Fetal Senses

Fetal sensitivity made simple

Have you ever wondered if your baby can hear sounds in the womb? What about if he or she can feel your movements the same way you can feel your baby move? Can he or she feel pain?

For most of the previous century, scientists didn't think that a fetus had the ability to sense anything inside the womb. Most scientists believed that any movement on the part of a fetus was due to involuntary reflexes and had nothing to do with reacting to sensory input. A fetus' brain, it was thought, was not developed enough to truly sense anything.

 

This line of thought began to change a few decades ago, though. We've learned more about fetal brain development and the ability of fetuses to sense external stimuli. Now, we have evidence that a fetus can not only feel when it's being touched in the womb, it can also hear, taste and even smell.

Touch

Experiments have demonstrated that fetal sensitivity to touch begins as early as week 8 of pregnancy. The areas that develop the ability to sense touch first are the areas in the adult body that have the most sensory receptors: the palms, soles and genitals. At birth, nearly every part of the body can sense a light touch.

Hearing

Although there are several barriers that shield the fetus from the outside world (including the amniotic fluid, embryonic membranes and even the mother's abdominal muscles), sounds and vibrations still permeate into the womb. In fact, studies have shown that voices can be heard by the fetus. The voice of the mother is especially strong because it can travel to the fetus through her body tissue, rather than through the air.

Startling sounds have been shown to increase a fetus' heart rate and, conversely, soothing sounds can slow it down. Many pregnant women report feeling increased fetal movement in response to loud noises, such as in a movie theater, as well. We have evidence that listening begins as early as week 16 of fetal development (which is particularly notable because the ear is not even done developing until around week 24).

Taste and Smell

Testing infants shortly after birth has shown us that they emerge from the womb with the ability to discriminate between different tastes and scents. This proves that these senses have been activated prior to birth. Indeed, experiments have shown that a fetus will react to different odors and tastes that pass through the placenta into the amniotic fluid. For example, fetuses have been shown to respond favorably when their mothers eat sweet food. The flavor enters the amniotic fluid and increased swallowing on the part of the fetuses may be observed. The opposite can happen with bitter and sour tastes.

Sight

It's hard to say whether a fetus can see inside the womb. For one, the eyelids are closed until about week 26 of development. What we do know is that babies born prematurely rarely display the ability to visually track objects until about week 32.