Prenatal pyrethroid insecticide exposure and thyroid hormone levels and birth sizes of neonates.

Pyrethroid insecticides have been shown to possess thyroid hormone disrupting properties in previous animal studies. In this study, the relationship between maternal exposure to pyrethroid insecticides during pregnancy and neonatal thyroid hormone status (free thyroxine (fT4) and thyroid stimulating hormone (TSH) in whole blood) and birth sizes were explored in 147 mother-neonate pairs in Tokyo. The concentration of 3-phenoxybenzoic acid (3-PBA) in maternal urine, sampled in the first trimester of gestation, was used for pyrethroid exposure assessment.

Associations between levels of hydroxylated PCBs and PCBs in serum of pregnant women and blood thyroid hormone levels and body size of neonates.

The purpose of this study was to investigate possible associations between concentrations of hydroxylated PCBs (OH-PCBs) and PCBs in the serum of women in the first trimester of pregnancy and thyroid hormone levels and body size of newborn infants in 79 mother-neonate pairs. We measured 16 OH-PCB isomers and 29 PCB isomers in the serum of Japanese women sampled at 11.1±1.