When you hold your baby and look down at that beautiful little head, it's hard to believe that was once inside your body. Our bodies change so much and accommodate a lot of transformations during pregnancy and birth. It's downright amazing, and so is the way a baby's head changes during delivery.

As NBC News reports, seven women in France gave birth inside an MRI machine and the resulting images show "exactly how parts of the infants' skulls overlap so the heads can be delivered vaginally. During this process, the brain is also compressed."

how baby's head changes during birth

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Woah. Even the doctors in charge of the study were surprised at just how much the head changed shape to allow baby to come into the world.

"When we showed the fetal head changing shape, we discovered that we had underestimated a lot of the brain compression during birth," said Dr. Olivier Ami, who lead the research.

This change during birth is called "fetal head molding," and it happens when the baby leaves the uterus and gets down into the birth canal.

"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," says Ami.

For five of the seven babies born in the MRI machine, their little heads quickly went back to how they were before leaving the uterus. For some babies it takes longer, and for a very small number of babies, the skull is "not compliant" with compression, something Ami hopes to be able to one day predict before a mom goes into labor, because right now doctors don't have a way of knowing which babies are at risk for brain trauma (this is super rare, mamas. Dr. Ami says we're talking about "one in a thousand or less").

Most babies skulls will compress no problem, but Dr. Ami is aiming to help those few babies whose skulls won't.

"We hope in the very near future, we will be able to counsel the women correctly, inform them, and choose the best delivery mode," Ami told NBC News.

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