Researchers in France have taken 3D images that show how an infant's head changes shape during the birthing process.
Infants' Head Shape Molding Revealed for First Time
Doctors have known that the heads of infants change shape during the birthing process as a result of the pieces of their skull not being fully stitched together until several weeks after birth, but now researchers in France have been able to capture images of these changes as they happen using magnetic resonance imaging (MRI).
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One of the evolutionary adaptations that human beings have made over the years is the birthing of infants who are not fully developed the way other mammals are. Often in nature, the infants of other species are up and walking around days, hours, or even minutes after being born. This is because they leave their mother's womb in a much more developed state than human infants. Human infants, meanwhile, take months to reach the same level of development after they are born for an important reason: humans can't pass a fully developed infant head through the birth canal of the mother.
To accommodate our overly large brains, and the skulls that encase them, human infants are born before the brain has completely developed and before the skull has been fully knitted together. As a result, an infant's head is much more soft and delicate during birth, which makes it more pliable and able to pass through its mother's narrow birth canal. While doctors knew this was happening during the birthing process, they've never been able to really see it but thanks to Olivier Ami and colleagues at Auvergne University in Clermont Ferrand, Rance, they have 3D images of what this process looks like in reality.
In a new study published in PLOS One this week, Ami's was able to use 3D MRI to collect detailed pictures of seven different infants' skulls and brains before and during the second stage of labor, when the infant's head passes through the birth canal. In all seven cases, the MRI revealed detailed images of the fetal head molding as it was happening, with 5 of the infants' heads returning to their pre-second stage shape, but the changes to the head shape for two of the infants persisted after they were born.
The study's findings suggest that the stress on an infant's skull during birth is much greater than previously understood and provides clues as to the brain and retinal bleeding often seen in infants who are born vaginally rather than via C-section.
"During vaginal delivery, the fetal brain shape undergoes deformation to varying degrees depending on the degree of overlap of the skull bones. Fetal skull molding is no more visible in most newborns after birth. Some skulls accept the deformation (compliance) and allow an easy delivery, while others do not deform easily (non-compliance)," Ami said.