Aldous Huxley's title comes from a line of Shakespeare's Tempest, spoken by Miranda when she first sees Alonso:   

O wonder!

How many goodly creatures are here!

How beauteous mankind is! O brave new world!

That has such people in't (5.5.65)

The line "O brave new world" is also what John the Savage says when he first sees Lenina.  Of course, the irony is that while they are superficially perfect, and human feelings and desires are controlled through designed births, there are several flaws to the society of the New World. In the effort to control births, the Bokanovsky Process is used, with sleep conditioning used to develop uniform attitudes, etc., but still people feel stirrings of discontent and emptiness that have to be satiated artificially with soma and pseudo-pregnancies.

In this book, people are not born, they are "decanted" because they gestate in bottles rather than in their mothers' wombs.

The reason for this is that the society wants people to be as uniform as possible.  As much as possible, this means that people are cloned through the Bokanovsky Process.  This also means that they are exposed to exactly the same conditions as they (the fetuses) develop.

This is supposed to give them all (everyone in a given caste) pretty much the same amount of intelligence, the same physical size, etc.