SHANGHAI, Feb. 2 -- Shanghai's legislature on Tuesday passed an amendment to relax the city's birth control policy, becoming the sixth region nationwide to allow couples to have a second child if either parent is an only child.

The amendment, passed at a meeting of the Standing Committee of the Shanghai Municipal People's Congress, will go into effect on March 1, the local legislature said in a statement.

Shanghai now faces a spate of demographic challenges, including a low birth rate, an aging population and an unbalanced population structure, according to the Shanghai Municipal Commission of Health and Family Planning.

Similar reasons were cited when the Third Plenary Session of the 18th Communist Party of China Central Committee decided to loosen the decades-old one-child policy last November.

About 75,000 to 150,000 newborn babies are estimated to be added to the city's population in the next three to five years, said the Shanghai Municipal Commission of Health and Family Planning.

Currently about 370,000 families in Shanghai are eligible for the eased policy.

Xue Mingyang, head of the Committee of Education, Science, Culture and Health under the Shanghai Municipal People's Congress, said the authorities will seek to provide better health and education services to cope with the rise in newborns.

In addition to Shanghai, the regions of Beijing Municipality, Tianjin Municipality, Zhejiang Province, Jiangxi Province and Anhui Province have also already changed their policies.