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)].
Variable WfA 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 smoking Crude Adjusted Crude Adjusted Crude Adjusted Crude Adjusted 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|