"It has been proposed that arguments around fetal pain can be resolved by the fact that the fetus never enters a state of wakefulness in utero. This evidence is derived largely from observations of fetal lambs. Rigatto et al., for example, directly observed an unanaesthetised sheep fetus, in utero, through a Plexiglas window, for 5000 hours without observing signs of wakefulness such as eyes opening or coordinated movement of the head. Several factors explain this lack of wakefulness, including the environment of the womb, which is warm, buoyant and cushioned, and the presence of a chemical environment (most notably adenosine) that preserves a continuous sleep-like unconsciousness or sedation and suppresses higher cortical activation in the presence of intrusive external stimulation. Mellor et al. also propose that the fetus is unconscious based on the presence of sleep-like EEG patterns observed in the lamb fetus, which enter a more quiescent state together with lack of movement, during hypoxic stress, although it should be emphasised that this is quite different from the kind of noxious stress generated by surgery discussed here. Mellor et al. report that the general pattern of EEG during gestation is equivalent to a sleep-like state analogous to non-rapid eye movement and rapid eye movement sleep."