China has a rule that all its space-going astronauts, male and female, must be married. The logic behind this — specifically for women — was explained in a March Time Magazine article:
The reasoning behind the prerequisite, according to officials, is that spaceflight could potentially harm the women's fertility. "It's out of the consideration of being responsible for the female pilots," Xu Xianrong, director of the PLA's Clinical Aerospace Medicine Center in Beijing and a member of the selection panel, told the official government news agency Xinhua. "Though there is little evidence on how the space experience will affect the female constitution, we have to be extra cautious, because this is a first for China." Ensuring that the female astronauts have already reproduced, he said, will guarantee that their family planning is not disrupted. But at least one authority, Zhang Jianqi, former deputy commander of the country's manned space program, has stated that the requirement stands because married women are more physically and psychologically mature.
Why does China require that its astronauts be married? [CS Monitor]
