Zhang Weiqing, minister in charge of the National Population and Family Planning Commission, said that China had baby booms in the early 1950s, 1960s and the late 1980s. The fourth is expected between 2006 and 2010.

China has nearly 100 million people who were raised in single-child families and many of them have approached their child bearing age.

Also the children of rural couples, which have been allowed to have more than one child if their first is a girl since the mid-1980s, will soon starting having babies of their own.

"To maintain the current low birth rate, the family planning policy must not change," he said during an online interview at the government's website. The pending baby boom is not expected to be large and the country hopes to maintain a relatively low birth rate.