Beijing: Mengmeng was only a month old when his parents started hunting for a bride for him. The Zhangs made sure they put friends with newborn daughters on the guest list for the party to mark that milestone in August last year.

Experts estimate that China's growing gender gap will leave 24 million men without mates by 2020, and the couple are already worried it will be hard for Mengmeng to find a wife when he grows up.

'Nowadays, it's so competitive, parents have to prepare early to give their child a head start, be it finding a good school or a mate,' said Mrs Zhang, 30, a finance professional who declined to give her full name.

China's one-child policy, and the traditional preference of parents for males, have combined to produce a high rate of sex-selective abortions.

The normal male-female ratio should be between 103 and 107 males for every 100 females. By the early 1980s, there were 108 boys born for every 100 girls, and by 2000, this had risen to 116 boys for every 100 girls, and as many as 140 in parts of the countryside.

As a result, China will face a surplus of 24 million bachelors, known here as 'bare branches' (guanggun), by the end of this decade, according to a recent study by a leading think-tank, the Chinese Academy of Social Sciences.

Mr Li Wenjie, whose son Chenghong will turn 22 by then, said that is 'a very scary prospect'.

'But what's the point of worrying?' said the 39-year-old civil servant who lives in north-east China. 'He'll just have to try his luck.'

The Zhangs are better off and that may boost Mengmeng's chances. While the couple have not made a deal with potential parents-in-law, they noted that some families are 'open to the idea'.

Mrs Zhang admitted that their actions looked like a return to the traditional Chinese practice of matchmaking children at birth. But she said: 'We're not going to force the children to marry at a certain age. We'd just encourage it.'

The People's Daily noted in a recent article that some Chinese may find themselves taking foreign brides, or marrying either much younger or older women.

But Mr Li said: 'I would still want my son to marry a Chinese girl whose age difference is not more than three years.'

Mr Qiu Sheng, 39, meanwhile, has other concerns for his 13-year-old daughter.

'I'm happy that she will have more choices (for a mate) next time, but also fearful for her safety,' said the masseur, who plans to teach his only daughter self- defence.

China has already seen a growing number of crimes against women such as kidnapping and rape.

Experts like Dr Therese Hesketh of the London-based UCL Centre for International Health and Development have linked this to a surplus of men under age 20.

'If you've got highly sexed young men, there is a concern that they will all get together and, with high levels of testosterone, there may be a real risk that they will go out and commit crimes,' she told the Associated Press.

Some wonder if this growing social threat of social instability may force the government to revoke its 30-year-old one-child policy.

But population expert Li Xiaoping of the Chinese Academy of Social Sciences said that having more children would not address the imbalance.

'The key is to impose much heavier punishments to curb all abortions of baby girls,' he said.

Chinese society's strong bias for males is obvious.

As Mrs Zhang said: 'Any amount of trouble to find my son a potential wife is worth it because we have an heir to carry the family name.'

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Additional reporting by Lina Miao

This article was first published in The Sunday Times.