China’s major revision to its infamous one-child policy is set to partially take effect in the first quarter of next year, the family-planning commission said late on Monday.

The policy change will first take effect in some areas of China, Yang Wenzhuang, director at the National Health and Family Planning Commission, told Xinhua, the state news agency. The change would allow millions of Chinese families to have two children, the South China Morning Post reported on Tuesday.

The revision was first announced at China’s decisive third plenum meeting, where the leadership issued a road map for the economic and political policy changes it has in mind for the coming decade. The change to the strict one-child policy, which has been in effect for close to three decades, was one of the biggest planned reforms.

Under the new policy, couples, if one of whom is an only child, will be allowed to have two children. Previously, only couples who are both only children were allowed two children.  The government hopes this will help raise fertility rates and ease the financial plummet China faces as its population ages rapidly.

Authorities are now calculating the number of eligible couples and evaluating their situations before specific regulations are approved, Yang said.

Since the policy reform was first announced, many eligible couples are considering having a second child. Stocks of baby-product companies went up, and there was a rush for fertility-boosting products.

China will eventually dispense with family-planning restrictions, first enacted in the early 1980s, following a decade of uncontrolled population surge. But in the near term, the policy will not be abolished altogether, the South China Morning Post reported.