Supporters of change say an adjusted policy in pilot areas will help avoid a possible birth peak in the event of a blanket policy change.

But Yuan said: "Even a nationwide change won't have a major impact on population development.

"In central and western China, or in the countryside, the impact of a relaxed policy could be quite limited because of a relatively low proportion of single children."

There are more than 140 million single children across the mainland, mostly in large cities such as Beijing, Shanghai and Tianjin, the coastal provinces of Jiangsu and Zhejiang as well as northeastern areas, statistics from the commission show.

"So an eased policy will not compromise the nation's long-term goal of achieving low population growth," Yuan said.

Internationally, a fertility rate — the average number of children a woman has — of 2.1 is considered necessary to replace or renew the population. The rate in China stands at 1.6.

Experts say that with an eased policy the figure might rise to between 1.7 and 1.8, still a relatively low level for population growth.

Gu Baochang, a professor at the Population and Development Studies Center at Renmin University of China, said smaller families are a universal trend in socio-economic development.

A regional study conducted by his team between 2006 and 2010 found that 70 percent of rural families in Jiangsu province have single children.

As they entered childbearing age, of the 4,284 women surveyed who were eligible for a second child, under 10 percent chose to increase the size of their families.

Gu said, "Family planning policy is no longer the key factor determining people's reproduction choices."

Yuan said a policy change will help solve demographic problems such as an aging population and skewed gender ratio.

In 2012, the gender ratio at birth in China stood at 117.7 — 117.7 boys for every 100 girls — far higher than a global figure of between 105 and 107, according to the National Bureau of Statistics.