Planned birth policy, as it is known in China, first implemented in 1979

Government permission required for having a child

Strongly enforced in urban areas but varies for different locations and ethnic groups

Those in rural areas usually allowed second child if first is a girl or disabled

Ethnic minorities usually allowed to have more children

Penalties for having more than one child usually economic – fines, denial of work bonuses, having to pay for child to go to school and whole family's healthcare,

But officials also reportedly detain family members, destroy houses, sterilise women and conduct forced abortions

Government blames overzealous officials for any inhumane or uncivilised enforcement of the policy

In some cities, couples who are both only children themselves may have two children

China's fertility rate estimated to be between 1.6 and 2 births per woman

Government says 1.3 billion population is 300 million smaller than it would have been without policy