Objective  To preliminaryly explore the effect of maternal air pollution exposure in different pregnancy periods on birth weight of neonates in urban area Shijiazhuang city, Hebei province.

  Methods  The data on 3 407 pregnant women and their newborns delivered between August 2013 and December 2017 were obtained from a grade A tertiary hospital in Shijiazhuang city; the daily air pollution data during the same period were also collected. The effects of exposure to different pollutants during early pregnancy, second and trimester, and throughout pregnancy on the birth weight of the newborns were analyzed.

  Results  Among all the newborns, the incidence rate of low birth weight (LBW) was 9.51%; the birth weight of the neonates was influenced by maternal age, education, neonates′ gender and year of birth; maternal age, education, and parity were influence factors of LBW. The results of multivariate linear regression analysis showed that there were significant differences in the effect of exposure to different pollutants on neonatal birth weight during different pregnancy periods. A decrease of 26.6, 7.2, 4.4, 5.7, 8.1, 2.8, and 6.0 grams in birth weight were associated with an increment of 10 unit in average levels exposure to air quality index (AQI), particulate matter less than 2.5 μm in aerodynamic diameter (PM_2.5), particulate matter less than 10 μm in aerodynamic diameter (PM₁₀), sulfur dioxide (SO₂), nitrogen dioxide (NO₂), carbon monoxide (CO), and ozone (O₃) during the first trimester; a decrease of 12.7, 6.3, and 4.7 grams in birth weight were associated with an increment of 10 unit in the average level of exposure to PM_2.5, PM₁₀, and SO₂ during second trimester; a decrease of 1.3 grams in birth weight was associated with an increment of 10 unit in the average level of exposure to SO₂ during third trimester; a decrease of 8.3, 6.3, 5.5, 1.3 grams in birth weight were associated with an increment of 10 unit in the average level of exposure to PM_2.5, PM₁₀, SO₂, NO₂ during entire pregnancy, respectively.

  Conclusion  Maternal exposure to air pollutants during pregnancy can significantly decrease birth weight of newborns; the adverse effects of the exposure to PM_2.5, PM₁₀ or SO₂ on LBW are more obvious and first and second trimester may be the critical period for the hazardous effect of maternal air pollution on birth weight of newborns.