Chemical Mixtures Suppress Thyroid Function in Pregnancy

Pregnant women exposed to a mix of everyday chemicals had lower thyroid hormone levels. And thyroid hormones are critical for fetal brain development.

26 Chemicals Tested Together

A 2026 study in Int J Hyg Environ Health measured exposure to 26 endocrine-disrupting chemicals in 1,970 pregnant women from the Swedish SELMA study. Instead of testing each chemical alone, they analyzed them as a mixture.

The mixture approach revealed effects that single-chemical analysis might miss.

Lower Thyroid Hormones Across the Board

Higher EDC mixture exposure was linked to lower FT3 (free triiodothyronine), driven mainly by PCBs. It was also linked to lower TT3 (total triiodothyronine), driven by PFOS.

T3 is the active form of thyroid hormone. Your developing baby depends on it for brain growth, organ formation, and metabolic regulation. Lower T3 during pregnancy means the baby's brain may not get what it needs.

Why Mixtures Matter More

Testing one chemical at a time underestimates the real damage. Your body doesn't encounter PFOS alone or PCBs alone. It gets hit with dozens of chemicals simultaneously. When researchers tested them as a group, the thyroid-suppressing effect became clear.

What Pregnant Women Can Do

Avoid PFAS-contaminated water (use a certified filter). Reduce PCB exposure by limiting high-fat fish from contaminated waters. Cut out unnecessary plastic in food storage and cooking. And switch to non-toxic baby products before the baby arrives.

Also see glass food storage for safer alternatives.

Source: Derakhshan et al. (2026). Int J Hyg Environ Health.