Antenatal environmental exposure to indoor air pollution and environmental tobacco smoke: association with birth outcomes in an African birth cohort.

UNLABELLED: Indoor air pollution (IAP) and environmental tobacco smoke exposure (ETS) are important antenatal environmental exposures that may adversely impact birth outcomes.

OBJECTIVES: To investigate the impact of IAP and ETS during pregnancy on birth outcomes including respiratory distress in an African birth cohort, the Drakenstein Child Health Study.

SETTING: Prospective cohort study conducted in a periurban setting in sub-Saharan Africa within a large birth cohort.

PARTICIPANTS: Consenting pregnant women (n=1137) enrolled between 20 and 28 weeks' gestation, with 1143 live births included in the analysis. Participants were recruited antenatally, with inclusion based on residency in the study area and availability of exposure and outcome data.

PRIMARY AND SECONDARY OUTCOME MEASURES: Primary exposures included antenatal IAP (particulate matter (PM10), carbon monoxide (CO), nitrogen dioxide, sulphur dioxide, volatile organic compounds) and ETS (maternal urine cotinine). Outcomes included birth anthropometry, prematurity, low birth weight and neonatal respiratory distress.

RESULTS: Among 1143 live births, 17% were premature, 15% had low birth weight and 7% had respiratory distress. Maternal active smoking was associated with reduced weight-for-age z-scores (WfAz; β -0.54; p<0.001). Babies exposed to PM10 above ambient standards were 1.88 times more likely to experience respiratory distress compared with those with exposure below ambient standards (p=0.058). Similarly, exposure to CO above ambient standards was associated with a trend towards a doubled odds of respiratory distress in babies at birth (OR: 2.19 (0.97 to 4.98); p=0.061).

CONCLUSIONS: Antenatal exposure to IAP and ETS is associated with adverse birth outcomes, including impaired growth and increased risk of respiratory distress. These findings support the need for targeted public health interventions to reduce exposure during pregnancy and highlight the importance of improving air quality to mitigate long-term respiratory health risks.