Safety of Rebirthing
Rebirthing - as taught to genuine practitioners, is a completely safe and healthy process.
Unfortunately, there are some who have falsely used the word 'rebirthing' to falsely refer to completely different techniques, for example, 'attachment therapy' as happened in a high-profile tragic case in 2001 in Colorado.
Rebirthing in its pure form is a technique of enhanced breathing, relaxation and disciplined awareness, comparable to breathwork-based (or prana) yogas of the east. As such, it can only be healthy. It's when people stop breathing that they tend to have problems.
If you are at all concerned about the authenticity of what your practitioner is offering, feel free to ask him/her about the lineage of his/her training - who was his/her trainer, and who was their trainer, and so on. The lineage should reach the original 12 rebirthers as listed in the textbook Rebirthing in the New Age by Leonard Orr and Sondra Ray (Amazon link).
Please know that all the rebirthing practitioners listed on this site practise authentic rebirthing, and have a training lineage to these original 12 rebirthers.