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Look Who is Sensing!

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All along pregnancy months, unborn children grow physically, mentally and physiologically. You may liken the womb to a dark cave of quiet water, and wonder how the five senses as we know them develop from the embryo stage until the baby is born.

While still in the womb, the unborn baby with all its organs in place breathes, moves, swallows amniotic fluid, and reacts to stimuli preparing itself for life. The development and conditioning processes that happen throughout the nine months are crucial to get the baby’s five senses ready for exploring the outside world.

Once the baby is born, parents are curious about its perception of what goes around it; what their newborn feels, smells, tastes, sees, and hears. In fact, some senses are fully developed at birth, while others continue to develop and acquire full capacity after birth.

Look Who is Touching

Touch is the first sense to develop in the embryo. Sensitivity starts in the cheeks then quickly extends to the palms by the 11th week and the soles by the 12th week; the abdomen and buttocks acquire sensitivity around the 17th week. The baby may experiment with this newfound sense of touch by stroking its face or sucking on a thumb, as well as feeling other body parts.

In the last trimester, gentle patting and stroking alerts the baby to the mother’s touch and it may respond by calming down or kicking and nudging. By the 32nd week, nearly every part of the baby’s body is sensitive to heat, cold, pressure, and pain.

Hence, touch is one of the newborn's most advanced senses, and it has shown to be a foundation of cognitive and emotional development. Newborns are best able to feel with their mouths, which is no surprise considering this is how infants tend to explore everything. Incredibly, one-month-old babies are able to form abstract mental images of things they have sucked on.

Severe deprivation of early touch leaves both animals and humans stunted in every way—emotionally, physically, cognitively, even immunologically. Preterm babies have thus shown to benefit from therapies like “kangaroo care”(1) and infant massage.

Look Who is Tasting

A fetus will have developed taste buds, resembling that of an adult, by weeks 13 to 15. During the last trimester, the fetus swallows up to a liter a day of amniotic fluid, which serves to get the baby accustomed to breast milk.

Amazingly, the amniotic fluid that surrounds the fetus is rich in tastes—sugars, acids, salts, as well as strong flavors from the mother’s diet such as curry, garlic, coffee, etc. Studies have shown fetus preference for sweet tastes over bitter and sour ones, evidenced by the amount of swallowing that takes place when exposed to these tastes.

Newborns can discriminate between tastes and have shown definite taste preferences. Females and heavier babies show a stronger preference for sweet tastes than boys and smaller babies. On the other hand, sour and bitter tastes provoke strong reactions in newborns, but they seem remarkably indifferent to salts.

The taste of breast milk is affected by the mother’s diet; yet, only few infants decrease their feeding in response to this. Hence, a varied maternal diet may in fact help infants be less picky eaters, since we tend to be initially averse to new flavors.

 

Look Who is Smelling

A fetal nose develops between the 11th and 15th weeks. Yet, the nasal cavity remains filled by a plug of tissue; the ability to smell thus begins around 28 weeks of gestation.

Previously, scientists thought that fetuses did not have any sense of smell, since it was assumed that smelling depended on breathing air. However, it is now believed that the amniotic fluid surrounding the fetus passes through the baby’s oral and nasal cavities, triggering both the sense of taste and smell.

Studies have shown that newborns are drawn to the odor of breast milk, although they have no previous experience with it. Researchers think this may come from cues they have learned in prenatal life, since the fetus smells almost everything the mother eats or inhales.

A newborn can reliably distinguish its mother’s breast pad from any other woman’s, as well as her neck and underarm odor. This olfactory recognition also depends on the amount of close contact, especially nose-to-skin while breastfeeding. The newborn’s familiarity with its mother’s scent also has a calming effect. Bad news for men: babies are not so quick to recognize their father’s scent.

Image Source.

Look Who is Hearing

The womb is not a silent place; there is blood whooshing through the mother’s vessels, gurgling and rumbling from her stomach and intestines, and then there are the tones of her voice and the voices of others. Sound is the major source of stimulation to a fetus; after the 6th month, it becomes its major channel of information. By the end of the second trimester, unborn babies can hear.

A fetal ear begins to form at around 8 weeks, becoming structurally complete at about 24 weeks. As early as week 18, the bones of the inner ear and the nerve endings from the brain become ready for the fetus to hear sounds such as its mother’s heartbeat; it may even be startled by loud noises!

The fetal hearing progresses as the network of nerves to the ears matures. Even though the sounds it hears are muffled, it may recognize its mother’s voice. So this might be a good time for mothers to read and even sing to their babies.

The fetal movements or body patterns may change in response to sounds. Many pregnant women report fetal jerks or sudden kicks just after a door slams or a car backfires. Also, the fetal heartbeat rate often slows down when its mother speaks, suggesting that the fetal can recognize her voice and get eased by it.

Since the baby’s hearing improves up through pregnancy, it functions fairly well at birth. In fact, a newborn has already had about 12 weeks listening experience, and even has some definite preferences about what it hears, at the top of which is its mother’s voice. Babies also prefer other complex, intonated sounds as music, lullabies, and nursery rhymes. Again, newborns do not seem to show a preference to the father’s voice before few weeks.

Image source.

Look Who is Seeing

Vision is the last sense to develop in the embryo. In uterus, the eyelids remain closed until about the 26th week in order for the retinas to fully develop. By that time, the eyes open and even begin to blink.

Just as the womb is not completely quiet, it is not totally dark, either. As early as week 18—when the eyes are still closed—the retinas can detect a small amount of light if the mother is out in the bright Sun or under strong lights.

By week 33, the pupils of the eyes can detect light, constrict and dilate, allowing the baby to see dim shapes. Experimental studies shining a bright light on the belly of a woman at the 37th week have shown the baby's heart rate speeding up, or the baby turning in response to the light. As soon as their eyes open in the womb, twins seem to have no trouble locating each other, or touching faces, or holding hands.

The sense of vision is still primitive at the time of birth, compared to the other senses. Newborns arrive with what they need; at birth, a baby's vision is perfectly focused from 20 cm to 30 cm. Newborns can recognize their mothers’ faces, even at one day of age; in general, babies prefer faces and face-like shapes to other objects.

In the first two months, babies seem to scan around until they find the edge of something, and examine that edge. Between two and three months of age, the focus shifts on finding where things are to examining what things are—scanning all over an object, and noticing much more details.

Newborns can see some color, but not really the full spectrum as color perception develops by 3-4 months. They are drawn to movement and bold contrasts, and compelled to look at novel objects.

Unborn babies inhabit mothers’ wombs for nine long months, getting ready to experience life; to feel the cool breeze and the warm Sun, to taste delicious foods and drinks, to enjoy the sounds of birds and the flowery smell of gardens. Having come out, their senses continue to develop, helping them cognize the new world they are to inhabit for the rest of their lives.

Glossary

  1. Kangaroo Care is a method of care of preterm infants, which involves infants being carried, usually by the mother, with skin-to-skin contact.

References

whattoexpect.com.au
www.teensadvisor.com
health.howstuffworks.com
www.welcomebabyhome.com

photo: https://blog.bongmi.com/data/knowledge/1084_1515119216.html

“What's Going on in There? How the Brain and Mind Develop in the First Five Years of Life”, by Lise Eliot, 1999, Bantam Books.
“The Developing Child”, 8thEd., by Helen Bee.1997, Longman Books.
“Encounters with Children”, 3rd Ed., by Suzanne Dixon and Martin Stein. 2000, Mosby Books.

*The original article was published in SCIplanet printed magazine, Summer 2013 issue.

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