(via https://en.wikipedia.org/wiki/Stanislav_Grof )

According to Grof, the reliving of emotional and physical pain can become so intense that an identification with “the pain of entire groups of unfortunate people, all of humanity, or even all of life”,[23] can manifest. This is accompanied with “dramatic physiological manifestations”.[23]

At this level, death may be encountered and birth relived.[24] According to Grof, there are four “hypothetical dynamic matrices governing the processes related to the perinatal level of the unconsciousness”,[24] called “basic perinatal matrices” (BPM).[24] These BPM's correspond to the stages of birth during the process of childbirth.[25]

This is the original symbiotic unity of the fetus with the maternal organism.[25] Elements of this state can be accompanied with, or alternate with, experiences of a lack of boundaries and obstructions,[26] such as the ocean and the cosmos.[27] The extreme expression of the sacred and spiritual quality of BPM I is the experience of cosmic unity and the unio mystica.[27]

This matrix starts with the onset of labor.[28] The intrusion of chemicals and the pressures of labor change the situation in the womb, and “interrupt the fetus’ blissful connection with the mother and alter its pristine universe.”[28] Accessing this layer gives rise to strong feeling of “no escape”.[28] When experiencing this level, the sense of loneliness and helplessness is overwhelming.[29]

This matrix is connected with the move of the fetus through the birth channel.[30] It involves a struggle for survival.[31] When experiencing this layer, strong aggression and demonic forces are encountered.[32] Biographical memories associated with this matrix include struggles, fights, and adventurous activities.[33]

This matrix is related to the stage of delivery, the actual birth of the child.[34] The build up of tension, pain and anxiety is suddenly released.[34] The symbolic counterpart is the Death-Rebirth Experience, in which the individual may have a strong feeling of impending catastrophe, and may be desperately struggling to stop this process.[35] The transition from BPM III to BPM IV may involve a sense of total annihilation:[35]

  This experience of ego death seems to entail an instant merciless destruction of all previous reference points in the life of the individual.[35]

According to Grof what dies in this process is “a basically paranoid attitude toward the world which reflects the negative experience of the subject during childbirth and later.”[35] When experienced in its final and most complete form,

  ...ego death means an irreversible end to one's philosophical identification with what Alan Watts called skin-encapsulated ego."[35]

sources

• Butler, Renn (2009), Archetypal Astrology and Transpersonal Psychology: The Research of Richard Tarnas and Stanislav Grof
• Grof, Stanislav (1988), The Adventure of Self-Discovery. Dimensions of Consciousness and New Perspectives in Psychotherapy and Inner Exploration, SUNY Press