In human fetal skull distance between the centre of bregma to the nape of the neck, is termed as
A. suboccipito bregmatic
B. mento vertical
C. submento bregmatic
D. suboccipito frontal
Correct Answer: A. suboccipito bregmatic
Explanation
The distance from the centre of the bregma to the nape of the neck in the human fetal skull is called the occipito-frontal diameter.
Explanation
- Bregma:
The junction of the sagittal suture and coronal suture (anterior fontanelle). - Nape of the neck:
Corresponds to the occipital region of the fetal skull. - The straight line measured from the centre of bregma to the occiput (nape of neck) represents the occipito-frontal diameter.
Important points
- Name: Occipito-frontal diameter
- Length: Approximately 11.5 cm
- Seen in:
- Deflexed head
- Typical of vertex presentation with incomplete flexion
- Clinical importance:
A larger diameter compared to suboccipito-bregmatic, so labour may be longer or more difficult.
Summary
✅ Correct term: Occipito-frontal diameter
📏 Length: ~11.5 cm
🧠 From: Centre of bregma → Nape of neck
Other Options Details
These terms describe antero-posterior diameters of the fetal skull, important in obstetrics because the diameter that presents depends on the attitude (flexion/extension) of the fetal head during labor.
A. Suboccipito-bregmatic diameter
- From: Subocciput → Bregma
- Length: 9.5 cm
- Head attitude: Complete flexion
- Presentation: Vertex (normal)
- Clinical importance:
✔️ Smallest AP diameter
✔️ Most favorable for vaginal delivery
B. Mento-vertical diameter
- From: Chin (mentum) → Highest point of vertex
- Length: 13.5–14 cm
- Head attitude: Partial extension
- Presentation: Brow presentation
- Clinical importance:
❌ Largest AP diameter
❌ Cannot pass through pelvis → vaginal delivery impossible
C. Submento-bregmatic diameter
- From: Submentum → Bregma
- Length: 9.5 cm
- Head attitude: Complete extension
- Presentation: Face presentation (mento-anterior)
- Clinical importance:
✔️ Same size as suboccipito-bregmatic
✔️ Vaginal delivery possible if mentum is anterior
D. Suboccipito-frontal diameter
- From: Subocciput → Frontal eminence
- Length: 10–10.5 cm
- Head attitude: Incomplete flexion
- Presentation: Deflexed vertex
- Clinical importance:
⚠️ Less favorable than complete flexion
⚠️ May cause prolonged labor
Summary Table
Diameter Length Head attitude Presentation Outcome Suboccipito-bregmatic 9.5 cm Complete flexion Vertex Best Mento-vertical 13.5–14 cm Partial extension Brow Impossible Submento-bregmatic 9.5 cm Complete extension Face Possible Suboccipito-frontal 10–10.5 cm Incomplete flexion Deflexed vertex Difficult
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Writer: Vandita Singh, Lucknow (GS India Nursing Group