CHAPTER XI
UNUSUAL PRESENTATIONS AND POSITIONS
Breech Presentation.—The pelvic pole enters the inlet first, once in thirty cases and more commonly in primiparas than otherwise.
Etiology.—Anything that interferes with or deranges the laws of normal gestation will predispose to, or produce this anomaly.
Thus, if the head is too large, as in hydrocephalous, or if the fœtus is too movable, as in hydramnios, or if an obstacle, like placenta previa, contracted pelvis or tumors prevent the proper approach of the head to the inlet, the mechanism will be disturbed and a breech or possibly a shoulder presentation will result.
Abnormal flaccidity of the uterine or abdominal walls, prematurity or twins also contribute definitely to its occurrence.
The attitude of the child generally retains its normal aspect of complete flexion. This pose, however, is not maintained invariably for on occasion the buttocks and genitals may rest upon the inlet while one or both feet may be extended on the thighs and lie beside the neck, or the thighs may be extended while the knees remain flexed, and what is known as a knee presentation, or if the foot comes down, a footling presentation results.
Positions.—The sacrum is the most prominent bony landmark of the breech, hence the positions are named from the relation this bone bears to the four quadrants of the inlet.
Fig. 61.—The breech. Left-sacro-anterior position. (Lenoir and Tarnier.)
We have therefore in their order of frequency the following designations: Left-sacro-anterior, where the sacrum lies to the left of the median line of the mother’s body and in front; right-sacro-anterior, where the sacrum lies to the right and in front; right-sacro-posterior, where the bone lies near the mother’s vertebral column, and on the right side; and the left-sacro-posterior position, where the bone occupies a corresponding place on the left side.