Effects of prenatal exposure to pyrethroid pesticides on neurodevelopment of 1-year- old children: A birth cohort study in China.

Pregnant women have been ubiquitously exposed to pyrethroid pesticides. Previous studies, mainly based on third trimester measurements of maternal urinary pyrethroid metabolites, have reported inconsistent findings in the effects of prenatal pyrethroid exposure on children's neurodevelopmental outcomes. The purpose of this study was to clarify if pyrethroid exposure during the entire three trimesters of pregnancy may be associated with deleterious effects on infant neurodevelopmental status, particularly at a high dosage of exposure. We measured maternal urinary concentrations of pyrethroid metabolites in all trimesters of pregnancy and assessed children's neurodevelopment at one year of age using the Bayley Scales of Infant and Toddler Development, Third Edition (BSID-III). Multiple linear regression models were used to estimate the effects of metabolites (3-PBA, 4 F-3-PBA, cis-DBCA) in each trimester on BSID-III composite scores. Logistic regression analyses were applied to predict developmental delay vs non-delayed status (cut-off composite score of below 80 for developmental delay) based on the maternal levels of pyrethroid metabolites. In the first, second and third trimesters of pregnancy, the detection rates of pyrethroid metabolites were 94.7%, 90.7%, and 89.0%; the 50th percentiles of exposure level were 0.24 µg/g, 0.24 µg/g and 0.21 µg/g for 3-PBA, 0.14 µg/g, 0.17 µg/g and 0.15 µg/g for 4 F-3PBA, 0.21 µg/g, 0.25 µg/g and 0.19 µg/g for cis-DBCA respectively. In the second trimester, 3-PBA was inversely associated with Cognition and Language scores [ß = -3.34 (95% CI = -6.11, -0.57) and ß = -2.90 (95% CI = -5.20, -0.61), respectively], and significantly increased the risk of Cognition and Language developmental delay [OR= 1.64 (95% CI = 1.03, 2.62) and OR = 1.52 (95% CI = 1.06, 2.19), respectively]; cis-DBCA was inversely associated with Adaptive Behavior scores [ß = -0.73 (95% CI = -1.27, -0.19)], and significantly increased the risk of Adaptive Behavior developmental delay [OR= 1.11 (95% CI = 1.02, 1.21)]. When the maternal levels of pyrethroid metabolites were stratified into the regression models according to the 90th percentile of exposure, in the first trimester, Cognition and Motor scores were inversely associated with higher cis-DBCA [ß = -7.19 (95% CI = -12.97, -1.41) and ß = -8.20 (95% CI = -13.35, -3.05), respectively], Language scores were inversely associated with higher 3-PBA [ß = -6.01 (95% CI = -10.96, -1.06)]; in the second trimester, Cognition scores were inversely associated with higher cis-DBCA [ß = -6.64 (95% CI = -12.51, -0.76)], Language scores were inversely associated with higher 3-PBA [ß = -5.17 (95% CI = -10.07, -0.27)] and cis-DBCA [ß = -5.40 (95% CI = -10.28, -0.52)]. We concluded that pyrethroid exposure in the first and second trimesters was associated with poorer infants neurodevelopmental outcomes at one year of age, and these effects were particularly pronounced at high levels of pyrethroid exposure.