Question

The four cardinal movements, flexion, internal rotation, extension, and restitution with external rotation, constitute part of the normal mechanism of labor. The chronological order in which they occur is

• A. Flexion, internal rotation, extension, restitution and external rotation
• B. Internal rotation, flexion, extension, restitution and external rotation
• C. Flexion, extension, restitution and external rotation, internal rotation
• D. Internal rotation, extension, restitution and external rotation, flexion

Hint:

Walk through how the head has to turn and tilt as it moves down and out of the birth canal.

Answer 1

The Correct Option is A

This question asks for the correct order of four steps in the normal mechanism of labor, out of the full sequence that also includes engagement, descent, and expulsion.

1. Flexion: As the head meets resistance going down the birth canal, the chin tucks in. This happens first, and it lets the smallest head diameter enter the pelvis.
2. Internal rotation: Once flexed and at the level of the ischial spines, the head turns so its longest diameter lines up with the widest part of the pelvic outlet. This naturally follows flexion.
3. Extension: As the head reaches the vulva and passes under the pubic arch, it straightens out, since the birth canal curves forward at this point. This comes after rotation, once the head is ready to be born.
4. Restitution and external rotation: After the head is out, it twists back in line with the shoulders, and then turns again as the shoulders rotate to pass through the pelvis. This is the last of the four steps, happening only after the head has already delivered.

Following the head's journey down and out gives the order, flexion first, then internal rotation, then extension, and finally restitution with external rotation.

Let's summarize:

• Flexion helps the smallest head diameter enter the pelvis.
• Rotation and extension prepare the head to pass under the pubic arch and be born.
• Restitution and external rotation happen only after the head is delivered.

So the correct chronological order is flexion, internal rotation, extension, then restitution and external rotation, which is sequence 1, 2, 3, 4.