Mrs. Y is a 24-year-old primigravida at 39 weeks gestation who presents to the labor and delivery room in active labor. On admission, the obstetrician notes that she has been pushing for 3 hours with no descent of the fetal head. What is the most likely cause of Mrs. Y's obstructed labor?

1. A

   Fetal malpresentation

2. B

   Maternal exhaustion

3. C

   Pelvic contracture

4. D

   Fetal macrosomia

Appeared in: GMCH Nursing Officer-2025

Explanation

• Obstructed labor occurs when the fetus cannot descend through the birth canal despite strong uterine contractions, due to a mechanical blockage.
• The clinical picture of a primigravida pushing for an extended period (3 hours) with zero fetal descent strongly suggests an absolute mechanical obstruction.
• This scenario points to a problem with the 'Passage' (the maternal pelvis) in the '3 Ps' of labor (Powers, Passage, Passenger).
• Pelvic contracture, a narrowing of the pelvic dimensions, is a primary cause of an inadequate 'Passage' and results in absolute cephalopelvic disproportion (CPD).
• Therefore, it is the most definitive explanation for the complete arrest of labor progress despite adequate maternal effort.

Why Other Options Were Wrong

• Option A: This is a 'Passenger' problem. While a major malpresentation like a transverse lie or brow presentation can cause obstruction, it is often identified earlier. A malposition might cause slow descent or arrest of rotation, but a complete lack of any descent for 3 hours is more characteristic of a bony obstruction.
• Option B: This is a failure of the 'Powers'. Maternal exhaustion is a consequence of prolonged and difficult labor, not the primary cause of the mechanical block. The obstruction must be present first, which then leads to exhaustion from ineffective pushing.
• Option D: This is a 'Passenger' problem that can cause 'relative' CPD. While a large baby can get stuck, it's common for there to be some initial descent and molding before arrest occurs. The complete lack of any descent from the beginning of pushing is more suggestive of an absolute bony limitation of the pelvis itself.

Related Visual

• Visual 1: Diagram - Illustration of cephalopelvic disproportion (CPD), showing a large fetal head unable to pass through a small maternal pelvis.
• Visual 2: Image - Depiction of the four main types of maternal pelves (Gynecoid, Android, Anthropoid, Platypelloid) to explain how pelvic shape and contracture can impede labor.
• Visual 3: Flowchart - Management algorithm for obstructed labor, starting from diagnosis (failure to progress on partograph) to interventions like IV fluids, monitoring, and preparation for cesarean section.

Clinical Relevance

• Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Etiology of Obstructed Labor as background academic context rather than a clinical decision trigger.
• Recognizing obstructed labor is a critical nursing skill to prevent severe maternal and fetal complications, including uterine rupture, obstetric fistula, postpartum hemorrhage, fetal distress, and neonatal death.
• The '3 Ps' (Powers, Passage, Passenger) provide a fundamental framework for nurses to systematically assess labor progress and identify the potential cause of dystocia (difficult labor).
• Prompt communication with the obstetrician about the lack of fetal descent despite strong pushing is essential for timely intervention, which is almost always a cesarean delivery in cases of true obstruction.

How to Approach the Question

• First, analyze the patient's demographic and clinical details: She is a primigravida (first pregnancy) at term (39 weeks) in active labor.
• Identify the core problem presented in the stem: She has been pushing for 3 hours with 'no descent of the fetal head'.
• Apply the '3 Ps' framework to diagnose the labor abnormality: Powers (pushing for 3 hours), Passage (pelvis), and Passenger (fetus).
• Evaluate the 'Powers': The mother is pushing, so the effort is being made. The problem is not a lack of effort, but a lack of result.
• Evaluate the outcome: 'No descent' is an absolute term. It implies a complete mechanical blockage, not just slow progress.
• Assess the options based on this analysis: Fetal malpresentation and macrosomia are 'Passenger' issues that can cause obstruction, but often allow some initial descent. Maternal exhaustion is a 'Powers' issue and a result, not a cause. Pelvic contracture is a 'Passage' issue that creates an absolute block, perfectly matching the clinical finding of 'no descent'.

Concept Tested & Keywords

• Concept Tested: Etiology of Obstructed Labor
• Stem keywords: primigravida, 39 weeks gestation, active labor, pushing for 3 hours, no descent, obstructed labor
• Lead-in keywords: most likely cause
• Clinical cues: The combination of 'primigravida', '3 hours of pushing', and 'no descent' is the classic triad pointing towards an absolute mechanical block like pelvic contracture.

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Q7Gv-Fzql69tbIOhC09J01

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