene that persisted into early childhood and were associated with lower cognitive test scores in young children.

7. Kim B, Shah S, Park HS, et al.    PMID: 32871452

https://pubmed.ncbi.nlm.nih.gov/32871452

Mercury's harmful effects on brain development were worse in children who grew rapidly during their first 3 years and whose mothers had low folate levels during pregnancy.

8. Saavedra S, Fernández-Recamales Á, Sayago A, et al.    PMID: 33954792

https://pubmed.ncbi.nlm.nih.gov/33954792

A systematic review found that prenatal mercury exposure was consistently linked to lower birth weight and reduced scores on neuropsychological and developmental tests in children up to age 8.

These studies collectively demonstrate dose-dependent associations between prenatal mercury exposure and deficits in IQ, memory, attention, language, motor skills, and visual-spatial abilities that persist from infancy through school age.   To make this clear to readers, it means that the higher the mercury levels, the more the children studied lost intelligence, memory, attention, language, motor skills, and visuospatial abilities.  The effects appear even at exposure levels previously considered safe, with some evidence suggesting NO SAFE LEVEL below which mercury is without neurodevelopmental risk.

This is not theoretical risk.
This is documented developmental neurotoxicity.

Mercury Is Actively Transferred Through Breast Milk

Breastfeeding does not reduce risk — it shifts it.

Mercury is excreted into breast milk as part of maternal elimination pathways. Studies measuring mercury concentrations in lactating women show direct transfer to nursing infants, with infant exposure levels disproportionately high relative to body mass.

1. Björnberg KA, Vahter M, Berglund B, et al.    PMID: 16203251

https://pubmed.ncbi.nlm.nih.gov/16203251

Mercury passes from mother to baby through breast milk, with babies having twice as much methylmercury in their blood as their mothers at birth.

2. Ou L, Wang H, Chen C, et al.     PMID: 29574338

https://pubmed.ncbi.nlm.nih.gov/29574338

About 15% of mercury in breastfeeding mothers is eliminated through breast milk, and breastfeeding accounts for roughly 80% of mercury exposure in nursing babies.

3. Iwai-Shimada M, Satoh H, Nakai K, et al.    PMID: 25723533

https://pubmed.ncbi.nlm.nih.gov/25723533

Japanese infants received 0.08-1.68 micrograms of mercury per kilogram of body weight weekly through breast milk, with higher amounts in babies with lower body weight.

4. Grandjean P, Jørgensen PJ, Weihe P.    PMID: 9719671

https://pubmed.ncbi.nlm.nih.gov/9719671

Babies nursed for a full year had higher mercury levels in their hair, and infants may eliminate mercury slowly or not at all during their first year.

5. Bose-O'Reilly S, Lettmeier B, Shoko D, et al.    PMID: 32126374

https://pubmed.ncbi.nlm.nih.gov/32126374

In gold mining areas, 17.6-18.5% of breastfed infants received mercury doses above the safe reference level of 0.3 micrograms per kilogram of body weight daily.

6. Vollset M, Iszatt N, Enger Ø, et al.   PMID: 31063889

https://pubmed.ncbi.nlm.nih.gov/31063889

Seafood intake and dental amalgam fillings together explained 46% of the variation in mercury levels found in Norwegian mothers' breast milk.

Infants:

• Have immature hepatic and renal clearance

• Cannot conjugate or excrete mercury efficiently

• Are neurologically vulnerable during rapid brain growth

In other words, breast milk becomes a delivery mechanism for mobilized mercury.

Why “Safe Removal” Does Not Exist in Pregnancy

This is where confusion — and harm — often begins.  SMART and PROTECT protocols were developed to:

• Reduce operator exposure

• Reduce patient exposure

• Make adult amalgam removal safer

They were not designed, tested, or validated for:

• Pregnant patients

• Fetuses

• Nursing infants

Even brief increases in circulating mercury during removal represent direct fetal exposure, because redistribution occurs faster than any protective intervention.

No protocol can override placental transfer.

Chelation During Pregnancy Increases Risk — It Does Not Reduce It

Chelation and “detox support” are sometimes proposed as protective strategies. In pregnancy, they do the opposite.  Chelators:

• Mobilize mercury from tissues into circulation

• Increase blood-borne mercury levels

• Increase placental transfer during mobilization

Toxicology literature consistently shows that mobilization increases fetal exposure, even when total body burden eventually decreases. 

1. Oliveira CS, Joshee L, Zalups RK, Pereira ME, Bridges CC .  PMID: 26196528

https://pubmed.ncbi.nlm.nih.gov/26196528

Inorganic mercury crosses the placenta in a dose-dependent manner, with continued maternal exposure leading to increased fetal accumulation in kidneys, liver, and brain over time.

2. Bridges CC, Joshee L, Zalups RK .  PMID: 19615742

https://pubmed.ncbi.nlm.nih.gov/19615742

Chelation drugs DMPS and DMSA reduced mercury in both maternal and fetal tissues after methylmercury exposure, with DMPS being more effective at extracting mercury from placentas and fetuses.

3. Palkovicova L, Ursinyova M, Masanova V, Yu Z, Hertz-Picciotto I .   PMID: 17851449

https://pubmed.ncbi.nlm.nih.gov/17851449

Cord blood mercury levels were strongly linked to the number of maternal amalgam fillings and increased with more recent fillings, showing direct transfer from mother to fetus.

4. Straka E, Ellinger I, Balthasar C, et al.    PMID: 26740192

https://pubmed.ncbi.nlm.nih.gov/26740192

Mercury crosses the placenta using amino acid transporters that mistake mercury-cysteine for methionine, actively transporting mercury toward the fetal side rather than protecting against it.

These articles demonstrate that mercury crosses the placenta and accumulates in fetal tissues in a dose-dependent manner, and that chelation therapy can mobilize mercury from both maternal and fetal compartments.