F is for Fontanelle

We are celebrating our group prenatal class with the ABCs of prenatal classes. From A to Z let’s cover some common prenatal terms, F is for Fontanelle, and what you can learn about them from our class.

Naked baby sleeping with text: The ABCs of prenatal classes F is for Fontanelle
Photo by Lux Photography

Baby’s heads are truly incredible, from their delicious smell to their unfused bones! Whaaattt? The skulls of babies are made of boney plates that don’t fully join until after birth. The bones are kept together by fibrous joints called sutures and this flexibility allows for rapid brain growth and, importantly, navigation through the pelvis. During birth, the skull plates can overlap to help the baby’s head become as small as possible. That’s wild! We can see evidence of this in babies who come out with coneheads (or the nicer term, molding!).

So what are fontanelles? They are gaps between the skull bones and you can feel two of the major fontanelles on the top of a baby’s head, namely:
-A diamond-shaped soft spot at the front called the anterior fontanelle
-A triangle-shaped soft spot at the back called the posterior fontanelle

Fontanelles (also fontanels)

Don’t worry, these spots still have protection for the tissues beneath and the fontanelles will harden with time to become more like yours. (Are you pushing on your own skull yet?)

In labor, fontanelles can act as landmarks for practitioners to determine the position of your baby, that is which way your baby is facing. (Not to be confused with presentation which is the part of the baby coming into the canal first, generally head or bum!) Once your baby is low enough in the pelvis, your care provider can sometimes feel the sutures and fontanelles during a vaginal exam to get a sense of your baby’s position. Is this always needed? No, but in some cases this extra information is helpful.

What we cover about fontanelles in our prenatal class

Baby positioning: What is it? Does it matter? Can it affect labor?

Are there other ways to determine your baby’s position?

What vaginal exams can and cannot tell us

Interesting facts about fontanelles

Did I mention that because of fontanelles and sutures the skull plates can overlap? Look at this wild photo from an MRI of a baby before and during the pushing stage of labor from this paper.

Look at the shifting of the plates shown in red and green. Same baby from before labor (left) and during the pushing stage (right) (Ami et al. 2019)

Doctors always check on how the plates are closing up but they also gain information from checking the fontanelles. A sunken fontanelle may be an indication of dehydration and a bulging one may be a sign of an infection.

Up next G is for…
Back to E is for Engorgement

Learn more about our prenatal classes.

Baby photo by Lux photography – Maternity/newborn/family photographer in Montreal



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