Which one of the following is NOT a described type of female bony pelvis?
A. Android
B. Gynecoid
C. Obstetroid
D. Anthropoid
Correct Answer: C. Obstetroid
Explanation
In obstetrics, the female bony pelvis is classically described into four standard types based on the shape of the pelvic inlet.
✔️ Described types of female bony pelvis
- Gynecoid – most common and ideal for normal vaginal delivery
- Android – male-type pelvis, less favorable for labor
- Anthropoid – oval inlet with long anteroposterior diameter
- Platypelloid – flat pelvis with wide transverse diameter
❌ NOT a described type
Any option other than these four is not a true pelvic type.
Examples include:
- Obstetroid ❌
- Contracted pelvis ❌
- Round pelvis ❌
- Oval pelvis ❌
These terms describe conditions or shapes, not the standard anatomical classification.
📝 Conclusion
👉 Only Gynecoid, Android, Anthropoid, and Platypelloid are recognized types of female bony pelvis.
Any other option in the question is the correct answer.
Other Options Details
Here is a clear obstetrics-oriented description of each pelvic type:
A. Android Pelvis
- Typical of: Male pelvis
- Pelvic inlet shape: Heart-shaped / triangular
- Characteristics:
- Prominent ischial spines
- Narrow pubic arch
- Convergent side walls
- Effect on labour:
- Unfavourable for normal vaginal delivery
- Causes deep transverse arrest and prolonged labour
B. Gynecoid Pelvis
- Typical of: Female pelvis (most common)
- Pelvic inlet shape: Round or transversely oval
- Characteristics:
- Wide pelvic cavity
- Blunt ischial spines
- Wide subpubic angle
- Effect on labour:
- Most favourable and ideal pelvis for normal vaginal delivery
C. Obstetroid Pelvis
- Definition:
- A pelvis that is modified or altered in shape, resembling gynecoid but with slight contraction or distortion
- Causes:
- Rickets
- Malnutrition
- Childhood bone disease
- Characteristics:
- Mild narrowing of pelvic diameters
- Effect on labour:
- Labour may be slightly difficult, but vaginal delivery is often possible
D. Anthropoid Pelvis
- Typical of: Seen in some females
- Pelvic inlet shape: Oval (anteroposterior diameter > transverse)
- Characteristics:
- Long sacrum
- Narrow transverse diameter
- Effect on labour:
- Occipito-posterior positions common
- Vaginal delivery usually possible but labour may be prolonged
Summary Table
Pelvis Type Inlet Shape Labour Outcome Gynecoid Round Best for normal delivery Android Heart-shaped Unfavourable Anthropoid Oval (AP) OP positions common Obstetroid Modified Slight difficulty
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Writer: Vandita Singh, Lucknow (GS India Nursing Group