Examples of the some of the various deformations of the fetus known to cause dystocia
Dystocia (dys - “bad”, tokos - “childbirth”, meaning a difficult labor) could be caused by either the mother’s body, or the shape of the fetus. In these cases, the fetal form was the sole cause of dystocia (and C-section), and in the case of the thoracopagus twins, the cause of the death of the mother.
An American Text-Book of Obstetrics, for Practitioners and Students. 1895.