Antenatal tobacco smoke exposure: impact on infant birth outcomes and lower respiratory tract infection in a South African birth cohort
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University of Cape Town and MRC unit on child and adolescent health, Paediatrics and Child Health, South Africa
Stellenbosch University, Paediatrics and Child Health, South Africa
Publication date: 2018-03-01
Tob. Induc. Dis. 2018;16(Suppl 1):A494
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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.

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.

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)].

VariableWfA Z-score (regression co-efficients)WfA Z-score (regression co-efficients)Low birth weight (OR)Low birth weight (OR)Small for Gestational age (OR)Small for Gestational age (OR)LRTI (IRR)LRTI (IRR)
Antepartum smokingCrudeAdjustedCrudeAdjustedCrudeAdjustedCrudeAdjusted
Active-0.44 (-0.62 - 0.26)-0.32 (-0.53 - -0.10)1.91 (1.21 - 3.05)1.40 (0.80 -2.47)1.83 (1.28 - 2.63)1.71 (1.11 - 2.64)1.40 (1.16 - 1.69)1.56 (1.25 - 1.93)
Passive-0.01 (-0.18 - 0.16)0.05 (-0.13 - 0.23)1.13 (0.71 - 1.80)1.05 (0.63 - 1.75)0.80 (0.55 - 1.16)0.79 (0.53 - 1.17)1.09 (0.91 - 1.32)1.11 (0.91 - 1.35)
[Tobacco smoke exposure, birth outcomes and LRTI]

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.
Funding: Bill & Melinda Gates Foundation (OPP1017641), Discovery Foundation, South African Thoracic Society AstraZeneca Respiratory Fellowship, CIDRI Clinical Fellowship, Medical Research Council, South Africa, National Research Foundation, South Africa