In short due to Mao's pro-natalist policies starting in the late 50s till mid 70s. The pro-natal policies were then reversed after Mao's death resulting in the one child policy to curb excessive population growth.

Domestically, People's Republic of China conducted her first census in 1953, the result show the population of China then was 601 million with an annual population growth estimated at 0.2 %. (Total world population back then was around 3,000 million.) Initially, in 1957 February during the 11th Supreme Council of State meeting (involves the highest ranking officials, like a cabinet meeting), due to the necessities of planned economy under constrained resources, population control was gaining favor. But the following month, due to grossly over reported production yields, Mao made the remark, "based on the production yields, we can afford to have a few hundred million more people", signally a change in population policy. Together with the starting of the Great Leap Forward, population growth was considered to be a part of the country's transition from agricultural to industrial society - more workers, more production. Resulting from the policy is that the family with more children are given more resources, strongly encouraging child rearing.

Internationally, post Stalin's death in 1953, Soviet-Sino relationship deteriorated very quickly. Post Mao's 1957 visit to Moscow, Mao realized the ideological differences between Khrushchev's Soviet and China. Mao understood the differences will only lead to war and population growth became part of war strategic planning. Mao said, "we have nothing to fear of a nuclear war. China has 600 million people, even if half died we would still have 300 million left." Mao is a huge proponent for "quantity has a quality of its own". In the 1958 publication, "Introducing A Co-operative", Mao was clearly fully in favor of population growth, the entire article is a praise to "more people, more power". Since Mao had a cult of personality, very often Mao's opinion pieces are taken as the official directive of the Chinese government, and pro-natal policies started to form from local levels.

The pro natal policies stemmed from both domestic and foreign influences resulted in about 2% annual population growth from 1960 to 1990, with a slight decrease during the Great Famine years.