Background/aim Little is known about the association between maternal exposure during pregnancy to organophosphate pesticides (OP) and fetal growth. We aimed to study whether maternal exposure to the dialkyl phosphate (DAP) metabolites during the first half of pregnancy was associated with fetal growth as estimated by ultrasonographic prenatal examinations (US).

Methods An ongoing cohort study of pregnant women recruited at 11–18 weeks of gestation, who were interviewed and gave a urine specimen upon recruitment. In order to analyse the fetal growth, we used repeated US fetal measurements of head circumference (HC), femur length (FL), abdominal circumference (AC) and biparietal diameter (BPD). Urine specimens were analysed for DAP metabolites in the Institute for Occupational, Social and Environmental Medicine of the University Erlangen-Nürnberg, Germany. Linear and mixed linear models (with DAP, gestational age and gender as fixed effects and mothers as random effects) were constructed to study the associations between OP exposure and US measurements.

Results A total of 826 US measurements were conducted in 211 women for each of the four US parameters. 165 women had more than two US measurements and 99 women had 4–7 measurements during pregnancy. Linear regression models for the association between DAP and the last US measurement adjusting for gender, suggested negative associations; HC (ß=-15.3, p=0.07), FL (ß=-3.8, p=0.07), AC (ß=-15.3, p=0.08), BPD(ß=-4.06, p=0.08). Mixed linear models with all US data did not support any association between maternal DAP level and fetal growth (HC: ß=-0.21, std=1.03, p=0.8; FL: ß=-0.01, std=0.23, p=0.9; AC: ß=-0.03, std=1.23, p=0.9; and BPD: ß=0.05, std=0.31, p=0.8).

Conclusion In this preliminary analysis, there was a suggested inverse association between DAP exposure and fetal growth. To our knowledge, this analysis is the first to use repeated fetal measurements and early maternal DAP levels. Further analyses controlling for gestational age will be conducted.