The sight of the partially exposed buttocks of kaidangku-clad children in public places frequently astonishes foreign visitors, who often photograph them.

[5] Frequently babies are held closely by parents, grandparents or other extended family members caring for them, sensitive to when they need to relieve themselves.

[1] Seven years earlier, in her memoir Red China Blues, Chinese Canadian journalist Jan Wong speculates that their use evolved from chronic shortages of cloth, soap and water.

During the later years of Mao Zedong's rule, brightly colored kaidangku on the streets of Beijing offered a sharp contrast to the austere blue and gray tones of adult clothing prescribed by the Cultural Revolution.

[8] Even after the economic liberalizations promoted by Deng Xiaoping in the subsequent decades and the ensuing introduction of more Western culture and ideas, they remained in use for the vast majority of children in the People's Republic of China.

[9] When Wong, then a Chinese correspondent for Toronto's The Globe and Mail, bore a son in Beijing in 1990, only one hotel in the city sold disposable diapers.

Within five years of Pampers' introduction, about $200 million in disposable diapers were being sold in China annually, and many manufacturers reported their sales were growing by double-digit percentages.

The shift in attitudes had drastically reduced the use of open-crotch pants—upscale retailers no longer carried them, and Chinese parenting magazines depicted babies wearing diapers exclusively.

[8] Zhao Zhongxin, an education professor at Beijing Normal University, said open-crotch pants had become an indicator of socioeconomic status in the new China.

A Zhejiang woman who ran a fruit stand in the city told the newspaper that she dressed her son in them only in that weather, since it was more comfortable for him and reduced the risk of diaper rash.

[14] However, parents are cautioned that kaidangku can be dirtier, leading to a higher risk of problems like urethritis, cystitis and other complications of urinary tract infections.

Children in them are also believed to face a higher risk of frostbite in winter, and 163.com warns that boys with easy access to their exposed genitals "can easily develop bad habits.

In addition to the medical, sanitary and environmental drawbacks, it says that they show no respect for the child's privacy and that he may in the future be embarrassed by photographs of himself wearing them, particularly as they become less common.

Many of his patients were men who, as children on farms, suffered serious injury to their organs when they squatted in their open-crotch pants in areas where dogs or pigs ate their own feces and the animals bit the boys' penises in the confusion.

[16] Lastly, in his 1996 memoir The Attic, artist Guanlong Cao recalls an incidental benefit of kaidangku to his parents: When [my sister] Chuen was three years old, she still wore open-crotch pants that revealed two banana-shaped slices of her bottom.

Aggressive advertisers create an impression that consumer products are vastly superior to what mothers have practiced for eons and urge parents to buy what they can barely afford," she wrote.

[18] Around that same time, inspired by the Chinese example, parents in the U.S. and other Western countries began forming "diaper-free" support groups and practicing elimination communication toilet training on younger babies, using the ba whistling sound to incite urination.

[19] Western parents working in China also saw the use of kaidangku up close, and in some cases decided to emulate Chinese methods in toilet training their own children.