Baab KL, McNulty KP, Rohlf FJ The shape of human evolution: a geometric morphometrics perspective. Evol Anthropol. 2012; 21:(4)151-65

Beischer NA, Mackay EVLondon: Saunders; 1979

Bennett VR, Myles MF, Brown LKLondon: Churchill Livingstone; 1989

Burden B, Simons M Anatomy of male and female reproduction, 14th edn. In: MacDonald S, Magill-Cuerden J Edinburgh: Elsevier, Bailliere Tindall; 2011

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

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

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

Franklin D, Cardini A, Flavel A, Kuliukas AV The application of traditional and geometric morphometric analyses for forensic quantification of sexual dimorphism: preliminary investigations in a Western Australian population. Int J Legal Med. 2012a; 126:(4)549-58

Franklin D, Flavel A, Kuliukas AV Estimation of sex from sternal measurements in a Western Australian population. Forensic Sci Int. 2012b; 217:(1–3)230.e1-5

Franklin D, Cardini A, Flavel A, Marks MK Morphometric analysis of pelvic sexual dimorphism in a contemporary Western Australian population. Int J Legal Med. 2014; 128:861-72

Fraser DM, Cooper MA, 15th edn. London: Churchill Livingstone Elsevier; 2009

Geller PL, Stockett MKPhiladelphia: University of Pennsylvania Press; 2007

Gopalan S, 10th edn. Telangana: Orient Blackswan; 2005

Hashemi AH, Erfanian M, Naghibi S Radiographic Pelvimetry of the Female Pelvis in the Iranian Population. Iranian Journal of Radiology. 2010; 7:(S1)

Hanzal E, Kainz C, Hoffmann G, Deutinger J An analysis of the prediction of cephalo-pelvic disproportion. Arch Gynecol Obstet. 1993; 253:(4)161-6

Kolesova O, Vetra J Female pelvic types and age differences in their distribution. Papers on Anthropology. 2012; 21:147-54

MacDonald S, Magill-Cuerden J, 14th edn. Edinburgh: Elsevier, Bailliere Tindall; 2011

Spörri S, Thoeny HC, Raio L MR Imaging Pelvimetry: A Useful Adjunct in the Treatment of Women at Risk for Dystocia?. AJR Am J Roentgenol. 2002; 179:(1)137-44

Tague R, Lovejoy CO The obstetric pelvis of AL 288-1 (Lucy). J Hum Evol. 1986; 15:237-55

Zuckerman S, Ashton EH, Flinn RM, Oxnard CE, Spence TF Some locomotor features of the pelvic girdle in primates. Symposia of the Zoological Society of London. 1973; 33:71-165

Female pelvic shape: Distinct types or nebulous cloud?

02 July 2015
13 min read
Volume 23 · Issue 7


The objective of this study was to re-evaluate the Caldwell-Moloy (1933) classification of female pelvic shape, which has been traditionally, and still is currently, taught to students of midwifery and medicine. Using modern pelvimetric methodologies and geometric morphometric (GM) analysis techniques, we aim to elucidate whether these classic female pelvic types are an accurate reflection of the real morphometric variation present in the female human pelvis.

GM analysis was carried out on sets of pelvic landmarks from scans of women living in a contemporary Western Australian population. Sixty-four anonymous female multi-detector computer tomography (MDCT) scans were used for most of the study and 51 male scans were also examined for comparison.

Principle component analysis (PCA) found that there was no obvious clustering into the four distinct types of pelvis (gynaecoid, anthropoid, android and platypelloid) in the Caldwell-Moloy classification, but rather an amorphous, cloudy continuum of shape variation.

Until more data is collected to confirm or deny the statistical significance of this shape variation, it is recommended that teachers and authors of midwifery, obstetrics and gynaecological texts be more cautious about continuing to promote the Caldwell-Moloy classification, as our results show no support for the long taught ‘four types’ of pelvis.

For well over 50 years, students of midwifery, obstetrics, gynaecology and related professions have been taught the Caldwell-Moloy classification of the female pelvis. While recognising variation and mixed types, the current e-book of Mayes’ Midwifery (MacDonald and Magill-Cuerden, 2011), is typical in its frank reporting and use of that system. ‘Although there are four recognised pelvic categories (Caldwell et al, 1940: Table 24.1), variations within these categories can occur. Some women may have mixed features, such as a gynaecoid posterior pelvis and android fore-pelvis’ (Burden and Simons, 2011: 286). The 10th edition of Clinical Obstetrics also gives Caldwell-Maloy classification system similar prominence (Gopalan and Jain, 2005).

The basic ‘four types of pelvis’ categorisation persists to this day and is evidenced by the fact that it is taught in many universities and colleges globally and regularly cited in university-level midwifery course compulsory texts, such as Mayes Midwifery (MacDonald and Magill-Cuerden, 2011) and Myles’ Textbook for Midwives (Fraser and Cooper, 2009) and referred to in recent studies on female pelvic shape variation (e.g. Hashemi et al, 2010). The four types of pelvis categorisation persists even though the initial simple classification was subsequently extended by Caldwell et al (1940) to include 14 sub-types, and that it has also been criticised, for example, for being overtly racist (Geller and Stockett, 2007).

Register now to continue reading

Thank you for visiting British Journal of Midwifery and reading some of our peer-reviewed resources for midwives. To read more, please register today. You’ll enjoy the following great benefits:

What's included

  • Limited access to our clinical or professional articles

  • New content and clinical newsletter updates each month