What is the correct sequence in mechanism of labour?

Appeared in: UPPSC 2022

Explanation

The question asks for the correct sequence of the mechanism of labor, also known as the cardinal movements.
The first four cardinal movements occur in a specific order to allow the fetus to navigate the maternal pelvis.
The correct sequence begins with Engagement, where the fetal head enters the pelvic inlet.
This is followed by Descent, the continuous downward movement of the fetus.
Next is Flexion, where the fetal chin tucks to the chest, presenting the smallest head diameter.
Finally, Internal Rotation occurs, where the head rotates to align with the pelvic outlet. Therefore, the sequence Engagement → Descent → Flexion → Internal rotation is correct.

Option A: This option incorrectly places Flexion before Descent and omits Internal Rotation. Extension and Crowning occur much later in the process.
Option C: This option omits the critical steps of Descent and Internal Rotation, which are necessary for the head to navigate the mid-pelvis before crowning can occur.
Option D: This option incorrectly reverses the order of Flexion and Internal Rotation. Flexion must occur before Internal Rotation to present the smallest possible diameter of the fetal head to the pelvis, which facilitates the rotation.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Mechanism of Labor (Cardinal Movements) as background academic context rather than a clinical decision trigger.
Nurses must understand the cardinal movements to assess labor progress accurately. A deviation from the normal sequence can indicate cephalopelvic disproportion (CPD) or fetal malposition, requiring intervention.
By tracking these movements through vaginal exams (assessing fetal station and position), nurses can identify labor dystocia (abnormal labor) and alert the provider.
Knowledge of the mechanism of labor helps the nurse guide the mother in pushing efforts and position changes (e.g., using gravity) to facilitate fetal descent and rotation.

How to Approach the Question

Identify that the question asks for the correct chronological order of events during labor.
Recall the cardinal movements of labor. A common mnemonic is "Every Darn Fool In Rotterdam Eats Rotten Egg Rolls Everyday" (Engagement, Descent, Flexion, Internal Rotation, Extension, Restitution, External Rotation, Expulsion).
Evaluate each option against the first few steps of this sequence.
Option A is incorrect because it omits Descent.
Option C is incorrect because it omits Descent and Internal Rotation.
Option D is incorrect because it reverses the order of Flexion and Internal Rotation.

Concept Tested & Keywords

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E6 Obstetrics Williams p. 21-39

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