TIANJIN, Feb. 14 -- Tianjin Municipality on Friday relaxed the one-child policy, allowing couples to have a second child if either of the parents is an only child.

An amendment to the Tianjin Population and Family Planning Regulations was approved at a meeting of the Standing Committee of the Tianjin People's Congress, said Zhang Lijuan, director of the municipality's family planning commission.

Zhang predicts there will be between 10,000 and 20,000 more newborns annually in the following three years. Most of them will be born in the urban area.

Tianjin is the country's fourth city to relax the policy, following east China's Zhejiang, Jiangxi and Anhui provinces.

Relaxation of the rule is a significant change to the country's family-planning policy that has been in effect for more than three decades. The move is part of a plan to raise fertility rates and ease the financial burden on China's rapidly ageing population.

Provincial-level governments in Beijing, Guangxi, Hubei and Jiangsu have announced their intentions to relax the policy in March. Others, including Hunan, Qinghai and Shanghai, promised changes in the first half of the year.