Study suggests link between prenatal mercury exposure and autism: Could a common pregnancy shot containing thimerosal increase autism risk?

By oliviacook // 2025-03-08

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A late 20th century debate questioned whether Rho(D)-immune globulin, a common prenatal treatment containing thimerosal (a mercury-based preservative) was linked to rising autism spectrum disorder (ASD) rates.
Researchers from the Institute for Chronic Illnesses examined 53 children with autism, all non-Jewish Caucasians born between 1987 and 2001, to explore a potential connection between prenatal mercury exposure from thimerosal and autism development.
The study found that children with autism were more than twice as likely to have Rh-negative mothers (28.3 percent vs. 14.36 percent in the control group), with an odds ratio of 2.35, suggesting a higher risk for autism in children with Rh-negative mothers who received thimerosal-containing pregnancy shots.
Mercury can cause neurological issues, behavioral changes and motor dysfunction. Thimerosal can cross the placental and blood-brain barriers, potentially affecting fetal brain development.

For decades, the medical community has worked to understand the complex causes of autism spectrum disorders (ASDs). While genetics play a key role, environmental factors – especially prenatal exposures – have also been widely studied. One such factor is thimerosal, including a widely administered injection for Rh-negative pregnant women. In the late 20th century, a debate emerged about whether a common prenatal treatment could be linked to the rising rates of autism spectrum disorders. The treatment, known as Rho(D)-immune globulin, was widely used to prevent a serious condition called Rh disease in newborns. However, until the early 2000s, many versions of this shot contained thimerosal, a preservative made with mercury. A study published in the Journal of Maternal-Fetal and Neonatal Medicine aimed to explore whether there is a connection between this mercury exposure and the development of autism. Researchers from the Institute for Chronic Illnesses conducted a study involving 53 children with autism, all of whom were non-Jewish Caucasians born between 1987 and 2001. These children were evaluated at the Genetic Centers of America, where they underwent thorough testing to rule out other potential causes of their autism. To understand the role of thimerosal, the researchers focused on the mothers of these children. They found that every mother had received a Rho(D)-immune globulin shot during pregnancy and these shots contained thimerosal. To put this into perspective, imagine a group of children with autism and every single one of their mothers had been exposed to this mercury-containing compound while pregnant. For comparison, the researchers also looked at a group of 926 non-Jewish Caucasian women who had visited the same centers for prenatal care between 1980 and 1989. They found that about 14 percent of these women were Rh-negative, meaning they could benefit from the Rho(D)-immune globulin shot.

Mercury and the brain: The science behind the connection

The study revealed a striking difference: children with autism were more than twice as likely to have Rh-negative mothers compared to children without autism. Specifically, 28.3 percent of the mothers of children with autism were Rh-negative, while only 14.36 percent of the control group mothers were Rh-negative. This translates to an odds ratio of 2.35, meaning the risk was significantly higher for children with autism. Every Rh-negative mother of a child with autism had received at least one thimerosal-containing Rho(D)-immune globulin injection while pregnant. These findings suggest a possible link between material Rh status, prenatal exposure to thimerosal and autism risk. Mercury is a well-documented neurotoxin. Research has shown that mercury exposure can impact fetal brain development in several ways:

Neurotoxicity - Mercury can interfere with normal neuronal growth (brain development) and connectivity or problems with brain function.
Behavioral changes - Studies have linked mercury to traits commonly observed in autism, including repetitive behavior and challenges with social interaction and communication.
Motor and cognitive effects - Prenatal mercury exposure has been associated with developmental delays, motor dysfunction (difficulties with movement and coordination) and learning difficulties.

A key concern with thimerosal is its ability to cross both the placental and blood-brain barriers, meaning that mercury could reach the developing fetus and accumulate in brain tissue. Animal studies have shown that ethylmercury (the form found in thimerosal) is readily transferred from mother to fetus and can persist in the brain long after exposure. This study aligns with previous research suggesting a connection between prenatal mercury exposure and neurodevelopmental disorders. A 2003 study by Holmes et al. found that mothers of autistic children had a significantly higher rate of Rh-negativity (46 percent) compared to control (nine percent). Animal studies have demonstrated that prenatal exposure to thimerosal can lead to neurological and behavioral changes similar to those seen in autism. Molecular studies have shown that even low levels of thimerosal can cause neuronal damage, disrupt key pathways and alter brain structure. Additionally, in 2004, the California Environmental Protection Agency classified thimerosal as a developmental toxin, recognizing its potential to cause neurological and behavioral effects in children. While the study suggests a possible link between thimerosal exposure and autism, it has not established causation. The researchers emphasize the need for more studies to confirm their findings and explore other potential factors. (Related: Vaccine industry in panic over global effort to remove all mercury from vaccines.) Note: This article simplifies complex scientific findings for general understanding. Always consult a healthcare professional regarding pregnancy-related concerns. Watch this video about the danger of thimerosal in vaccines. This video is from the Vaccines and Vaccination channel on Brighteon.com.

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Mercury and the brain: The science behind the connection

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