Objective To explore the influence of maternal exposure to chlorpyrifos during pregnancy on neuro-developmental abnormalities of children at age of 2 years for health risk assessment and control of maternal chlorpyrifos exposure.

Methods The participants of the study were 893 healthy mother-infant pairs enrolled in the Health Baby Birth Cohort in Wuhan municipality, Hubei province from January 2014 through June 2017. Urine samples (n = 2679) were collected from all the surveyed mothers at first, second, and third trimester of pregnancy for detection of 3, 5, 6-trichloro-2-pyridinol (TCPy, a specific metabolite of chlorpyrifos) by high-performance liquid chromatography coupled with tandem mass spectrometry to evaluate internal exposure of chlorpyrifos. The mental development index (MDI) and psychomotor development index (PDI) of surveyed children at age of 2 years were measured using domestically modified Bayley Scales of Infant Development (BSID-CR). The correlation between the children′s neurodevelopmental abnor-malities and maternal chlorpyrifos exposure during pregnancy was analyzed.

Results The mean scores of MDI and PDI were 110.0 ± 21.7 and 111.0 ± 17.1 for all the 2-year-old children and 99 (11.1%) and 23 (2.58%) of the children were assessed as having abnormal mental and psychomotor development (with the MDI or PDI score of less than 80), respectively. The median (25th percentile, 75th percentile) of urine specific gravity adjusted concentration (ng/mL) of TCPy for urine samples the mothers in the first, second, and third trimesters were 2.02 (1.30, 3.38), 1.58 (0.98, 2.45), and 1.29 (0.79, 2.05), with the detection rate of 99.4%, 98.8%, and 95.9%, respectively. After adjusting for age at delivery, pre-pregnancy body mass index, maternal education, passive smoking during pregnancy, folic acid supplementation during pregnancy, child sex, parity, breastfeeding duration, and season of urine sample collection, the results of the multifactorial generalized estimating equation analysis indicated that each two-fold increase in maternal urinary TCPy concentration at first trimester was associated with the increased risks of mental and psychomotor developmental abnormalities for all the mothers′ children of 2-year-old, with the odds ratio (OR) and 95% confidence interval (95%CI) of 1.15 (95%CI: 1.01 – 1.32) and 1.34 (95%CI: 1.04 – 1.73); while, for the mother′s boys of 2-year-old, each two-fold increase in maternal urinary TCPy concentration at first trimester was correlated with increased risk of psychomotor developmental abnormality (OR = 1.47, 95%CI: 1.09 – 1.99).

Conclusion Maternal exposure to chlorpyrifos during pregnancy, especially in the first trimester, could lead to neurodevelopmental abnormalities in children at age of 2 years, with a more pronounced effect on the neurodevelopment of boys.