The shape of the brim in anthropoid pelvis is:
A. Triangular with base towards sacrum
B. Well-rounded
C. Square
D. Oval
Correct Answer: D. Oval
Explanation
The shape of the pelvic brim in an anthropoid pelvis is:
👉 Oval (elongated anteroposteriorly)
Explanation:
- The anteroposterior diameter is longer than the transverse diameter.
- The brim appears oval with the long axis running front to back.
- This shape resembles that seen in apes, hence the name anthropoid.
Key points of Anthropoid pelvis:
- Oval pelvic inlet (AP > transverse)
- Narrow transverse diameter
- Commonly allows occipito-posterior position during labor
- Second most common pelvis type after gynecoid
✅ Correct answer: Oval (anteroposteriorly elongated)
Other Options Details
These options describe different shapes of the pelvic inlet (pelvic brim) and are commonly related to pelvic types in obstetrics.
A. Triangular with base towards sacrum
- This inlet is heart-shaped or triangular, with the broad base posteriorly (towards the sacrum).
- It is characteristic of the Android pelvis.
- Features:
- Prominent sacral promontory
- Narrow forepelvis
- Reduced space for fetal head
- Less favorable for normal vaginal delivery.
B. Well-rounded
- The inlet is almost circular and symmetrical.
- This is typical of the Gynecoid pelvis.
- Features:
- Wide transverse and anteroposterior diameters
- No projection of sacral promontory
- Most common and ideal pelvis for childbirth.
C. Square
- The pelvic inlet appears nearly square because the anteroposterior and transverse diameters are almost equal.
- Commonly associated with the Anthropoid pelvis.
- Features:
- Long anteroposterior diameter
- Narrow transverse diameter
- Vaginal delivery is usually possible, often with occipito-posterior positions.
D. Oval
- The inlet is flattened anteroposteriorly and wide transversely, giving an oval shape.
- Characteristic of the Platypelloid pelvis.
- Features:
- Short AP diameter
- Wide transverse diameter
- Engagement of the fetal head may be difficult; labor may be prolonged.
Summary Table
Shape Pelvic Type Obstetric Significance Triangular (base to sacrum) Android Least favorable Well-rounded Gynecoid Most favorable Square Anthropoid Usually favorable Oval (flat) Platypelloid Difficult engagement
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Writer: Vandita Singh, Lucknow (GS India Nursing Group