Pregnant women with higher blood levels of a common flame retardant could have altered thyroid hormone levels during pregnancy, a new study has found.
According to the researchers this is the first study, which has sufficient sample size to assess the correlation between PBDE flame-retardants and thyroid function in pregnant women.
PBDEs, or polybrominated diphenyl ethers, are a class of organobromine compounds found in household items such as carpets, textiles, foam furnishings, electronics and plastics etc.
"Normal maternal thyroid hormone levels are essential for normal fetal growth and brain development, so our findings could have significant public health implications. These results suggest that a closer examination between PBDEs and these outcomes is needed," said the study's lead author, Jonathan Chevrier, a University of California, Berkeley researcher in epidemiology and in environmental health sciences.
In the new study, the researchers analysed blood samples of as many as 270 women taken around the end of their second trimester of pregnancy.
The researchers found that a 10-fold increase in each of the PBDE chemicals was associated with decreases in TSH ranging from 10.9 percent to 18.7 percent.
When the five PBDEs were analysed together, a tenfold increase was linked to a 16.8 percent decrease in TSH.
The study did not find major effect of PBDE concentrations on levels of T4.
With one exception- all the women in the study with low TSH levels had normal free T4 levels, which corresponds to the definition of subclinical hyperthyroidism.
The study found that odds of subclinical hyperthyroidism increased 1.9 times for each tenfold increase in PBDE concentrations.
This study was published in the journal Environmental Health Perspectives.