Han says he has attended many urology conferences organized by the Chinese Anti-Cancer Association and Chinese Medical Doctor Association and says he has never seen fertility preservation being discussed. In the absence of this apparent professional ignorance, it may be public education that holds the key, he says.

"What would really make an impact is if patients themselves raised the question. If they were aware enough to ask, 'Will I be able to have a baby after this?' the doctor would certainly pay attention."

Xing Liu, a researcher in the institute of reproduction and stem cell engineering of Central South University in Changsha presents a more positive picture of professionals carrying out their duties to inform. In research on the Hunan sperm bank's 149 sperm preservation clients she found that 80 percent of them had learnt about fertility preservation from their doctors.

Another black hole on the issue of sperm preservation relates to people in occupations whose working conditions make them particularly susceptible to being rendered infertile.

Apart from soldiers this group includes firefighters, sailors, radiologists and many others exposed to environmental toxins such as chemicals, herbicides and pesticides.

Yet it seems that in China few people are fully aware of the physical dangers their jobs expose them to.

Lu Guangxiu says many of her patients are radiologists who find that their partners' embryos are deformed then consult her seeking help.

"All I can tell them is that it's too late and that they ought to have come to me earlier. Before embarking on their profession, they should have stored their sperm, but they had no idea."

She has suggested to the leaders of many companies that the best benefit they could possibly offer their employees is the preservation of their eggs and sperm. Last year NBC News in the US reported that technology companies Apple and Facebook were offering to pay the fees for any of their female employees to preserve their eggs. Lu says such a scheme could work in China.

In the Guangdong sperm bank, high-risk professionals account for just one percent of the several hundred fertility preservers, and cancer patients account for more than 90 percent, says its director, Zhang Xinzong.

In Jiangxi, the situation is similar. No more than 100 men preserved their sperm as long-term insurance, among whom fewer than 10 percent are in risky occupations. Jiang Xianglong, director of Jiangxi's sperm bank, says that he has even halved its storage fee to 1500 yuan ($230) a year to attract more clients. A similar service offered by the California Cryobank, a national US sperm bank established in 1977, costs $475 a year.

Fan Liqing, vice-president of Reproductive and Genetic Hospital of CITIC-Xiangya, says the partners of 60 percent of his infertile patients have had abortions, and Fan encourages all men to at least consider their options early on.

"For healthy men who want to have babies between 20 and 25, there is no need to store their sperm. But if they do not plan to produce babies at that stage, I recommend that they take steps to preserve their fertility as soon as possible."