Association between biomass fuel use and maternal report of child size at birth--an analysis of 2005-06 India Demographic Health Survey data

BACKGROUND: Observational epidemiological studies and a systematic review have consistently shown an association between maternal exposure to biomass smoke and reduced birth weight. Our aim was to further test this hypothesis.
METHODS: We analysed the data from 47,139 most recent singleton births during preceding five years of 2005-06 India Demographic Health Survey (DHS). Information about birth weight from child health card and/or mothers' recall) was analysed. Since birth weight was not recorded for nearly 60% of the reported births, maternal self-report of child's size at birth was used as a proxy. Fuel type was classified as high pollution fuels (wood, straw, animal dung, and crop residues kerosene, coal and charcoal), and low pollution fuels (electricity, liquid petroleum gas (LPG), natural gas and biogas). Univariate and multivariable logistic regression models were developed using SURVEYLOGISTIC procedure in SAS system. We used three logistic regression models in which child factors, maternal factors and demographic factors were added step-by-step to the main exposure variable. Adjusted Odds Ratios (AORs) and their 95% CI were calculated. A p-value less than 0.05 was considered as significant.
RESULTS: Child's birth weight was available for only 19,270 (41%) births; 3113 from health card and 16,157 from mothers' recall. For available data, mean birth weight was 2846.5 grams (SD = 684.6). Children born in households using high pollution fuels were 73 grams lighter than those born in households using low pollution fuels (mean birth weight 2883.8 grams versus 2810.7 grams, p < 0.001). Use of biomass fuels was associated with size at birth. Unadjusted OR was 1.41 (95% CI, 1.27 1.55). Adjusted OR after controlling for child factors was 1.41 (95% CI 1.29, 1.57). AOR after controlling for both child and maternal factors was 1.21 (95% CI 1.06, 1.32). In final model AOR was 1.07 (95% 0.94, 1.22) after controlling for child, maternal and demographic factors. Gender, birth order, mother's BMI, haemoglobin level and education were significant in all three models.
CONCLUSIONS: Use of biomass fuels is associated with child size at birth. Future studies should investigate this association using more direct methods for measurement of exposure to smoke emitted from biomass fuels and birth weight.