Rebirthing-Breathwork
Rebirthing-Breathwork is a form of alternative medicine mainly consisting of a breathing technique.  It shares a common belief with various other therapies called Rebirthing, with both groups believing that human birth is a traumatic event (see birth trauma) and that reviewing or revisiting this event, in some way, can have therapeutic benefits.  However, the techniques used in Rebirthing-breathwork are very different to those used by these therapies.

# History
Rebirthing-Breathwork grew out of the work of Leonard Orr.  The name rebirthing was first used by Orr and his followers to describe the technique and became the subject of the book Rebirthing in the New Age which Orr co-wrote with Sondra Ray. When Orr first started experimenting with these breathing techniques, he noticed that he would often have what he described as memories of his birth. He believed that by reliving his birth experiences through connected breathing, he was in fact healing the trauma of his own birth. Although he was at that time unaware of the practices of kriya yoga and pranayama, Orr further developed the rebirthing process between 1962 and 1974 and discovered for himself that modifications in breathing practice appeared to bring about improvements in health, mental clarity and emotional well-being.
Development of Rebirthing as a therapeutic modality in its own right started in 1974, and has been further developed from that time. Accompanied by fellow researchers, Orr refined it into a system that can be practised in the context of a therapy session and taught to clients over a series of sessions.
Proponents estimate that, since 1974, more than ten million people worldwide have learned the process, with more than one hundred thousand people completing practitioner training.
In Orr's Rebirthing-Breathwork, the main breathing technique is a connected breath, where the breather does not pause between inhale and exhale. According to believers, this causes a build up of oxygen in the blood and a build up of prana or life energy. Breathing sessions are done lying down and usually last one to two hours.

# Beliefs
The assumptions behind rebirthing is that human birth is traumatic, due to ignorance and misunderstanding on the part of most medical professionals (and parents/family) and that humans never forget their birth, they just repress the memory.  Rebirthing-breathwork practitioners believe that in addition to cerebral memory (based in the brain), humans also possess cellular memory, which is distributed amongst the body's cells, tissues, organs etc.
They believe that the trauma suffered during birth, and the specific nature of this trauma, has a deep effect on one's psyche and shapes one's perception and experience of life, self and the world in ways of which one is mostly unaware (For instance, someone born by forceps delivery might rely on others to pull them out of destructive situations.)  Practitioners believe it is possible to gain recall of aspects of birth, gestation and early childhood and to release the accompanying emotions; such release can generate a positive paradigm shift and life transformation based on a change in the experiences they believe one subconsciously attracts.
Rebirthing-breathwork teachings state that it can increase in the client or solo practitioner's human potential, inner peace and mental clarity.  The practitioner can manage the challenges of life more easily.  Believers say those who practice rebirthing-breathwork can gain greater insight into the human condition and the purpose of their existence; a greater sense of their personal relevance to the world.
Human breathing, practitioners say, is almost universally inadequate; virtually all people are suppressing large amounts of emotional, physical and mental "tensions", and require relatively high levels of CO2 in their blood in order to keep these tensions suppressed.  They feel that the major causes of all human illness are these accumulated tensions; the practice of rebirthing-breathwork techniques they believe can detoxify the system and release such tensions.  They profess that this can cause physiological transformation, to the point where prevention or permanent spontaneous remission from illness becomes possible.
Practitioners feel rebirthing provides a direct, replicatable, physical experience of Divine Love through the saturation of the body with prana.
The philosophies which accompany Rebirthing appear to be a loose, intuitive mix of western metaphysics, gnosticism, hinduism, buddhism,  and (what some may argue to be) original Christian teaching. Early  writings of Orr and Sondra Ray expressed belief in Immortalism.

# Criticisms
While it is clear that prenatal events can have an influence on the subsequent development and life of the child through developmental or hormonal factors, and there can be physical complications of birth, there is little scientific support for the claim that the birth process is inherently psychologically "traumatic". Studies comparing children born by caesarian section to those born through the birth canal have not found statistically significant differences.
Scientific evidence to support the idea of cellular or other "non-cerebral" memory is not widely acknowledged, although believers in such theories have presented cases some find convincing.
There is no scientific evidence that any birth memories can be recovered.  In fact, the available research strongly indicates that the human brain is unable to form conscious memories until approximately the age of two.  There is, however, strong evidence that false memories can be planted (either inadvertently or deliberately), as in false memory syndrome.
There is little consensus for the position that normal breathing in a healthy human is inadequate and no evidence that maintaining high levels of O2 has any effect on the suppression of tension.  High levels of end tidal CO2 which is a result of insufficient respiration may have been linked to hypertension and elevated anxiety, but far from reducing anxiety, hyperventilation, a form of over-breathing, is a symptom of panic attacks or lack of relaxation.
- Currently no well-controlled studies demonstrate the effectiveness of the technique, but there is psychotherapy research underway at the University of Queensland School of Medicine, evaluating the effectiveness of Breathwork in treating depression and anxiety.
- An unrelated technique, also named "rebirthing", sharing some beliefs but developed decades after Orr's work, resulted in the death of Candace Newmaker.

# Unrelated techniques also called rebirthing
Other largely unrelated therapies which are sometimes called Rebirthing also go by the names compression therapy, cuddle time and holding-nurturing process.  Rebirthing is considered by such practitioners to be an appropriate strategy for treatment of attachment disorder.
The term "Rebirthing" drew unfavorable attention in 2001 when several therapists using techniques strongly opposed by most rebirthing-breathwork practitioners, were sentenced to 16 years in prison for suffocating a 10-year-old Colorado girl during a 'rebirthing' session that was part of a two week attachment therapy intensive. Among other techniques, the session involved wrapping the girl in a sheet and having adults sit on her to simulate contractions and motivate the girl to "emerge from the womb".
Rebirthing-breathwork is not this form of 'rebirthing,' which is sometimes used as part of Attachment therapy.  Under Candace's Law, this practice was outlawed in the state of Colorado. . 
Practitioner's of Leonard Orr's rebirthing now often use the suffix breathwork, naming their technique rebirthing-breathwork, to differentiate themselves from these other therapies.