Researchers studied 728 mother-child pairs in China to understand how common industrial chemicals called PFAS affect children’s thinking and learning abilities. They found that when pregnant women had low vitamin D levels, their babies—especially boys—showed lower scores on thinking and learning tests if they were exposed to high levels of PFAS. However, mothers with healthy vitamin D levels seemed to have some protection against these harmful effects. This suggests that getting enough vitamin D during pregnancy might help protect a baby’s developing brain from these chemicals.

The Quick Take

  • What they studied: Whether common industrial chemicals called PFAS that pregnant women are exposed to can affect how well their children think and learn, and whether vitamin D can reduce this risk.
  • Who participated: 728 pregnant women and their children from China, followed from 2013 to 2014. Children were tested for thinking and learning skills between ages 2.7 and 6 years old.
  • Key finding: Boys whose mothers had low vitamin D during pregnancy and were exposed to high levels of PFAS had lower thinking and learning scores. Girls showed different patterns. Mothers with healthy vitamin D levels appeared to have some protection.
  • What it means for you: If you’re pregnant or planning to become pregnant, maintaining healthy vitamin D levels may help protect your baby’s brain development from industrial chemicals. However, this research is from one study in China, so talk to your doctor about your individual situation.

The Research Details

This was a cohort study, which means researchers followed a group of pregnant women and their children over time to see what happened. The researchers measured the levels of PFAS chemicals and vitamin D in the mothers’ blood during each trimester of pregnancy (three times during the 9 months). They then tested the children’s thinking and learning abilities when they were between 2.7 and 6 years old using standard tests. The researchers used advanced statistical methods to figure out whether the chemicals affected the children’s brain development and whether vitamin D made a difference.

The study measured multiple types of PFAS chemicals because these substances are found in many everyday products like non-stick cookware, food packaging, and water-resistant clothing. By measuring vitamin D at multiple points during pregnancy, the researchers could get a better picture of the mother’s overall vitamin D status during the entire pregnancy.

This approach is important because it allowed researchers to see the real-world effects of chemical exposure during pregnancy, rather than just testing in a lab. By measuring chemicals multiple times throughout pregnancy and testing children years later, they could better understand how prenatal exposure affects long-term brain development. The stratification by sex and vitamin D status helped reveal that the effects weren’t the same for everyone.

This study has several strengths: it included a reasonably large number of families (728), measured chemicals multiple times during pregnancy for accuracy, and used validated tests to measure children’s cognitive abilities. However, the study was conducted in China, so results may not apply equally to other populations. The researchers adjusted for many other factors that could affect brain development, which strengthens the findings. The study is observational, meaning it shows associations but cannot prove that PFAS directly causes lower scores.

What the Results Show

The researchers found that boys whose mothers had high exposure to certain PFAS chemicals during pregnancy had lower scores on thinking and learning tests. Specifically, three types of PFAS chemicals were linked to lower scores: br-PFOA affected verbal thinking skills, 8:2 Cl-PFESA affected visual thinking skills, and n-PFHxS affected working memory (the ability to hold information in your mind temporarily). When looking at all the PFAS chemicals together as a mixture, boys showed lower overall cognitive scores.

Interestingly, girls showed a different pattern. Some PFAS chemicals were actually associated with higher cognitive scores in girls, particularly when their mothers had low vitamin D. This sex difference is important and suggests that boys and girls may respond differently to chemical exposure during pregnancy.

The most important finding was about vitamin D. When mothers had vitamin D deficiency (less than 20 ng/mL), the harmful effects of PFAS on boys’ brain development were much stronger. In contrast, when mothers had adequate vitamin D levels, the harmful effects were reduced or not present. For girls, the pattern was reversed—associations with PFAS were only seen in the vitamin D deficient group.

The specific numbers showed that for every increase in PFAS mixture levels, boys’ thinking scores dropped by about 2-3 points on standard tests when mothers had low vitamin D. This may seem small, but these differences can add up over time and affect school performance.

