Textbook typologies: Challenging the myth of the perfect obstetric pelvis

Abstract

Medical education's treatment of obstetric‐related anatomy exemplifies historical sex bias in medical curricula. Foundational obstetric and midwifery textbooks teach that clinical pelvimetry and the Caldwell–Moloy classification system are used to assess the pelvic capacity of a pregnant patient. We describe the history of these techniques—ostensibly developed to manage arrested labors—and offer the following criticisms. The sample on which these techniques were developed betrays the bias of the authors and does not represent the sample needed to address their interest in obstetric outcomes. Caldwell and Moloy wrote as though the size and shape of the bony pelvis are the primary causes of “difficult birth”; today we know differently, yet books still present their work as relevant. The human obstetric pelvis varies in complex ways that are healthy and normal such that neither individual clinical pelvimetric dimensions nor the artificial typologies developed from these measurements can be clearly correlated with obstetric outcomes. We critique the continued inclusion of clinical pelvimetry and the Caldwell–Moloy classification system in biomedical curricula for the racism that was inherent in the development of these techniques and that has clinical consequences today. We call for textbooks, curricula, and clinical practices to abandon these outdated, racist techniques. In their place, we call for a truly evidence‐based practice of obstetrics and midwifery, one based on an understanding of the complexity and variability of the physiology of pregnancy and birth. Instead of using false typologies that lack evidence, this change would empower both pregnant people and practitioners.

Evolution of a discipline—The changing face of anatomy

“…Following next is a critique of clinical pelvimetry and the Caldwell–Moloy classification of pelvic capacity in pregnant patients by VanSickle et al ( 2022 ), and their use in predicting the expected difficulty of labor. In this article, the authors trace the racist history of these techniques and call for them to be replaced with evidence‐based practices rooted obstetrics and midwifery and not in the racist typologies that still dominate the educational landscape.…”

Race-based Versus Race-conscious Medicine in Obstetrics and Gynecology

“…Notions of racial and ethnic differences in pelvic anatomy and suitability for vaginal birth have historically racist antecedents 36. The most influential description of pelvic anatomic difference stems from the Caldwell-Moloy classification, which was proposed in 1933 and remains to this day in obstetric textbooks 37. This typology reduced a large breadth of anatomic variation into 4 subtypes of pelvic shape that were infused with racialized notions of adequacy and normalcy.…”

“…By contrast, the “anthropoid” pelvis was noted to be narrower, more common in non-White individuals, and less suited for childbirth. The anthropoid pelvis was first described as a “degraded or animalized arrangement seen in the lower races.” The parallel between the words “anthropoid” and “animal” was not incidental; it reflected intentions to debase Black individuals as anatomically deficient for the vital human act of giving birth 37…”

“…36 The most influential description of pelvic anatomic difference stems from the Caldwell-Moloy classification, which was proposed in 1933 and remains to this day in obstetric textbooks. 37 This typology reduced a large breadth of anatomic variation into 4 subtypes of pelvic shape that were infused with racialized notions of adequacy and normalcy. For example, the "gynecoid" pelvis was found mostly in White individuals and has been described as ideally suited for childbirth.…”

“…The parallel between the words "anthropoid" and "animal" was not incidental; it reflected intentions to debase Black individuals as anatomically deficient for the vital human act of giving birth. 37 Impetus for Removal of Racebased Medicine in Obstetrics and Gynecology-Vaginal Birth After Cesarean Delivery Race-based Calculator Trial of labor after cesarean delivery (TOL-AC) refers to a planned attempt to deliver vaginally by a person who has had a previous cesarean delivery, regardless of the outcome. This method provides those who desire a vaginal delivery the possibility of achieving the goal of a vaginal birth after cesarean delivery (VBAC).…”