Nowadays, blood stem cells are basically extracted from blood. Regardless of whether it is bone marrow extraction or blood extraction of stem cells, there is a certain impact on the human body, but generally more mild, absolutely will not affect the normal work and study, compared to saving a life, these effects are nothing, most of the adverse reactions are caused by the drugs in the donation process.

Rationally it should not affect height, but there is no data to support or negate this.

Because you have to be at least 18 years old to register as a donor, and if you find a patient who is a successful match, it's often a long time after that, long past the developmental stage.