Twin pregnancies are particularly vulnerable to chemical exposures such as per- and polyfluoroalkyl substances (PFAS), yet mechanistic evidence linking PFAS to adverse pregnancy outcomes remains limited. In this study, we examined maternal and cord serum PFAS exposure in relation to thyroid function, placental pathology, and fetal growth in a subset of twins from the Ideal Breastmilk (IBM) cohort in Korea (78 mothers, 199 neonates). Cord serum PFAS exposure was associated with a thyroid hormone profile characterized by higher FT4 and lower TSH within the reference range. In addition, higher cord PFOA, PFNA, and ∑PFCA concentrations were associated with lower birth weight. Maternal concentrations of these PFAS were highest in pregnancies with severe placental malperfusion (maternal vascular underperfusion, MVU). Placental gene expression analysis revealed reduced CD31 and MCT8 expression and elevated DIO3 expression in association with PFAS exposure and pathology, suggesting impaired placental vascular-endocrine function and disrupted maternal–fetal thyroid hormone transport. Together, these findings provide mechanistic evidence linking PFAS exposure to fetal growth impairment in twin pregnancies. Our observations highlight the heightened vulnerability of twin pregnancies to environmental chemical exposures and underscore the need for strengthened exposure mitigation strategies during pregnancy.
Chae et al. (Tue,) studied this question.