Zheng He's fleet to the West did not allow young women to be taken, not because Zheng He was a eunuch who could not use women, but for several other reasons. As for Zheng He's fleet, there were a group of elderly women, and there was a reason for this, they set sail with a special mission.

Zheng He went to the West 7 times, including 6 times during the Yongle year and 1 time during the Xuande year. Taking Zheng He's fourth voyage to the West as an example, this voyage was more than 100 boats, and the entourage was as many as 27,000 people, which may surprise many people. Let's look at who these 27,000 or so people are.
There were nearly 900 officials at all levels, including a number of eunuchs; more than 500 officers in the command and envoys and hundred households; nearly 200 medical officers; scribes, translators, and so on. The accompanying soldiers were as many as 26,800 people.
Of course, there are also some rough people who do rough work, cooks, sailors, etc. There is also a group of old women, for reasons that will be discussed below.
There were two main reasons why Zheng He's fleet did not bring young women.
The captain of the ship sailed at sea, and the wind and humidity at sea were also heavy, and it was not suitable for women to accompany them. Moreover, young women also have problems such as menstrual periods, and it is very inconvenient to accompany them.
There were more than twenty thousand men on the fleet at the time, and if a group of young women were to accompany them for a long time, something unforeseen could happen. At worst, it may cause a riot and the survival of the fleet is at stake.
So why bring a bunch of old women?
On the one hand, the old women can avoid the problems caused by the young women; on the other hand, these old women know how to embroider and deliver babies, and can sew clothes for the people on the fleet during the voyage, and so on, and can also spread embroidery, delivery and other techniques in various countries along the way.