Deltamethrin Placental Transfer and Seasonal Pyrethroid Exposure: A Mother-Newborn Dyad Pilot Study

The aim of this study was to assess the presence of pyrethroid metabolites in the urine of mothers and their full-term newborns during the first days of life and to investigate the correlation between maternal and neonatal urinary concentrations. It also explores potential clinical and environmental factors influencing these levels.

Creatinine-adjusted urinary concentrations of 5 pyrethroid metabolites, 3-phenoxybenzoic acid, 4-fluoro-3-phenoxybenzyl acid (FPBA), cis-3-(2,2-dibromovinyl)-2,2-dimethylcyclopropane-carboxylic acid, and cis and trans-3-(2,2-dichlorovinyl)-2,2-dimethylcyclopropane-1-carboxylic acid (Cis-dimethylcyclopropane-1-carboxylic acid), and (Trans-dimethylcyclopropane-1-carboxylic acid), were measured within the first 3 days postpartum in mothers and their children.

The study included 88 mothers and 91 full-term newborns. At least 1 pyrethroid metabolite was detected in 99% of mothers and 77% of newborns. A significant (P < 0.05) correlation was observed between maternal and neonatal urinary concentrations of dimethylcyclopropane-carboxylic acid, a metabolite specific to deltamethrin, supporting the hypothesis of placental transfer. Newborns born during winter had considerably lower urinary metabolite concentrations compared with those born in other seasons. No significant correlations were found for the other metabolites, likely due to the diversity of their parent compounds.

This study provides evidence of transplacental transfer of deltamethrin, while the lack of 3-phenoxybenzoic acid correlation suggests differential metabolic or exposure pathways for nonspecific metabolites. The seasonal variation in metabolite levels suggests environmental or behavioral factors influencing exposure. These findings emphasize the need to investigate dietary and domestic pesticide exposure as key contributors to perinatal pyrethroid exposure, as well as longitudinal studies to assess the evolution of metabolite concentrations and their potential health effects on mothers and infants.