Selective abortion in favour of males has left China with 32 million more boys than girls, creating an imbalance that will endure for decades, an investigation released on Friday warned.
The probe provides ammunition for those experts who predict China's obsession with a male heir will sow a bitter fruit as men facing a life of bachelorhood fight for a bride.
"Although some imaginative and extreme solutions have been suggested, nothing can be done now to prevent this imminent generation of excess men," says the paper, published online by the British Medical Journal (BMJ).
In most countries, males slightly outnumber females -- between 103 and 107 male births for every 100 female births.
But in China and other Asian countries, the sex ratio has widened sharply as the traditional preference for boys is reinforced by the availability of cheap ultrasound diagnostics and abortion.
This has enabled Chinese couples to use pregnancy termination to prevent a female birth, a practice that is officially condemned as well as illegal.
In China, an additional factor has been the "one-child" policy.
In general, parents who have a second child are liable to pay a fine and contribute disproportionately towards the child's education.
But in some provinces, a second child is permitted if the first is a girl or if parents are experiencing "hardship." And in a few others, couples are allowed a second child and sometimes a third, regardless of sex.