Biomass and kerosene cook stoves are not too familiar to the everyday American, but in developing countries, they are usually the only types of stove appliance residents have access to. Unfortunately, they can have harmful effects on the user’s cardiovascular health, particularly that of pregnant women, according to a new study by researchers at the University of Chicago.

Their study, published online, ahead of print in the American Thoracic Society’s American Journal of Respiratory and Critical Care Medicine, found that the frequency of developing hypertension and diastolic blood pressure were lowered in pregnant women when they cooked with ethanol, rather than with wood or kerosene.

"Although previous studies found that exposure to household air pollution increased the risk of adverse pregnancy outcomes, no randomized, controlled trial had investigated whether clean-burning fuel would reduce the incidence of hypertension in pregnant women," said lead study author Christopher O. Olopade, MD, professor of medicine and family director of international programs at the University of Chicago's Pritzker School of Medicine, in a statement.

Olopade and his team examined more than 300 pregnant women living in Ibadan, Nigeria. The cohort excluded women who smoked, lived with a smoker, cooked for a living or already were diagnosed with hypertension.

Half of the women who usually cooked with firewood or kerosene were randomly assigned to begin using ethanol. The other half continued to cook with wood and kerosene. The researchers then measured their blood pressure over six patient visits.

Results showed that 6.4 percent of the women cooking with wood or kerosene developed hypertension compared with the 1.9 percent of those cooking with ethanol. Among women cooking with wood or kerosene, their mean diastolic blood pressure was 2.8 mmHg higher than those cooking with ethanol.

The findings coincide with the decision by the World Health Organization to remove kerosene as a home cooking and heating fuel, Olopade said.

"The results of our study add to the evidence that vulnerable populations, especially pregnant women, would gain important health benefits from stoves that burn clean fuels," he said. "Additional studies are still needed to determine how much of a reduction in exposure levels will result in significant and sustained health benefits."