The rebirthing movement was founded by Leonard Orr in the 1970s. Orr, a former student of spiritual and metaphysical thought with the est organization (Erhard Seminar Training), describes rebirthing as a process of "learning to breath energy as well as air."

The aim of rebirthing is to more fully understand and resolve the issues in one's life and relationships. In essence, it is a program employing techniques of environmental and interpersonal manipulation designed to change behavioural patterns by adopting alternative behaviours. Essentially it consists of continuous deep breathing exercises without pausing between breaths, followed by a massage while on a mattress, called a "dry" birth, or in a tub of oil, called a "wet" birth. During the physiological state that ensues from the hyperventilating, dramatic impressions of happenings in one's childhood are recalled usually resulting in a burst of anger or a flood of tears and a feeling of emotional release. It's a popular New Age fad and an unpleasant experience. The session is interpreted as being a return to the womb.

The theory of rebirthing is simple fantasy, the idea that a new-born brain is able to encode any sort of experience is akin to a blind artist trying to paint a picture without a brush or paints. It is similar in many respects to the hypothesis common to all therapies that seek to "unblock" emotions, and like so many New Age beliefs, remain in the absence of any evidence, simply a fabrication of the imagination.

What it does in fact, is to set up an artificially intense experience in which many people feel release. The same physiological effect (and considerably cheaper) can be achieved by blowing up balloons until you feel giddy.
 

Bibliography:

Adamedes, M. 1983. "Rebirthing – what is it?" Southern Crossings. 3(4).
Duty, N. 1983. Healers, Quacks or Mystics? Hale & Iremonger. Sydney.
Orr, L. 1983. Rebirthing in the New Age. Millbrae. CA.
Kastner, Mark and Burroughs, Hugh. 1993. Alternative Healing. Halcyon Publishing. La Mesa, California.