Most common cause of primary post-paum hemorrhage is:
**Question:** Most common cause of primary post-partum hemorrhage is:
A. Placental abruption
B. Uterine atony
C. Vaginal bleeding after delivery
D. Aplasia/hypoplasia of uterus
**Core Concept:**
Post-partum hemorrhage (PPH) refers to excessive bleeding that occurs after childbirth, particularly after vaginal delivery. The two main types of primary post-partum hemorrhage are placental-related and uterine-related causes.
**Why the Correct Answer is Right:**
B. Uterine atony is the most common cause of primary post-partum hemorrhage, specifically referring to uterine relaxation or spasm dysfunction. This can lead to inadequate uterine contractions and inability to maintain uterine involution, causing excessive blood loss after childbirth.
**Why Each Wrong Option is Incorrect:**
A. Placental abruption: This refers to detachment of the placenta from the uterus before or after delivery, which is a separate entity and not directly related to the primary cause of PPH.
C. Vaginal bleeding after delivery: This is a symptom rather than a cause of PPH. Vaginal bleeding is a manifestation of the underlying cause and not the primary cause itself.
D. Aplasia/hypoplasia of uterus: This refers to a congenital or acquired absence/reduced size of the uterus, which is a rare cause of PPH. In this case, the uterus is unable to contract effectively, leading to excessive blood loss.
**Clinical Pearl:**
Primary post-partum hemorrhage is a critical emergency in obstetrics that requires prompt assessment and management. Identifying the underlying cause is crucial for appropriate treatment, such as uterotonic administration, manual compression, or surgical intervention (e.g., hysterectomy) when necessary.
**Correct Answer:** B. Uterine atony
**Core Concept:** Uterine atony is the most common cause of primary post-partum hemorrhage, particularly in the first 24 hours after delivery. It results from inadequate uterine contractions and failure of the uterus to contract effectively postpartum.
**Why the Correct Answer is Right:**
Uterine atony is often related to inadequate uterotonic response following delivery. Uterotonic agents, such as oxytocin and prostaglandins, are essential for uterine contraction and involution after childbirth. When uterine atony occurs, contractions fail, leading to excessive blood loss.
**Why Each Wrong Option is Incorrect:**
Option A (placental abruption) is a separate entity related to placental separation before or after delivery; this is not the primary cause of PPH.
Option C (vaginal bleeding after delivery) is a symptom rather than a cause; it is the outcome of the primary cause, not the actual cause itself.
Option D (hypoplasia/aplasia of uterus) refers to congenital or acquired absence/reduced size of the uterus, which is a rare cause of PPH and is distinct from uter