By: Tamsyn Helps
Ever wondered when an infant’s senses develop? Mother’s who speak to their unborn children, controversially aren’t actually crazy in assuming the fetus can hear them, according to scientific research. Scientifically it is understood that a newborn’s senses initially develop during pregnancy and are only strengthened and refined after birth.
Fetus responds to sound from 22-24 weeks by exhibiting a change in its movements.Hearing begins in low frequency and as it develops the range of frequencies it responds to increases. it is important to the remember that the fetus lies in a noisy environment and can hear the mother’s heartbeat, blood flow and digestive system.
chemosensation: fetal responses to smell and taste are difficult for the fetus to separate because the amniotic fluid bathes both receptor types.Fetus can discriminate between sweet and noxious substances added to the amniotic fluid.Fetuses increase their swallowing when a sweet substance is added to the amniotic fluid by injection. Fetuses decrease their swallowing when a noxious substance is added. The fetus begins swallowing amniotic fluid from around 12 weeks of gestation therefore the fetus will experience substances that diffuse into the fluid.
Responses to pain have been observed in premature infants from around 24-26 weeks with neural pathways for pain being formed around 26 weeks of gestation. From 23 weeks of gestation researchers have observed biochemical stress responses to needle punctures during blood transfusion.
Although it is unclear as to whether fetus are directly influenced by temperature it has been recorded that mothers feel more fetal movements when they take a hot bath. This may be due to the fact that the temperature of a mother’s womb is regulated and maintained, so there is little variation for the fetus to experience.
Touch is the first sense to develop at about 8 weeks. From about 8-9 weeks the fetus moves away from touch to its lips or cheeks. Towards the second trimester the fetus moves towards the touch. By 14 weeks, most of the body is responsive to touch except the back and the top of the head. At 13 weeks of gestation and on the fetus’ arms make contact with its face.
Vision is considered the sense least likely to be stimulated during the normal course of pregnancy. However, from 26 weeks the fetus exhibits a change in heart rate or movement when a bright light is flashed on the mother’s abdomen.
Habituation: waning of response to stimuli. The presence of a loud sound initially causes a change in heart rate and movement but as the sound is repeated the fetus’ responses wanes and eventually disappears. It is predicted that the fetus habituates to auditory stimuli at 22-24 weeks of gestation, with female fetuses habituating faster than male fetuses.
Fetuses respond differently to sounds they have not been exposed to compared to those they have. It has been documented that newborns’ prefer the sound of their mothers voice to that of unfamiliar women and prefer music they have heard prenatally, compared to music they have never heard. The ability for the fetus to distinguish between such sounds has been observed at about 36 weeks.