By Farah Master and Laurie Chen

HONG KONG/BEIJING (Reuters) - Mary Meng is so busy and stressed working for a Chinese tech company in Shanghai that she can't imagine having a second child.

"The work pressure is such that you don't even have any time to spend with your child," said the 37-year-old mother of a primary school-aged boy. "How can I think about taking care of two children? I have no idea."

That resonates with urban residents anywhere. But given the pace of population decline and ageing in China, the impact of the fast-paced, expensive city life on birth rates should be treated with more urgency by Beijing, demographers say.

China is rapidly running out of mothers. The number of women of reproductive age, defined by the United Nations as 15-to-49, is set to drop by more than two-thirds to under 100 million by the end of the century.

At a twice-a-decade top political gathering last month, China announced plans to build a "birth-friendly society" - pledging to implement measures long-called for by population experts, such as lowering childcare and education costs.

But, to the despair of the same experts, Beijing also vowed to encourage more people into urban areas.

This policy aims to increase housing demand to prop up the crisis-hit property sector, and revive flagging economic growth through productivity gains and stronger consumption. Urban residents typically produce and buy higher value-added goods and services than their rural counterparts.

But the fresh urbanisation push overlooks basic demographic theory. In the cities, people have fewer children due to high housing costs, limited space, expensive education, and because they spend most of their day at work.

Couple infertility rates in China have also risen from 2% in the 1980s to 18%, versus around 15% globally - with doctors blaming the rise on factors such as stress related to urban jobs and industrial pollution.

Fertility rates in China's rural areas are slightly higher at 1.54 versus the national average of 1.3 in 2020, according to the latest breakdown from China's top economic planner, while Shanghai's fertility rate in 2023 was 0.6 versus 1.1 nationally.

Authorities are "foolishly" driving young people "to the most birth-unfriendly big cities, which will lead to a continued decline in fertility and exacerbate the ageing crisis," said Yi Fuxian, a demographer at the University of Wisconsin-Madison.

"The suppression of fertility rates by population density is a biological law."

This phenomenon has been most evident in east Asia. Japan, South Korea and Taiwan urbanised and industrialised at a faster pace than most other economies post-World War Two. They also have the lowest fertility rates globally.

While China's birth rates are also very low after decades of a strict one-child policy, not all is lost.

At 65%, its urbanisation rate is lower than the 80-90% rates in Japan or South Korea - and this could give it room for manoeuvre, demographers say.

Improving rural living standards by providing better public services or liberalising land rights would have a more sustainable impact on economic growth than continuing urbanisation as they could improve birth rates, they say.

"The population size is always a multiplier" in the economy, said Samir KC, professor at the Asian Demographic Research Institute at Shanghai University.

'JUST SURVIVAL'

To have a stable population, countries need fertility rates of 2.1. That means that for every woman like Meng, who only raises one child, another would need to have three.

Poppy Yu, 21, who works at film production company in Beijing six or seven days a week, wants none.

"I don’t have the money or energy," Yu said.

China's "birth-friendly society" vision entails bringing down costs of parenting and education, lengthening parental leave, upgrading maternity and paediatric care and boosting child subsidies and tax deductions.

Many countries offer such incentives. But those with successful birth policies - such as France or Sweden - stand out through greater gender equality, stronger labour rights and robust social welfare.

Reducing childcare costs does not work on its own "and instead promotes a certain set of family values that demand that women take domestic responsibilities," said Yun Zhou, demographer at the University of Michigan.

Meng believes no policy would work until Chinese people start hoping again for a better life, financially.

"Now everyone thinks there is no prospect at all," she said. "No matter how hard you work, it is just survival."

($1 = 7.1469 Chinese yuan renminbi)