The association of parturition scars and pelvic shape: A geometric morphometric study

Abstract

Objectives: Pelvic features, mostly known as parturition scars, have been extensively studied in the last decades and are frequently investigated in archaeological and forensic contexts. It is still unclear, however, whether they really relate to pregnancy and birth, or whether these features are caused by other biomechanical factors. Because the length and difficulty of labor correlates with the form of the birth canal, we studied the association between the expression of pelvic features and pelvic shape using geometric morphometrics. Materials and Methods: We scored the expression of the preauricular sulcus, margo auricularis groove, sacral preauricular extension, dorsal and ventral pubic pitting for 54 individuals from a 19th century collection and 19 individuals from the Bronze Age cemetery of Hainburg-Teichtal, Austria. Based on photogrammetric surface models, pelvic shape was captured by 331 landmarks and semilandmarks. The multivariate association between pelvic features and pelvic shape was explored by partial least squares analysis. Results: Within the female subsample, we detected a significant association of a constrained birth canal with a strong expression of the preauricular sulcus, the margo auricularis groove, and a retroverted position of the acetabulum. No significant association was found among males. Discussion: This suggests that difficult or prolonged labor may indeed cause more strongly expressed pelvic features, presumably because of increased strain of the pelvic ligaments during birth. Furthermore, the retroversion of the acetabulum, which is known to cause sacroiliac joint dysfunction, changes the strain on pelvic ligaments and can thus also result in the development of pronounced pelvic features.

Are parturition scars truly signs of birth? The estimation of parity in a well‐documented modern sample

“…The literature has documented different frequencies of dorsal pubic pitting in different historic and archeological populations (e.g., Cox, 1989; Maass, 2012; Rebay‐Salisbury et al, 2018; Waltenberger, Pany‐Kucera, et al, 2021). Our model can be used to estimate and compare the average parity in these groups.…”

“…However, the causes of parturition scars are still not well understood because some parous women never express them whereas some nulliparous women or even men develop them (Holt, 1978). The association with stature, as well as pelvic shape and size, suggests that biomechanical strain also influences the expression of parturition scars (Decrausaz, 2012; Waltenberger, Pany‐Kucera, et al, 2021). Because of the multiple factors involved in the development of “parturition scars,” we use the more neutral term “pelvic features” (Pany‐Kucera et al, 2019) to refer to the structures traditionally described as parturition scars.…”

“…Sulci and pits are probably provoked by lateral tensions to the pelvic ligaments, whereas the extended pubic tubercle is influenced by longitudinal stress of the rectus abdominal muscle (Hirschberg et al, 1998). In both sexes, pelvic features are also related to body weight, the size and shape of the pelvic inlet (Decrausaz, 2012; Waltenberger, Pany‐Kucera, et al, 2021) and age. The preauricular sulcus, for instance, becomes deeper during an individual's lifetime (Bergfelder & Herrmann, 1980).…”

Pelvic inlet area is associated with birth mode

“…Our landmark scheme consisted of 274 3D landmarks per pelvis, measured on each surface model (Figure 1A ). This scheme was modified according to Reynolds and Young, 13 Fischer and Mitteroecker 26 and Waltenberger et al 14 The list of landmark points and their descriptions are included in Table S1 . Of these 274 points, 83 were anatomical landmarks and 191 were curve semi‐landmarks, which were placed along bony edges of the pelvis such as the pelvic inlet, iliac crest, ischial tuberosity, and obturator foramen.…”

Indicators of motherhood? Sacral preauricular extensions and notches in identified skeletal collections

“…the extended pubic tubercle (Cox, 1989 ), we prefer the neutral term “pelvic features” (PF) to specify pelvic modifications in this context. Because of the high intra‐ and inter‐population variability, as well as the range of other factors that play a role in the aetiology of pelvic features (e.g., age, stature, pelvic dimensions, biomechanical and musculoskeletal conditions and hormonal influences), the context of origin for most of the “classic” features remains under debate; some studies found relationships to giving birth, while others did not (e.g., Bergfelder & Herrmann, 1980 ; Cox, 1989 ; Igarashi et al, 2019 ; McArthur et al, 2016 ; McFadden & Oxenham, 2017 ; Pany‐Kucera et al, 2019 , 2021 ; Perréard Lopreno & Brůžek, 2010 ; Snodgrass & Galloway, 2003 ; Stewart, 1970 ; Suchey et al 1979 ; Waltenberger et al, 2020 ). The focus of this paper is on the occurrence of extensions or notches at the ventral apex (i.e., ventrosuperior margin of the sacral ala) of the sacrum, described within the framework of the ERC‐funded project “The value of mothers to society,” aiming to assess prehistoric women's reproductive and social status.…”