In 2010 a woman in Germany became the first person to give birth inside a magnetic resonance imaging (MRI) scanner. The results, published May 2 in European Radiology, provide an extraordinary view of what exactly happens as a baby moves through the birth canal.

The study details how the researchers adapted a regular MRI machine to hold the mother-to-be and her accoutrements. They widened the machine's mouth to make room for the obstetrician, stripped the metallic components out of a fetal heart monitor so that it could be used near the scanner's big magnet, and laid down sheeting to protect the machine from "fluid leakages."

During labor, the 24-year-old volunteer lay supine and wore earmuffs to block out the noise of the machine. As the baby's head emerged, the machine was shut off to prevent damage to its ears.*

Movement distorts MRI images, but you can't reasonably ask a woman in labor to hold still (go ahead and try it…); the sharpest images (above) were taken before and immediately after the birth. The first (a) shows the baby heading toward the birth canal, and the following images show the uterus before (b) and after (c) it expelled the afterbirth.

Researchers were able to watch the writhing contortions of the uterine muscles and the rotation of the fetus during its journey. The images revealed "how extensively the rectum and adjacent muscles are pushed against the coccyx to enable the child to pass through the birth canal," the researchers wrote.

Although they aren't recommending that doctors should adopt this technique to monitor normal births, the research paves the way for using MRI technology to understand what goes wrong during obstructed labor—including why the baby fails to move properly through the birth canal in 15 percent of vaginal deliveries.

—Sarah Fecht

* Correction (6/11/12): This sentence originally stated incorrectly that the machine was shut off before the amniotic sack broke.