From the Research
The cardinal movements of labor are best described as 4 key rotational movements, including engagement, descent, flexion, internal rotation, extension, external rotation, and expulsion, but recent evidence suggests that only 4 rotational movements are necessary, excluding engagement, descent, and expulsion 1. The mechanics of labor describe the forces required for fetal descent, and the movements that the fetus must perform to overcome the resistance met by the maternal bony pelvis and soft tissue.
- The 4 rotational movements are:
- Internal rotation
- Extension
- External rotation
- Flexion These movements are essential for a successful vaginal delivery as they allow the fetus to navigate the curved and narrow birth canal by presenting the smallest possible diameter of the fetal head at each stage, facilitating passage through the maternal pelvis with minimal trauma to both mother and baby. The information gathered by clinical examination and ultrasound should be integrated into clinical decision making, as ultrasound offers a historically unique opportunity for noninvasive, dynamic studies of the mechanics of labor 1. Recent studies have focused on the importance of freedom of movement during labor, but the definition of cardinal movements has been clarified to include only the necessary rotational movements 1. Other studies have investigated the influence of laboring people's mobility and positional changes on birth outcomes, but the primary focus remains on the essential rotational movements of the fetus during labor 2.