PRESENTATIONS OF THE Cephalic Presentation with Flexion of the Head.
Although the presentation has been regarded by almost all accoucheurs as a part of the mechanism of labor, Tarnier and Chantreuil rightly claim that it should be considered in the section on Pregnancy; for, they say, it is always of the very greatest importance to recognize the presentation during pregnancy, since it enables us to transform vicious or defective presentations into favorable ones. Let us first define what we under stand by presentation and by position.
In the earliest times, authors claimed that the foetus could present at the superior strait by any point of its surface, so that the number of pres entations and positions admitted by them was infinite. To Solayres de Renhae belongs the credit of having first attempted a classification. He was followed by Baudelocque, Gardien, Capuron, Maygrier, Duge.s; but it is to Mine. Lachapelle that wo owe the first exact definition of the words presentation and position.
To have a presentation, it is necessary that the part that tends to en gage at the superior strait be voluminous enough to almost completely fill the passage.
By position of the foetus we understand the relation of this presenting part to certain fixed points of the pelvis.
Madame Lachapelle first showed that the foetus always presents itself either by the cephalic extremity, or by the pelvic extremity, or by the trunk.
The cephalic extremity may be flexed, presentation of the vertex; or it may be extended, presentation of the face.
The pelvic extremity may be completely flexed, the inferior members being closely applied to the nates, complete presentation. It may not be completely flexed, and then becomes one of three varieties: either the thighs and legs are extended along the anterior surface of the foetus, breech presentation; or the thighs are extended upon the pelvis and the legs flexed upon the thighs, knee presentation; or both legs and thighs are extended, foot presentation.
The trunk presents always by one of its sides, left or right, but it is the shoulder that occupies the superior strait. We have therefore a presen
tation of the right shoulder, and a presentation of the left shoulder.
Adapted by Naegel(, Dubois, Stolz and all the modern accoucheurs, this classification is the one universally accepted to-day. Only, since the knee presentation is exceedingly rare, and since the mechanism of de livery is the same, whatever be the presentation, their number has been still further simplified, and we admit only three presentations, each one of which has two varieties.
1. Presentation of the cephalic extremity: head flexed, vertex: head extended, face.
2. Presentation of the pelvic extremity: complete, breech: incomplete, foot.
3. Presentation of the trunk: right lateral plane, right shoulder: left lateral plane, left shoulder.
These presentations each represent one of the main parts of the foetus, and if the parts descend vertically into the centre of the pelvis they are called clear or regular presentations. If, however, they are more or less inclined to the plane of the superior strait, they are called irregular or in clined presentations.
Inclination of the presentation will, of course, give us some varieties of the part occupying the centre of the superior strait; thus, for the vertex, we have frontal, occipital and parietal varieties; for the breech, pubic, sacral and iliac varieties; for the trunk, cervical, abdominal and costal varieties. But these irregular positions usually become regular during the course of labor. We will study them in detail when we come to de scribe the mechanism of labor. At term, as all statistics prove, vertex presentation is the rule. We will only give the figures of Dubois, of Mme. Boivin, and of Depaul. Dubois, in 2020 deliveries at term, found 1913 vertex presentations. Mme. Boivin, in 20,517 births, found 19,810 vertex presentations. It is not so in premature births. Thus in 165 dead foetuses, born before '.he sixth month, Dubois and Scanzoni found: Depaul recorded, in 16,233 accouchments, 15,119 vertex presentations.