When I was in midwifery school we learned the 4 basic types of pelvises that are discussed in western medicine.  At the time, my belief system was that the information was just information to pass a test and wouldn’t change my course of care.  My initial midwifery belief systems included that if I were patient enough, the baby would come regardless of such a shape.   These four pelvic types seemed disconnected from concrete tools for progress.  I was left wondering what I would do differently to assist a birth by understanding the “four pelvic types?”

As midwives we feel and see differences in pelvises, so we know they exist.  We may feel the differences in pubic arches when there are challenges in pushing.  We can observe differences in inlets with how easy or difficult a baby’s journey might be to even engage in the pelvis.  We also know that one suspected pelvic type can seem to change from one birth to the next after bodywork, mobility in labor, or movement in pregnancy.  We also see what seems like a challenging pelvis birth large babies quite quickly and pelvises that seem like there is ample room have challenges.  Even noting these “Spectrums of Ease”, thinking and visualizing how positioning can influence the bones and soft tissues to create space can be of use as a birth worker.  It is important, however, to note the complexity of the pelvis, its mobility, and influencers.

The static 4 types of pelvises are still being taught in schools and textbooks.  In teaching Spinning Babies I choose to teach (or present) and unteach them at the same time.  It is an opportunity to see how medical information presented as unbiased can be used to expose myths including the roots of racism.  It can also be used as showing the roots of an “old story” of the static pelvis as the passageway in which the pregnant person is sorted before birth into expectations of pathology.    

It was midwife Claudia Booker who was the first person who I heard speak about such origins of the pelvic types.  What I expected to be a talk on the anthropoid pelvis became a lesson on calling out its racist history.  Caldwell and Moloy had published their initial works in 1933 in Nazi Germany when the idea of pure types of pelvises was quite convenient for Germany’s ideology.  Racism was embedded in this paper calling the anthropoid pelvis, which was mostly attributed to non-white people, that of the “primitive races.”  (Caldwell and Moloy, 1938: 5). 

In 1938, Caldwell and Moloy extended their classification to include the fact that mixed types of pelvises were more likely.  These differences were noted in the different levels of the pelvises as well as from anterior to posterior parts of the pelvis.  What this means is that what is called a gynecoid inlet might have an android outlet.  And that maybe the anterior part of the pelvis seems platypelloid but the posterior gynecoid.  Some complexity at this point was acknowledged with 14 sub-types if pelvises, and yet by the 1950s, it was the initial paper without these subtypes that was taken up by medical textbooks and then later by midwifery textbooks.  

And so what do we do about this information now?  How do we discuss the bones of the pelvis in a way that it can be both an opportunity for us to reveal myths of the roots of racism while using the various shapes and complexities of the pelvis to explore solutions around lack of progress?  I have chosen not to get rid of showing the Coldwell and Moloy model in classes, for it is another opportunity to weave in anti-racism.  It can be used as a way to rethink what is assumed as fact in our classes.  We can still recognize how various shapes of the inlet, mid-pelvis, and outlet, including the soft tissues, affects the baby’s ability to navigate a pelvis,  but we can also realize that the idea of purity in these 4 types of pelvises was used to move forward a white supremacist agenda.

Booker, Claudia MEd, CPM. Lecture. Spinning Babies World Confluence. 2016.

Caldwell WE, Moloy HC (1933) Anatomical variations in the female pelvis and their effect in labour with a suggested classification. Am J Obstet Gynecol (26): 479–505 

Caldwell WE, Moloy HC (1938) Anatomical variations in the female pelvis: their classification and obstetrical significance. Proc R Soc Med 32: 1–30 

Caldwell WE, Moloy HC, D’Esopo DA (1940) The more recent conceptions of the pelvic architecture. Am J Obstet Gynecol 40(4): 558–65 

Kuliukas, Algis, Lesley Kuliukas,  Daniel Franklin, and Ambika Flavel.  Female pelvic shape:  Dinstinct types of nebulous cloud?  British Journal of Midwifery, July 2015.  Volume 23, Number 7. 490-496.