The study examined different types of cognitive abilities separately: verbal comprehension (understanding words and language), visual-spatial skills (understanding shapes and space), and working memory (holding information temporarily). Different PFAS chemicals affected different cognitive abilities, suggesting that various chemicals may harm the brain in different ways. The researchers also found that the effects were dose-dependent, meaning higher chemical exposure was linked to greater reductions in cognitive scores.

Previous research has suggested that PFAS chemicals may harm brain development, but most studies looked at only one or two chemicals rather than the entire mixture of chemicals that people are actually exposed to. This study is more comprehensive because it examined multiple PFAS chemicals together. The finding that vitamin D may be protective is relatively new and suggests a potential way to reduce harm. The sex-specific differences found here align with some previous research suggesting that boys may be more vulnerable to certain environmental exposures during brain development.

This study has several important limitations. First, it was conducted in China, so the results may not apply the same way to other countries with different diets, lifestyles, and chemical exposures. Second, the study measured vitamin D and PFAS at specific times during pregnancy, but exposure varies throughout the day and season, so these measurements may not capture the full picture. Third, the study cannot prove that PFAS causes lower cognitive scores—it only shows that they are associated. Other unmeasured factors could explain the relationship. Fourth, the study tested children at different ages (2.7 to 6 years), which could affect results. Finally, the number of mothers with adequate vitamin D was relatively small (92 out of 728), making it harder to draw strong conclusions about the protective effect.

The Bottom Line

Based on this research, pregnant women should aim to maintain adequate vitamin D levels (at least 20 ng/mL). This can be achieved through sun exposure, vitamin D-rich foods like fatty fish and fortified milk, or supplements as recommended by a doctor. Additionally, reducing exposure to PFAS chemicals when possible—such as avoiding non-stick cookware, choosing products without water-resistant coatings, and being mindful of food packaging—may help protect fetal brain development. However, these recommendations should be discussed with your healthcare provider, as individual needs vary. The confidence level is moderate because this is one study in a specific population.

Pregnant women and women planning to become pregnant should pay attention to these findings, particularly if they live in areas with known PFAS contamination or have low vitamin D levels. Parents of young children may also find this information useful for understanding their child’s development. Healthcare providers should consider checking vitamin D levels during prenatal care. The general public should be aware that these chemicals are widespread in consumer products, though the actual risk to any individual is still being studied.

The effects of prenatal PFAS exposure on brain development appear to be measurable by age 2-3 years, as shown in this study. However, the long-term effects throughout childhood and into adulthood are not yet fully understood. It may take years of additional research to know whether these early differences in test scores predict long-term learning or developmental outcomes.

Want to Apply This Research?

  • Track vitamin D levels quarterly (every 3 months) if pregnant or planning pregnancy. Record serum vitamin D concentration in ng/mL and set a goal of maintaining levels above 20 ng/mL. Note any supplementation or dietary sources of vitamin D.
  • Users can log daily vitamin D intake through food sources (fatty fish, fortified milk, egg yolks) and supplements. Set reminders for sun exposure (10-30 minutes daily when possible) and track supplementation adherence. For those concerned about PFAS exposure, users can log efforts to reduce exposure such as switching to stainless steel cookware, choosing products without water-resistant coatings, and selecting fresh foods over packaged options.
  • Create a pregnancy wellness dashboard that tracks vitamin D status alongside other prenatal markers. Set monthly reminders to discuss vitamin D levels with healthcare provider. For parents of young children, track developmental milestones and cognitive assessments at recommended intervals (ages 2-3, 4-5, and 6 years) to monitor normal development. Log any concerns about learning or development to discuss with pediatrician.

This research suggests an association between prenatal PFAS exposure and child cognitive development, with potential modification by vitamin D status, but does not prove causation. This information is for educational purposes only and should not replace professional medical advice. Pregnant women or those planning pregnancy should discuss vitamin D supplementation, PFAS exposure reduction, and any concerns about fetal development with their healthcare provider. Individual risk varies based on location, diet, lifestyle, and other factors. If you have concerns about chemical exposure or your child’s development, consult with your doctor or pediatrician for personalized guidance.