Salient. Victoria University Student Newspaper. Volume 39, Number 18, July 26, 1976.
Response to Painful Stimuli
Response to Painful Stimuli
The fetus also responds violently to painful stimuli - needle puncture and injection of cold or hypertonic solutions - stimuli which you and I find painful, children will tell you are painful, and the neonate, to judge from his responses, finds painful.
However, I have been told by advocates of abortion that we have no proof that the fetus actually feels pain. Strictly, they are quite correct. Pain is a peculiarly personal and subjective experience and there is no biochemical or physiological test we can do to tell that anyone is in pain - phenomenon which makes it very easy to bear other people's pain stoically, which is an important point for obstetricians to remember.
By the same token we lack any proof that animals feel pain. However, to judge from their responses, it seems charitable to assume they do. Were this not so there would be no point in having an organisation like the Society for Prevention of Cruelty to Animals, and I for one would be unhappy to think we would withhold from the human fetus a charitable consideration we were prpared to extend to animals.
The fetus responds to sound and light in utero. The fetus is startled by flash photography of a pregnant abdomen, and with a fibreoptic conduit and photomultiplier we can detect the shadow cast by the fetus on the posterior uterine wall.
In utero the light is shifted far to the red end of the spectrum and the fetus is using only his rod or low-light intensity vision, but if there is any light present at all there must be activation of visual pathways, because single-rod cells respond to single photons. The fetus lacks any images and sufficient light to practice cone vision, so that at birth he can see but does not know what he is looking at. Confident recognition of images takes five to eight months of extrauterine life to acquire.
With sound it is different, because intrauterine sounds have a pattern and a spectral composition not very different from extrauterine sounds, and the fetal inner ear or hearing mechanism is of the same magnitude and therefore responds in the same frequency range as children's or adults' ears.
It is easy to demonstrate fetal responses to external sound, and audiometric curves may be constructed by noting changes in fetal heart rate to pure tones presented by hydrophone or air microphone.
The fetus lines up under an image intensifier in a [ unclear: responds to the] contribution to an orchestral performance and to the dentist's turbine drill. Both habituation and conditioning have been demonstrated.
However it is not simple external sound which bombards the fetus. The pregnant uterus itself is a very noisy place. The loudest sounds to which the fetus is exposed are maternal borborygmi peaking to 85 or 90 decibels, about the intensity of sound of traffic in a busy city street.
Reaching and below 55 decibels the content is richer in pattern and meaning, the intermittent voice and the all pervading vascular bruits pulsing in sychrony with maternal hear beat in the great arteries supplying the uterus.
We do not think it entirely chance that babies are lulled by holding them to your chest, or the old wives' alarm clock, or the modern magnetic tape of a heart-beat, that the tick of grandfather clock in a library is a reassurance rather than a distraction, that people asked to set a metronome to a rate which "satisfies" them will pick a rate in the 50 to 90 beat per minute range, and that the majority of drum rhythms in the world reflect the measured beat of a human heart. We think this rhythm is deeply imprinted on human consciousness from fetal life.
The fetus drinks amniotic fluid in a phasic pattern from at least as early as eight weeks' gestation. By the third trimester there is a fasinating variation, some babies coyly drinking 10 ml per hour, and others boozing away at 90 ml per hour, and this variation correlates well with independently assessed feeding performance in the nursery.
The fetus drinks more amniotic fluid if it is sweetened, less if it is given an unpleasant taste. He may get hiccups, easily recognised, and as these occur in an episodic or phasic pattern, commonly at the same time each day, we suspect that they are related to fetal drinking sessions, and that he is already experiencing some circadian rhythms, of his own or exposed to mother's.
All babies are experienced in swallowing at birth, and some also in suckling. In the neurological examination of the neonate the "seeking" or "rooting" reflex is elicited by stroking the circumoral area of the baby. He turns his head to the side of the stimulus and opens his mouth, obviously a reflex by which he homes in on the nipple, which is its size, consistency and colour is simply a homing device on a positive pressure feed system, the breast.
In so far as it is very common to see fetuses lying with hands and feet in close proximity to their faces, it is not surprising that they elicit a seeking reflex themselves. Therefore, it is not dymanic, plastic, resilient, in command of [ unclear: his environment] and destiny with a tenacious purpose.