LIE Relationship of the long axis of the fetus to the long axis of the mother.
PRESENTATION The part of the fetus that lies over the inlet. The three main presentations are cephalic (head first), breech (pelvis first), and shoulder.
PRESENTING PART The most dependent part of the fetus, lying nearest the cervix. During vaginal examination, it is the area with which the finger makes contact first.
ATTITUDE Relationship of fetal parts to each other. The basic attitudes are flexion and extension. The fetal head is in flexion when the chin approaches the chest and in extension when the occiput nears the back. The typical fetal attitude in the uterus is flexion, with the head bent in front of the chest, the arms and legs folded in front of the body, and the back curved forward slightly.
DENOMINATOR An arbitrarily chosen point on the presenting part of the fetus used in describing position. Each presentation has its own denominator (i.e., occiput, sacrum, mentum, frontum).
POSITION Relationship of the denominator to the front, back, or sides of the maternal pelvis.
The two lies are: (1) longitudinal, when the long axes of the fetus and mother are parallel, and (2) transverse, or oblique, when the long axis of the fetus is perpendicular or oblique to the long axis of the mother.
All terms of direction refer to the mother in the standing position. Upper means toward the maternal head, and lower toward the feet. Anterior, posterior, right, and left refer to the mother’s front, back, right, and left, respectively.
Longitudinal lies are grouped into: (1) cephalic, when the head comes first, and (2) breech, when the buttocks or lower limbs lead the way (Table 7-1).
TABLE 7-1:FETOPELVIC RELATIONSHIPS ACCORDING TO FETAL POSITION ||Download (.pdf) TABLE 7-1: FETOPELVIC RELATIONSHIPS ACCORDING TO FETAL POSITION
|Presentation ||Attitude ||Presenting Part ||Denominator |
|Longitudinal lie (99.5%) || || || |
| Cephalic (96%-97%) ||Flexion ||Vertex (posterior part) ||Occiput (O) |
| ||Military ||Vertex (median part) ||Occiput (O) |
| ||Partial extension ||Brow ||Forehead (frontum) (Fr) |
| ||Complete extension ||Face ||Chin (mentum) (M) |
|Breech (3%-4%) || || || |
| Complete ||Flexed hips and knees ||Buttocks ||Sacrum (S) |
| Frank ||Flexed hips, extended knees ||Buttocks ||Sacrum (S) |
| Footling: single, double ||Extended hips and knees ||Feet ||Sacrum (S) |
| Kneeling: single, double ||Extended hips; flexed knees ||Knees ||Sacrum (S) |
|Transverse or oblique lie (0.5%) || || || |
| Shoulder ||Variable ||Shoulder, arm, trunk ||Scapula (Sc) |
Cephalic presentations are classified into four main groups, according to the attitude of the fetal head:
Flexion is present when the baby’s chin is near his or her chest (Fig. 7-1A). The posterior part of the vertex is the presenting part, and the occiput ...