What is the commonest cause of Postpartum Hemorrhage?

Appeared in: HP CHO -9 October 2022

Explanation

Uterine atony, the failure of the uterus to contract sufficiently after delivery, is the most frequent cause of obstetrical hemorrhage.
After placental separation, the myometrium must contract to constrict the blood vessels at the implantation site.
If the uterus remains flaccid (atonic), these vessels continue to bleed, leading to PPH.
It accounts for approximately 70-80% of all PPH cases, making it the leading cause.

Option B: Sub-involution is the delayed return of the uterus to its normal size and is a cause of secondary (late) PPH, which occurs 24 hours to 12 weeks after delivery, not the most common cause of immediate PPH.
Option C: Birth injury (trauma), such as lacerations to the genital tract, is the second most common cause of PPH, accounting for about 20% of cases, but it is not the most common cause.
Option D: Puerperal sepsis (postpartum infection) can lead to hemorrhage, but it is typically a cause of secondary (late) PPH, not the most common cause of immediate PPH.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Causes of Postpartum Hemorrhage (PPH) as background academic context rather than a clinical decision trigger.
Immediate recognition and management of uterine atony are critical nursing responsibilities. The first step is always vigorous fundal massage to stimulate uterine contraction.
Nurses must be prepared to administer uterotonic medications like oxytocin, methylergonovine, or carboprost as ordered to manage atony.
Continuous monitoring of vital signs and estimated blood loss is essential to detect hypovolemic shock early.

How to Approach the Question

Identify the core question: The question asks for the 'commonest cause' of Postpartum Hemorrhage (PPH).
Recall the primary causes of PPH. A useful mnemonic is the '4 Ts': Tone, Trauma, Tissue, and Thrombin.
Evaluate the frequency of each cause. Remember that uterine atony (Tone) is by far the most frequent, accounting for the vast majority of cases.
Analyze the options provided: 'Atony of uterus' directly corresponds to 'Tone'. 'Birth Injury' corresponds to 'Trauma'. 'Sub-involution' and 'Puerperal sepsis' are causes of secondary (late) PPH.
Select the option that represents the most frequent cause of primary PPH, which is uterine atony.

Concept Tested & Keywords

Concept Tested: Causes of Postpartum Hemorrhage (PPH)
Stem keywords: Postpartum Hemorrhage, commonest cause
Lead-in keywords: What is
Clinical cues: Age/sex group narrows the expected diagnosis, intervention, or normal reference range.

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E6 Obstetrics Williams pp. 47-67, 49-70

Practise the full HP CHO -9 October 2022

Attempt every question from this paper in a timed mock, then review the full solution for each one.