Antenatal tobacco smoke exposure: impact on infant birth outcomes and lower respiratory tract infection in a South African birth cohort

Abstract

Background: The impact of antenatal tobacco smoke exposure, on child health outcomes has not been well studied in African children. This study investigated the prevalence of antenatal tobacco smoke exposure and the associations with infant birth outcomes and lower respiratory tract infection (LRTI) in the Drakenstein Child Health Study (DCHS), a South African birth cohort. Methods: Consenting pregnant women were enrolled antenatally and mother-infant pairs followed from birth through the first year of life. Self-reported questionnaires assessed maternal and household smoking and maternal urine cotinine collected antenatally and at birth was measured. Birth outcomes including weight-for-age (WfA) z scores, low birth weight (LBW) and small for gestational age (SGA) were recorded. LRTI defined using WHO criteria was documented by trained study staff during the first year of life. Linear (WfA z-score), logistic (LBW, SGA) and Poisson (LRTI) regressions were used to investigate associations with tobacco smoke exposure. Results: 1137 women were enrolled with 1143 live births. Urine cotinine measures classified 352/1093 (32%) as active and 479/1093 (44%) as passive smokers. Median birth weight was 3,085 (IQR2,710 - 3,420) kg; 524 episodes of LRTI occurred. Infants of active smokers had a 0.32 (95%CI 0.10 - 0.53) lower WfA z score and almost doubled risk of being SGA [OR 1.71 (95%CI 1.11 - 2.64)]. Maternal smoking was associated with an increased risk of LRTI [IR 1.56 (95%CI1.25 - 1.93)]. Conclusions: There was a high prevalence of antenatal maternal smoking and tobacco smoke exposure which significantly impacted on infant birth outcomes and LRTI incidence in infants. Urgent and effective interventions to reduce antenatal tobacco smoke exposure are required to improve child health. (Table presented).