The term 'fetus ejection reflex' was first coined by Dr. Niles Newton in her studies of pregnant mice. Newton found that when mice were stressed, labor slowed or stopped, whereas when they were placed in a familiar environment they delivered quickly. She discovered that this was due to alterations in the release of catecholamines. In early labor, stress causes a surge in catecholamines that shuts down contractions, allowing the mother animal to escape from the predator or other stressful situation. In late labor, however, a catecholamine surge causes a different reaction which Newton termed the fetus ejection reflex - a powerful, involuntary contraction together with the complete relaxation of the pelvic floor muscles, resulting in rapid delivery of the fetus with little to no harm to the mother.
Newton went on to perform some cross-cultural research. She found that in cultures where the mother was afforded privacy and the companionship of trusted helpers, quick easy labors were the norm, whereas in cultures where the mother was surrounded by bright lights and strangers in unfamiliar places, labor was viewed as a lengthy and painful process.
Dr. Michel Odent, a French physician, adopted the term for use in describing human labor in 1980. Odent's view was that “…parturition is an involuntary process and an involuntary process cannot be helped. The point is not to disturb it.” (Odent, 1987, p. 105). He stated that the reflex cannot take place if the neo-cortex is stimulated, as with bright lights, rational conversation or 'coaching' - all of these things interfere with the very basic and primitive sequence that results in the quick and relatively effortless delivery of a baby.
Odent stated that a fetus ejection reflex is easy to recognize; it usually starts with a moment of terror caused by the release of a massive adrenaline dose. This is immediately followed by irresistible contractions and a surge of energy. The mother tends to assume a more upright posture, generally bending forward. This changes the way in which the vulva opens, and protects the mother from dangerous tears. The fetus delivers quickly, and the placenta is often expelled within minutes.
I have given birth three times; twice in hospitals, and once at home. From my personal experience I can tell you that the fetus ejection reflex is a very real thing; I experienced it with my last labor.
The feeling is very difficult to describe. This is a little gross, but if you have ever had really bad diarrhea you may understand. It's a feeling of not being able to stop yourself from pushing, bearing down, no pain involved, just a total loss of control. It's a force of nature, a tidal wave of pushing, nothing exists except pushing. Forget about your "Hold your breath and count to ten"; there is nothing any voluntary effort could add to this. Every fiber of your body exists only to push. I was standing up when it hit, and as soon as my body bent, the baby dropped down from above my pubic bone, gliding effortlessly through the birth canal, and crowned. As soon as my husband had a towel ready to catch her she delivered completely. I was in a somewhat awkward position but only wound up with a tiny periurethral tear.
I firmly believe that the reason it occurred during this labor but not with the other two is that I was in my familiar environment and was allowed to be completely alone. I don't think it could have happened this way if I had been at the hospital again.
Parturient Mice: Effect of Environment on Labor. Newton, N., Foshee, & Newton, M.; Science 25 March 1966:Vol. 151. no. 3717, pp. 1560 - 1561
The Effect of Psychological Environment on Childbirth: Combined Cross -Cultural and Experimental Approach. Newton, N.; Journal of Cross-Cultural Psychology, Vol. 1, No. 1, 85-90 (1970)
The Fetus Ejection Reflex Revisited. Newton, N.; Birth Vol.14, No. 2, 106-108 (1987)
The fetus ejection reflex. Odent,M.; Birth 1987; 14: 104-105.
Fear of death during labour. Odent M.; Journal of Reproductive and Infant Psychology 1991; 9: 43-47.
The second stage as a disruption of the fetus ejection reflex. Odent M.; Midwifery Today Int Midwife. 2000 Autumn;(55):12