The emergence of the mind—a borderline of human viability?

Abstract

The moment of birth is the moral and legal point when human life must be preserved independent of gestational age, according to the Nuffield Council on Bioethics (1). Alternative views such as the newly formed embryo or a baby with a capacity for self-awareness were proposed by some of the distinguished members of the council or working party, but the consensus was that birth is straightforward to identify and usually represents a significant threshold in potential viability. A prerequisite is that the newborn 'encompasses the capacity to breathe either independently, or with a support of a ventilator'. The working party defines a borderline of viability at or before the gestational age of 25 weeks. Babies born above the borderline without major malformations should be resuscitated and treated with intensive care if necessary. Infants born between 24 and 25 weeks of gestation should be offered full intensive care unless the parents and the clinicians agreed that it is not in the best interest of the baby. Between 23 and 24 whole weeks the parents can chose whether they wish resuscitation and intensive care of the baby. Below 23 weeks the standard practice is not to resuscitate. This extensive report of about 250 pages written by leading professionals in philosophy, law, sociology, anthropology, medicine and nursing besides representative laymen is thorough and impressive. I agree with most of the arguments and conclusions. However, the definition of borderline of viability can be discussed. The survival and possibly also the prognosis for infants born 23–24 weeks seem to be better in for example Scandinavia (2) and also at several centres in North America and Australia than in the UK. The main shortcoming of this report is that the development of the brain and the emergence of consciousness are barely discussed at all. I could not even find the word consciousness in the index, although it appears in the text. To use the onset of air breathing even in a ventilator as a breaking point can be dubious in the near future. It may be possible to sustain life of newborns below 23 weeks or exteriorized fetuses by oxygenation with fluid ventilation or extracorporeal oxygenation of the blood (ECMO). To use air breathing as a hall-mark will be as old-fashioned in the near future as to define death only as definitive heart arrest. The formation of the nervous system in the third postconceptional week has been used as a hall-mark, when experiments on human embryos in vitro are no longer allowed (3). An alternative limit of viability could be when a fetus or a preterm infant has developed a brain to achieve a minimal level of consciousness (4, 5). However, this raises a new question—how to define consciousness? A simple definition of consciousness is awareness of the body, the self and the world. Even the preterm infant fulfils some criteria of being conscious. It can be awakened, show emotions and interact socially. Recently, it has been demonstrated that noxious stimuli are processed in the somatosensory cortex already at about 30 gestational weeks (6, 7). However, first after about 24 weeks there is an ingrowth of thalamocortical axons in the somatosensory, auditory, visual and frontal cortex (see Ref. 8). Thus infants born before 24 weeks do not seem to have any anatomical ability to be conscious at a cortical level. However, we cannot exclude the possibility of some kind of consciousness at a subordinate level. Newborns below 23 weeks, anencephalic infants and some severely brain damaged infants (e.g. neonatal encephalopathy grade III) are less likely to be conscious even at a minimal level and therefore it should be possible to withhold or withdraw treatment. Thus instead of using the onset of breathing air as a crucial limit of viability, I think it is now time to discuss the emergence of a minimal consciousness as an alternative threshold. Hugo LagercrantzEditor-in-Chief