Objective  To investigate the association of maternal exposure to particulate matter less than 2.5 μm in aerodynamic diameter (PM_2.5) during whole pregnancy with neurodevelopment of one-year-old children.

  Methods  We recruited 318 mother-child pairs from a cohort study on association of pregnancy PM_2.5 exposure with pregnant outcome and childhood glycolipid metabolism conducted from 2014 through 2017 in rural Yunnan. From the cohort study, the data on individual exposure of pregnant women to PM_2.5 in the first, second, and third trimester pregnancy were collected. The children were tracked from birth to one year of age and the children′s development in cognition, language, and motor function were assessed at one year of age using the Bayley Scales of Infant and Toddler Development, Third Edition (BSID-III). Multivariate binary logistic regression model was adopted to analyze the relationship between maternal PM_2.5 exposure in three trimesters and the developmental delay in various fields of neurodevelopment among the children at one year of age.

  Results  The average daily medians (interquartile range IQR) of PM_2.5 exposure (μg/m³) were 25.56 (22.46 − 31.12), 24.90 (21.16 − 30.41), and 25.23 (21.9 − 30.08) for the pregnant women in the first, second, and third trimester, with the highest daily averages of 71.86, and the instantaneous peak values (IQR) of 297.37 (170.57 − 417.21), 277.75 (138.72 − 411.12), and 290.63 (162.08 − 421.06) for the three trimesters. The children′s mean BSID-III scores for cognition, language, and motor function at one year of age were 100.52 ± 16.91, 94.03 ± 14.94, and 94.32 ± 15.04 and the proportions of the children with delayed development of cognition, language and motor function were 7.52%, 20.69%, and 15.04%, respectively. Multivariate linear regression analysis showed that there was no significant associations of maternal PM_2.5 exposure in three trimesters with children′s scores of cognition, language and motor function. Multivariate binary logistic regression analysis indicated that a 1 μg/m³ increment in average maternal daily PM_2.5 exposure in the second trimester was correlated with increased children′s risk of delayed motor developmental function (odds ratio = 1.039, 95% confidence interval: 1.001 − 1.077). But no associations of maternal instantaneous peak PM_2.5 exposure in three trimesters with delayed development of the three functional dimensions were observed among the one-year-old children.

  Conclusion  Within China′s quality standards for ambient air PM_2.5 level, the average maternal daily PM_2.5 exposure in the second trimester of pregnancy is a risk for delayed development of motor function of children at one year of age. But high level of transient PM_2.5 exposure during pregnancy does not affect the cognition, language, and motor function development of children at one year of age.