Masters Theses

Date of Award

6-1978

Degree Type

Thesis

Degree Name

Master of Arts

Major

Anthropology

Major Professor

William M. Bass

Committee Members

Fred H. Smith, Richard L. Jantz

Abstract

Research concerned with the osteological alterations in the pelvic girdle thought to be associated with pregnancy and parturition is fairly recent. Much of the research in this area has dealt with the osteological alterations seen on the anterior and posterior pubic facies. The research on the sacroiliac joint has leaned toward the preauricular sulcus of the ilium. Consequently, data pertaining to the osteological alterations thought to be associated with pregnancy and parturition seen on the lateral margins of the anterior face of the first through third sacral vertebrae are not complete. It is my intention in this thesis to demonstrate what changes thought to be associated with pregnancy and parturition may be seen on the anterior and posterior pubic facies, the preauricular sulcus of the ilium and the lateral margins of the anterior face of the first through third sacral vertebrae, in particular the sacrum.

The skeletal material used in this thesis consists of 61 males and 51 females (12 years and older) and 115 of undetermined sex (under 12 years of age) Arikara American Indians from the Mobridge collection housed in the Osteological Laboratory of the Department of Physical Anthropology at the University of Tennessee, Knoxville, and in the Department of Physical Anthropology at the Smithsonian Institution, Washington, D.C.

Osteological alterations of the pelvic girdle thought to be associated with pregnancy and parturition include new bone formation and bone resorption in the form of depressions, pits, cavities and grooves. The presence, position and frequency of the changes seen in the pelvic girdle thought to be associated with pregnancy and parturition were visually noted. The size (length, width and depth when applicable) of the alterations were determined through measurements. In an attempt to explain how and why these changes may be present, hypotheses were proposed.

The data suggest that osteological alterations seen on the anterior and posterior pubic facies, the preauricular sulcus of the ilium and the lateral margins of the anterior face of the first through third sacral vertebrae in female skeletal material are associated with pregnancy and parturition. The changes associated with pregnancy and parturition are seen on those areas of the bone that are subject to great stress during pregnancy and parturition: the sites of attachment for the interpubical ligaments, the sacroiliac ligaments, the uterine ligaments, the perineal muscles and the anterior abdominal muscles. The changes similar to those associated with pregnancy and parturition were not seen in any of the skeletal material under the age of 12 years and were rarely seen in the male skeletal material over the age of 12. If changes thought to be associated with pregnancy and parturition had been present in skeletal material under the age of 12 years and no explanation could be offered then our assumptions of associating alterations in the pelvic girdle with pregnancy and parturition would be wrong. The presence of changes similar to those associated with pregnancy and parturition in some of the male skeletons may be explained through the natural stresses from physical exertion commonly experienced by both males and females. The alterations are more extensive in the female skeletal material because the effects of physical exertion are exaggerated during pregnancy. Through changes in body function during pregnancy, bone composition is altered, muscular tissue is subject to excessive strain and the blood clotting factor is hampered. The results are new bone formation and bone resorption in the form of depressions, pits, cavities and grooves.

Determination of the number of births per female was not possible because a population for which the actual number of births per female is documented was not available. As a result, the data presented in this thesis can only suggest that alterations present on the anterior and posterior pubic facies, the preauricular sulcus of the ilium and the lateral margins of the anterior face of the first through third sacral vertebrae may help to indicate males, nulliparas (females having given no births), primiparas (females having given one birth) or multiparas (females having given two or more births).

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