How to Understand the Mechanism of Labor

Throughout labor, primarily second stage, the baby goes through five distinct actions called the "mechanism of labor." This article explains these five actions and how they assist the baby to make his journey into the world.

Things You'll Need

• Doctor or a midwife

Instructions

1. 

   Descend down the birth canal. The baby begins to descend into the pelvis and continues through the birth canal. Descent happens due to the force of gravity and as a result of the downward pressure of the contractions during second stage.

2. 

   Touch the chin to the chest. As the baby descends, her chin touches her chest, which is known as flexion. Flexion occurs due to the pressure and resistance of the head coming through the birth canal. When flexion occurs properly, the diameter of the head is reduced by nearly one centimeter as it approaches and passes the pelvic brim.

3. 

   Internally rotate. The baby completes internal rotation. The baby's head will enter the pelvis in a transverse or diagonal position. As it reaches the pelvic floor, the occiput (the back of the head) will turn to the front of the belly (anterior), but may occasionally rotate towards the sacrum.

4. 

   Extend the head. After the occiput passes through the pelvis, the head will extend and the chin will lift off of the chest. This is called extension. This point is also considered "crowning." Shortly after the baby crowns, the head will be born.

5. 

   Turn to the side. After the head is born, it will turn to either the left or right side. This is called restitution. After restitution is completed, the shoulders will rotate internally to a diagonal plane and then come out.

Resources

• Fetal Positions and Adaptations