Efforts to relax China's family planning policy have reached a milestone. Henan, the country's most populous province, has fallen into line with the rest of the mainland by allowing couples a second child if both parents are only children.

Many experts say this is a move to counter the rapid ageing of the population. But there are concerns over how to support a baby boom amid limited resources.

Henan is taking the last step to fill in the national gap in the family planning change. On Friday, the provincial law makers passed the policy adjustment. The move comes more than 20 years after Shanghai became the first mainland jurisdiction to do so.

The authorities in Henan say the family planning policy has prevented more than 33 million births since it was introduced 3 decades ago.

Wang Feng, the Director of the Brookings-Tsinghua Centre for Public Policy, believes the policy should be here to stay and said, "Many people in China still feel that we have too many people. And we do not believe that fertility is already so low, and still believe that the one-child policy has created such a tremendous benefit for China that it should be continued. So, in China we have not seen any real signs of policy change, which will not be in China's interest."

However, many local governments have loosened the policy since 1990s. Farming provinces like Henan will need younger populations to focus on boosting productivity in labour-intensive agriculture.

With most of its young living and working in cities of coastal provinces as migrant workers, the ageing population is a critical issue. Experts predict that the lack of young people of working age will peak in 2015 and then fall, denting China's economic growth in the coming years.

Wang Feng, the Director of the Brookings-Tsinghua Centre for Public Policy, said "Clearly the pressure for housing, for jobs, and for education, for daycare, they all create pressures for young people to think about marriage and to think of having children, let alone having two or three children, or even one child."

To name just a few on the list of social problems partly caused by huge population.The family planning policy can only reduce the number of births, but it can't solve all the problems.