The most dangerous placenta previa is?

RUHS, Jaipur, M.Sc Nursing Entrance Exam-2018

Obstetrics & Gynaecology

Hard

Appeared in: RUHS, Jaipur, M.Sc Nursing Entrance Exam-2018

Explanation

Type-II posterior placenta previa is considered the most dangerous due to its location on the posterior uterine wall, overlying the sacral promontory.
This position prevents the fetal head from effectively compressing the placenta to control bleeding (a mechanism known as tamponade), as the sacrum is not a firm surface like the pubic symphysis in anterior previa.
The placenta's bulk in the posterior position reduces the anteroposterior diameter of the pelvic inlet, which can obstruct fetal head engagement.
There is a significantly higher risk of umbilical cord compression between the fetal head and the sacrum, leading to fetal asphyxia and distress.
Due to these factors, it is often referred to as 'dangerous placenta previa'.

Option A: Low-lying placenta previa means the placenta is in the lower uterine segment but does not reach the internal cervical os. While it can cause bleeding, it is generally less severe and less dangerous than types that are closer to or cover the os, especially the posterior type.
Option B: In Type-I or Type-II anterior placenta previa, the placenta is located on the front wall of the uterus. This position is less dangerous because the fetal head can descend and press the placenta against the firm pubic symphysis, which helps to control bleeding through a natural tamponade effect.
Option D: Marginal placenta previa (often classified as Type II) is when the edge of the placenta reaches the margin of the internal os but does not cover it. While it carries risks of bleeding, the specific dangers of a posterior location (ineffective tamponade, reduced pelvic space) are the key factors that make Type-II posterior the most dangerous variant.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Complications and classification of placenta previa as background academic context rather than a clinical decision trigger.
Nurses must recognize that a diagnosis of posterior placenta previa signifies a high-risk pregnancy with an elevated potential for sudden, massive hemorrhage and fetal compromise.
Key nursing interventions include strict bed rest, continuous fetal monitoring, maintaining IV access, ensuring blood products are available, and absolutely avoiding vaginal examinations, which can provoke catastrophic bleeding.
Patient education is critical, focusing on the immediate reporting of any bleeding, understanding the need for activity restriction, and preparing for a potential emergency cesarean delivery.

How to Approach the Question

First, identify the core of the question, which is to determine the 'most dangerous' type of placenta previa among the given options.
Recall the different classifications of placenta previa, including both the degree of coverage of the cervical os (low-lying, marginal, partial, complete) and the anatomical location (anterior vs. posterior).
Analyze the options provided: 'Low lying' and 'Marginal' refer to the degree of coverage, while 'Type-1 anterior' and 'Type-II posterior' specify both degree and location.
Focus on the anatomical implications of anterior versus posterior placement. Remember that the pelvis has a firm bony structure at the front (pubic symphysis) and a less firm structure at the back (sacrum).
Apply the principle of tamponade: the ability of the fetal head to compress the placenta and control bleeding. This is effective against the anterior pubic bone but ineffective against the posterior sacrum.
Conclude that the posterior location is inherently more dangerous due to ineffective bleeding control and potential for obstructing labor. Therefore, Type-II posterior is the most dangerous option.

Concept Tested & Keywords

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E6 Midwifery Obstetrics and Gynecology Nursing Sandeep Kaur pp. 18-26, 19-27