Similarly there are six face (Fig. [55]) and six breech (Fig. [56]) presentations. Thus, if the chin (mentum) is resting in the left anterior segment of the mother’s pelvis, the position would be left-mento-anterior, or L. M. A. If the breech presents and the sacrum is in that relation the position is left-sacro-anterior, or L. S. A.

Fig. 55.—Diagram showing the six possible positions in a face presentation.

In describing the transverse presentations, four words, instead of three are used; thus, left-acromio-dorso-anterior, or L. A. D. A.

There are but four varieties of transverse presentations, since the shoulder is either anterior or posterior: thus left-acromio-dorso-anterior, left-acromio-dorso-posterior and the two corresponding positions on the right side.

Fig. 56.—Diagram showing the six possible positions in a breech presentation.

During the last two to four weeks of pregnancy, particularly among the primiparæ, the top of the fundus settles to the level which it reached at about the eighth month, and the lower part of the abdomen becomes more pendulous than formerly. The patient usually breathes much more comfortably after this change in contour takes place, but, at the same time, she may have cramps in her legs as a result of the increased pressure; more difficulty in walking; frequent micturition and desire to empty her bowels, while the vaginal discharge may be considerably increased. It is at this time that the presenting part enters the superior strait and is spoken of as being “engaged.”

The time at which engagement takes place depends upon three factors: Whether the patient is a multipara or a primipara; the size and normality of the pelvis; the size and position of the fetus. It is often helpful to the obstetrician in planning for the delivery to know whether or not the presenting part is engaged, particularly in primiparæ.