Maternal perchlorate levels in women with borderline thyroid function during pregnancy and the cognitive development of their offspring: data from the Controlled Antenatal Thyroid Study

J Clin Endocrinol Metab. 2014 Nov;99(11):4291-8. doi: 10.1210/jc.2014-1901. Epub 2014 Jul 24.


Objective: Thyroid dysfunction is associated with impaired cognitive development. Perchlorate decreases thyroidal iodine uptake, potentially reducing thyroid hormone production. It is unclear whether perchlorate exposure in early life affects neurodevelopment.

Design: Historical cohort analysis.

Patients: From 2002 to 2006, 21,846 women at gestational age <16 weeks recruited from antenatal clinics in Cardiff, UK and Turin, Italy were enrolled in the Controlled Antenatal Thyroid Screening Study (CATS). We undertook a retrospective analysis of 487 mother-child pairs in mothers who were hypothyroid/hypothyroxinemic during pregnancy and analyzed whether first trimester maternal perchlorate levels in the highest 10% of the study population were associated with increased odds of offspring IQ being in the lowest 10% at 3 years of age.

Main outcome measures: Maternal urinary perchlorate, offspring IQ.

Results: Urine perchlorate was detectable in all women (median 2.58 μg/L); iodine levels were low (median 72 μg/L). Maternal perchlorate levels in the highest 10% of the population increased the odds of offspring IQ being in the lowest 10% OR = 3.14 (95% CI 1.38, 7.13) P = .006 with a greater negative impact observed on verbal OR = 3.14 (95% CI 1.42, 6.90) P = .005 than performance IQ. Maternal levothyroxine therapy did not reduce the negative impact of perchlorate on offspring IQ.

Conclusions: This is the first study using individual-level patient data to study maternal perchlorate exposure and offspring neurodevelopment and suggests that high-end maternal perchlorate levels in hypothyroid/hypothyroxinemic pregnant women have an adverse effect on offspring cognitive development, not affected by maternal levothyroxine therapy. These results require replication in additional studies, including in the euthyroid population.

Publication types

  • Randomized Controlled Trial
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Child, Preschool
  • Cognition
  • Female
  • Humans
  • Hypothyroidism / physiopathology
  • Hypothyroidism / psychology
  • Hypothyroidism / urine*
  • Intelligence*
  • Maternal Exposure
  • Neuropsychological Tests
  • Perchlorates / urine*
  • Pregnancy
  • Pregnancy Complications / physiopathology
  • Pregnancy Complications / psychology
  • Pregnancy Complications / urine*
  • Prenatal Exposure Delayed Effects / chemically induced
  • Prenatal Exposure Delayed Effects / psychology*
  • Retrospective Studies
  • Thyroid Function Tests
  • Thyroid Gland / physiopathology*


  • Perchlorates