Normal bi-parietal diameter (BPD) measurement of full term fetal head is……….
A. 11.4 cms
B. 9.5 cms
C. 8.5 cms
D. 10.5 cms
Correct answer: B. 9.5 cms
Explanation
Normal bi-parietal diameter (BPD) of a full-term fetal head = ~9.5 cm
Explanation
- Bi-parietal diameter (BPD) is the transverse diameter of the fetal skull, measured between the two parietal eminences (side-to-side of the head).
- It is an important obstetric measurement used to assess fetal head size, gestational age, and cephalopelvic proportion.
Normal values
- At term (≈ 40 weeks), the average BPD is about 9.5 cm
(usually ranges 9.2–9.8 cm).
Why 9.5 cm is correct
- This diameter corresponds to a well-flexed vertex presentation, which is the most common and favorable position during normal vaginal delivery.
- Larger diameters (e.g., occipito-frontal, mento-vertical) are seen in deflexed or face presentations and are not normal BPD values.
Key point for exams
✔ Normal BPD at full term = 9.5 cm
Other Options Details
Normal bi-parietal diameter (BPD) of a full-term fetal head = ~9.5 cm
Now, explanation of all options:
A. 11.4 cm
- This diameter is too large to be the biparietal diameter.
- Around 11–11.5 cm corresponds more closely to the occipito-frontal diameter, not BPD.
- ❌ Incorrect for BPD
B. 9.5 cm ✅ Correct Answer
- Biparietal diameter (BPD) is the transverse diameter of the fetal skull.
- It is measured between the two parietal eminences.
- Normal BPD at full term = 9.5 cm
- ✔️ Correct
C. 8.5 cm
- This measurement is smaller than normal term BPD.
- Seen in preterm fetus or growth-restricted babies.
- ❌ Incorrect for full-term fetal head
D. 10.5 cm
- This value is larger than normal BPD.
- More suggestive of suboccipito-frontal diameter or abnormal head size.
- ❌ Incorrect
✅ Final Answer: B. 9.5 cm
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Writer: Vandita Singh, Lucknow (GS India Nursing Group