Cooking smoke and tobacco smoke as risk factors for stillbirth.

Smoke from biomass combustion produces some of the same pollutants found in tobacco smoke and ambient air, yet only one study to date has linked cooking with biomass fuels to increased risk of stillbirth. The mechanisms by which biomass smoke may cause stillbirth are through exposure to CO and particulates in biomass smoke. Using information on 19,189 ever-married women aged 40-49 included in India's 1998-99 National Family Health Survey, we examined the association between household use of biomass fuels (wood, dung, and crop residues), tobacco smoke (both active and passive), and risk of stillbirth. Data were analyzed using binary and multinomial logistic regression after controlling for several potentially confounding factors. Results indicate that, with other factors controlled, women who cook with biomass fuels are significantly more likely to have experienced a stillbirth than those who cook with cleaner fuels (OR= 1.44; 95% CI: 1.04, 1.97). Women who cook with biofuels are twice as likely to have experienced two or more stillbirths as those who cook with cleaner fuels (RRR= 2.01; 95% CI: 1.11, 3.62). The adjusted effect of active tobacco smoking is also positive (OR = 1.23) but not statistically significant. No effect of passive smoking was found, nor was there evidence of any modifying effects of tobacco smoking.