A peer-reviewed study conducted by researchers at the University of Miami, Clean Label Project, and Ellipse Analytics, yielded concerning results about the prevalence of heavy metal contamination in prenatal supplements.

The authors of the study, published in Environmental Research, found that 83% of 156 over-the-counter and nine prescription prenatal products contained detectable amounts of lead, with 15% of those exceeding California’s Proposition 65 threshold of 0.5 micrograms per serving.

Nearly three-quarters (73%) of products were found to contain cadmium, which is a known reproductive toxicant. Additionally, phthalates, a class of endocrine-disrupting chemicals, were detected in over 25% of products, the authors of the study found.

Prescription products didn’t appear to offer a guarantee of safety, with three of the nine products testing positive for lead at levels greater than the Prop 65 threshold.

“These findings are deeply concerning given that prenatal vitamins are taken daily by pregnant people during a period of critical fetal development,” said Jaclyn Bowen, executive director of the Clean Label Project and co-author of the study. “Toxic exposure in utero has long-term impacts on cognitive, behavioral, and metabolic health. We must do better.”
 

Clean Label Project reports that there is an urgent need for legislation at both the federal and state level which provides enforceable heavy metal limits and greater testing of prenatal vitamins.

Recently, California lawmakers advanced Senate Bill 646, which would mandate that every lot of a finished prenatal vitamin product is tested by manufacturers for arsenic, cadmium, lead, and mercury at a proficient, ISO-accredited laboratory. The bill would require manufacturers to disclose product testing results, and would create a new crime to prohibit a person or entity from selling, manufacturing, delivering, holding, or offering for sale any prenatal vitamins that don’t comply with testing requirements.

“We applaud Senator [Weber] Pierson’s leadership in authoring SB 646,” said Bowen. “This bill builds on the momentum of AB 899 [a similar bill for infant formula] and ensures that pregnant people have the same right to transparency as parents buying baby food. It’s common sense; if we’re going to protect babies, we must also protect them before they’re born. Science shows us that the first 1,000 days of life, starting in the womb, are foundational to a child’s future and inextricably linked to the health of the mother. Regulatory efforts aimed at baby food safety have fallen short by failing to consider that this critical window begins at conception, not just at birth. We can’t wait any longer to act.”

Context is Key

It’s important to look at the relative prevalence and potency of heavy metal contamination in the prenatal products tested, compared to dietary supplements and foods at large, noted Jeff Ventura, vice president of communications at the Council for Responsible Nutrition.

“The findings – 15% of over-the-counter prenatal vitamins and 33% of prescription prenatal vitamins exceeding California Proposition 65’s lead threshold of 0.5 µg/day – are not outliers when compared to other categories of food. For example, as acknowledged in the study, the FDA’s limit for lead in candy is 100 ppb (parts per billion). It’s important to recognize that Prop 65 levels are extremely conservative, incorporating a 1,000-fold safety factor, and designed to trigger labeling at levels far below those associated with known health effects.”

Some other thresholds more relevant to human safety risk include FDA’s interim reference levels for lead and cadmium; USP limits for elemental impurities; and the NSF/ANSI 173 and USP Verified Mark standards, which are used in third-party certification programs and “acknowledge environmental realities,” Ventura said.

The most prevalent causes of heavy metal detection in dietary supplements is typically the presence of mineral-based ingredients, or raw agricultural materials, where higher levels of trace elements naturally occur, Ventura said. “The strong correlations in this study between calcium/iron content and lead/cadmium levels are consistent with these known exposure pathways.”

While the Clean Label Project advocated for California’s Senate Bill 646 in response to the findings of the study, “we caution against drawing sweeping regulatory conclusions, or enacting onerous and impractical requirements, from a single observational study, especially one that did not assess toxicological outcomes or cumulative risk. Instead, this study underscores the importance of robust quality assurance practices by manufacturers and the need for consistent national standards. CRN has long advocated for harmonized federal policies over state-by-state patchworks like Prop 65, which can create confusion for both consumers and manufacturers,” said Ventura. Those policies should include stronger enforcement of Good Manufacturing Practices (GMPs), broader consumer education, and federal leadership in setting science-based limits which “reflect the realities of our environment,” he noted.

With that said, he noted that the study reinforces the need for manufacturers to remain vigilant in sourcing, testing, and manufacturing practices to keep contaminants at a minimum; that consumers shouldn’t been alarmed or avoid prenatal vitamins which have a vital role in maternal and fetal health; and that consumers should verify whether their prenatal vitamins omit or reduce certain nutrients from a formulation to achieve lower heavy metals, instead requiring users to get those nutrients from other sources.