The three-dimensional images captured by scientists through magnetic resonance imaging (MRI) technology, showed how the head and skull are shaped when passing the birth canal before childbirth. Olivier Ami of the University of Kloofen, France, and his colleagues published these latest research results in PLOS ONE.
Doctors have known that the baby’s head shape might be changed during labor and these changes are so-called “head molding”, which occurs in the second stage of labor when the baby leaves the uterus and passes through the birth canal. However, the researchers still don’t know the detailed information on how the infant’s head is being reconstructed during the stage. Only one study ever before captured the image of the process.
In this new study, Ami and his colleagues used 3D MRI to capture detailed images of the skull and brain of seven infants before and during the second phase of labor. The analysis showed that all of the seven infants’ heads had their own head molding, to be specific, different parts of the skull were, more or less, overlapped during the second stage of labor. After labor, five of the seven infants’ head and brain shape returned to the prenatal status, but the other two are still under the process of head molding. Of the three infants with the highest degree of head molding, two were born through an emergency Caesarean section, while the other one was delivered through the vagina.
Overall, the results of the study indicate that an infant bears more pressure than we previously estimated during labor, which might be the potential reason why some newborns are diagnosed with asymptomatic cerebral hemorrhage and retinal hemorrhage after vaginal labor. The authors point out that more studies are needed to prove the surmises, but their work demonstrated the value of three-dimensional MRI in capturing fetal head molding.
Ami added: “During the vaginal labor, the shape of fetus head will be reconstructed to varying degrees depending on how the skull is overlapped. For most newborns, fetal cranial molding is invisible when labored. Some skulls are molded (compliance), making it easier to come out, while other skulls are not easy to be molded (non-compliance).”
Ami O, Maran J-C, Gabor P, Whitacre EB, Musset D, Dubray C, et al. (2019) Three-dimensional magnetic resonance imaging of fetal head molding and brain shape changes during the second stage of labor. PLoS ONE 14(5): e0215721. doi.org/10.1371/journal.pone.0215721