Impact of ambient air pollution exposure during pregnancy on adverse birth outcomes: generalized structural equation modeling approach

Abstract

Background: Air pollution and several prenatal factors, such as socio-demographic, behavioural, physical activity and clinical factors influence adverse birth outcomes. The study aimed to investigate the impact of ambient air pollution exposure during pregnancy adjusting prenatal risk factors on adverse birth outcomes among pregnant women in MACE birth cohort.

Methods: Data for the study was obtained from the Mother and Child in the Environment (MACE) birth cohort study in Durban, South Africa from 2013 to 2017. Land use regression models were used to determine household level prenatal exposure to PM_2.5, SO₂ and NOx. Six hundred and fifty-six births of pregnant females were selected from public sector antenatal clinics in low socio-economic neighbourhoods. We employed a Generalised Structural Equation Model with a complementary log-log-link specification.

Results: After adjustment for potential prenatal factors, the results indicated that exposure to PM_2.5 was found to have both significant direct and indirect effects on the risk of all adverse birth outcomes. Similarly, an increased level of maternal exposure to SO₂ during pregnancy was associated with an increased probability of being small for gestational age. Moreover, preterm birth act a mediating role in the relationship of exposure to PM_2.5, and SO₂ with low birthweight and SGA.

Conclusions: Prenatal exposure to PM_2.5 and SO₂ pollution adversely affected birth outcomes after controlling for other prenatal risk factors. This suggests that local government officials have a responsibility for better control of air pollution and health care providers need to advise pregnant females about the risks of air pollution during pregnancy.

Keywords: Birth cohort; Complementary log–log-link; Indirect effects; Parallel coordinates plot; Prenatal exposure.

Fig. 1

Study area of MACE birth cohort, showing the location of the study areas (north/south Durban) within the city; Dots represent study participant households from Mitku et al. [36]

Fig. 2

Parallel coordinates plot for trends of (A) low birthweight (B) small for gestational age (SGA) (C) preterm birth (PB) across maternal exposure to PM_2.5, SO₂ and NOx air pollution and other factors

Fig. 3

Correlation among measures of exposure to air pollution

Fig. 4

GSEM predicting adverse birth outcomes (LBW, SGA and PB) among infants from MACE birth cohort. Significant relationships bolded. (Passive smoking (PSmoker), Primary or less maternal education (PLEduc), Maternal Unemployment (Unemp), Low maternal annual income (LInc), Low socio-economic housing (LSEH), Physical exercise (PhyEx))