Prenatal organophosphate pesticide exposure and sex-specific estimated fetal size.

Prenatal organophosphate (OP) pesticide exposure may be associated with reduced fetal growth, although studies are limited and have mixed results. We investigated associations between prenatal OP pesticide exposure and fetal size and modification by fetal sex. Maternal urinary concentrations of dialkyl phosphate (DAP) metabolites were measured at 3 time points. Fetal biometrics were obtained from ultrasounds in the second (n = 773) and third (n = 535) trimesters. Associations between pregnancy-averaged ΣDAP and fetal biometry z scores were determined through multiple linear regression. Modification by sex was investigated through stratification and interaction. In the second trimester, one ln-unit increase in ΣDAP was associated with lower estimated fetal weight (-0.15 SD; 95% CI, -0.29 to -0.01), head circumference (-0.11 SD; CI, -0.22 to 0.01), biparietal diameter (-0.14 SD; CI, -0.27 to -0.01), and abdominal circumference (-0.12 SD; CI, -0.26 to 0.01) in females. In the third trimester, one ln-unit increase in ΣDAP was associated with lower head circumference (-0.14 SD; CI, -0.28 to 0.00) and biparietal diameter (-0.12 SD; CI, -0.26 to 0.03) in males. Our results suggest that prenatal OP pesticide exposure is negatively associated with fetal growth in a sex-specific manner, with associations present for females in mid-gestation and males in late gestation. This article is part of a Special Collection on Environmental Epidemiology.