Alive and kicking: When fetuses feel like kicking up their heels, it may be a sign of brain development

January 9, 2019

Nothing attracts a crowd like a baby kicking in utero. When a pregnant woman’s ever-expanding bump suddenly starts perambulating, it’s hard to avoid an all-hands-on experience with anyone nearby. But why is that infant thrashing around in there?

A recent study  conducted by the Department of Neuroscience, Physiology, and Pharmacology at the UK’s University College London—and published in  Scientific Reports—has found that kicking can help the fetus to “map” his or her body and explore the surrounding womb.

Author Kimberley Whitehead, along with co-authors Judith Meek and Lorenzo Fabrizi, examined the sleep patterns of 19 newborns between the ages of 31 weeks and 42 weeks. Some of the infants studied had been born prematurely—the accurate age of a baby from conception, regardless of when he or she actually is born. For instance, an infant who was one week old but born at 35 weeks would be 36 weeks old. Infants are considered full term anywhere from 37 to 42 weeks.

According to a report by Healthline, the three researchers looked at the brainwaves that fetuses produce when they kick during rapid eye movement (REM) sleep. When the fetus moves its right hand, for example, it produces brainwaves immediately afterwards in the part of the left-brain hemisphere that processes touch for the right hand.

The brainwaves are extremely fast in premature babies. (In the case of premature babies, they would still be in the womb when these fast brainwaves occur.) By the time the babies are a few weeks old, the fast brainwaves naturally disappear.

Fetal kicks in the third trimester help the infant develop brain areas linked to sensory input. They also help the baby to form a sense of his or her own body, the scientists say.

“Spontaneous movement and consequent feedback from the environment during the early developmental period are known to be necessary for proper brain mapping in animals, such as rats. Here we showed that this may be true in humans too,” Lorenzo Fabrizi said in a statement.

“For example, it is already routine for infants to be ‘nested’ in their cots. This allows them to ‘feel’ a surface when their limbs kick, as if they were still inside the womb,” she said. The study supports the notion that sleep should be protected and interruptions minimized, as the findings show how important movement is during fetal and premature newborn sleep.

For her part, Whitehead believes that the findings could help hospitals to provide an optimal environment for infants born prematurely. “We were surprised that although the movement-evoked fast brainwaves disappear a few weeks after the average time of birth, movement continues to trigger slow brainwaves,” she said.

This draws on her team’s previous earlier research, which showed that different types of brainwaves can perform different functions in unborn children. That research showed that a big change happens at full-term age because different types of sleep start to be associated with particular brainwave patterns.

Whitehead said they plan to continue studying movement in babies, but they are also focused on how aspects of brain development are processed, such as touch and painful stimuli (as with a blood test, for example).

The medical community already knows a good deal about the quality, frequency, and perceptibility of fetal movements, Dr. Amber Samuel, medical director, Maternal-Fetal Medicine at the Obstetrix Medical Group of Houston, told Heathline. Sporadic movements at about nine or ten weeks become more organized in the second trimester. Mothers can feel a fetus kick as early as 15 weeks.

As the brain develops, the fetus kicks and responds to his or her own brain activity, as well as to changes in maternal movement, sound, temperature, and other stimuli.

“The perception of fetal movement changes in the third trimester to body rolling more often than distinctive kicks but all fetal movement is reassuring even if the quality evolves,” Samuel said.

Fetal kicking serves several purposes, added Sullivan. The first is that it gives muscles and limbs exercise. It also shows response to stimuli and, as the current study suggests, helps the brain make connections for spatial sense.

And for the pregnant mother the kicking is also a learning experience. She gets chance to see how big and active her baby has become—and maybe even to hold a hand or a foot.

Research contact: @uclnpp

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