A two-year study of 25,000 babies has found that a lack of folic acid, essential for neural tube formation, was the main cause of birth defects in China's Shanxi Province.

Ren Aiguo, professor of the Reproductive Health Institute of Peking University, said insufficient folic acid caused serious neural tube abnormality, the most common type of birth defect in the coal-rich region in north China.

It could lead to serious brain problems or recessive cleft spine that may cause paralysis, leg deformities or learning difficulties.

During 2003 and 2004, the folic acid level of Shanxi people was around one quarter that of people in Wuxi, Jiangsu Province in east China, Ren said.

Wuxi was an example of the low level of birth defects in south and east China.

With a diet high in noodles and other cooked wheaten food, Shanxi people, especially those in the rural areas, consumed fewer vegetables and meat, the main sources of folic acid, than those in southern China.

However, Reuters released a feature story on June 23, which quoted Pan Xiaochuan, "a professor from Peking University's Occupational and Environmental health department," as blaming a high number of birth defects in the region mainly on environmental pollution, particularly coal mining and burning.

"There has been no scientific evidence confirming such claims in the world so far," said Ren.

Pan Xiaochuan, the only professional source Reuters cited in its report, told Xinhua Monday, "There was no evidence verifying that environmental pollution caused by coal-burning directly led to the high number of birth defects in Shanxi."

Pan, a professor with the Public Health College of Peking University, had said, according to Reuters, "The fact that the rate of birth defects in Shanxi is higher is related to environmental pollution caused by the high level of energy production and burning of coal."

Shanxi reported about 102 in every 10,000 newborns having neural tube problems in 1997, which was four times the national average.

The rate dropped to almost 20 in every 10,000 babies in 2008, twice the national average, an apparent result of government distribution of folic acid tablets to mothers-to-be, according to the provincial health administration.

The Ministry of Health announced in June that it will provide free folic acid supplements as of the end of year for 12 million rural women of child-bearing age, to help prevent birth defects.

China, particularly in rural areas, has always been severely affected by birth deformities, including neural tube defects, congenital heart disease, cleft lip and hydrocephalus, which afflict about 1.2 million Chinese newborns each year.