What the Unborn Child Senses

In addition to its rapid physical development in the womb, which includes, as we have seen, an impressive repertoire of movement patterns, the child's senses also start to emerge during the prenatal period. As noted previously, the olfactory nerve, which is integral to the sense of smell, is present on the 35th day after conception. The foundation of the sense of smell is established on the 39th day when nerve fibers in the brain connect with the olfactory lobe.

At eight weeks after conception, local stimuli can induce partial closing of the fingers, opening of the mouth, and squinting. And during the eleventh week, if the region around the mouth is stimulated, the child will open its mouth and suck a finger.

The child can respond to sounds from the tenth to fourteenth weeks after conception. Changes in its heart rate, eye blinks and movements have occurred after sounds.

Taste buds begin to form during the eighth week after conception. An unborn child actually has more taste buds than a newborn and probably has a sense of taste.

The reflexes between the taste buds and facial muscles are in place by the twenty sixth to twenty eighth weeks after conception. A facial response was evoked at this time when a bitter-tasting substance was given to a child.

Unborn children may have a sweet tooth. In one case, a child swallowed more amniotic fluid when it was sweetened. In another, the child responded to the addition of a bad-tasting substance to the amniotic fluid by reducing its sucking movements.

We can't, of course, ask an unborn child if it experiences pain. However, research suggests that the answer would likely be that it does.

From the fifth week after conception onward, pain pathways are running from sensory receptors in the skin to those in the brain. These nerve endings are at least as dense in the skin of a newborn as in an adult. Such receptors appear around the mouth during the fifth week after conception and are present in the face, palms, and soles of the feet by the ninth week, spreading to the trunk, arms and legs by the thirteenth weeks and to all areas of the skin by the eighteenth week.

The development of the neocortex, the largest part of the brain, begins six weeks after conception and a full complement of nerve cells is present by the eighteenth week. At this time the pieces are in place to complete the pain circuitry. The evidence thus indicates that the child has developed sufficiently to sense pain late in gestation.

In a study of women undergoing amniocentesis during the third trimester, the sudden burst of body movements that the child made during the procedure may reflect a response to pain. These movements occurred when the needle either struck the child or the child moved against the needle. In another study, the child's heart rate increased in response to scalp blood sampling, a procedure that is likely to be painful.