81 Engagement is called the first movement, and descent is the gradual passage of the fetus through the birth canal and is called the second movement. In the modern Anglo-American tradition, it is common to cite 7 cardinal movements. The mentum (chin) is the presenting part. These rotational movements of the fetal head and shoulders are often called the cardinal movements. The brow or forehead is the presenting part. The top of the head is the presenting part. This is an uncommon fetal position and a vaginal birth is unlikely.Ĭommonly, this skull diameter is too large to pass through the pelvis. Many fetuses assume this attitude early in labor but convert to complete flexion as labor progresses. This position is commonly called the fetal position.
The back is usually arched, which increases the degree of hyperextension. In complete extension, the head and neck of the fetus are hyperextended and the occiput touches the fetus’s upper back.
In partial extension, the head of the fetus is extended, with the head pushed slightly backward so that the brow becomes the first part of the fetus to pass through the pelvis during birth. Moderate flexion (aka military position or sinciput), the head of the fetus is slightly flexed but held straighter than in complete flexion. In complete flexion, the head of the fetus is tucked down onto the chest, with the chin touching the sternum.
