The commonest presentation of fetus at the onset of labour is
A. Podalic presentation B. Vertex presentation C. Shoulder presentation D. Face presentation
Correct Answer: B. Vertex presentation
Explanation
The commonest presentation of the fetus at the onset of labour is the Vertex presentation.
Explanation:
- Vertex presentation means the head is presenting, with the occiput (back of the head) leading.
- It occurs in about 95–96% of term pregnancies.
- This presentation allows the smallest diameter of the fetal head (suboccipito-bregmatic) to pass through the birth canal, making normal vaginal delivery most favorable.
Why other presentations are less common:
- Breech presentation: ~3–4%
- Face presentation: ~0.2%
- Shoulder (transverse lie): ~0.3%
✅ Correct answer:
Vertex presentation
Other Options Details
These are types of fetal presentation, which describe the part of the fetus that occupies the lower pole of the uterus and enters the pelvic inlet.
Explanation of each option 👇
A. Podalic presentation
- Definition: A type of breech presentation in which one or both feet present first.
- Types:
- Single footling
- Double footling
- Engaging diameter: Variable (small and irregular)
- Clinical significance:
- High risk of cord prolapse
- Poor cervical dilatation
- Usually requires cesarean section
- Common in: Prematurity, placenta previa, polyhydramnios
B. Vertex presentation
- Definition: The head is flexed, and the vertex (top of skull) presents.
- Engaging diameter: Suboccipito-bregmatic (9.5 cm)
- Position: Occiput is the denominator
- Clinical significance:
- Most common and most favourable presentation
- Allows smooth vaginal delivery
- Incidence: About 95% of term pregnancies
C. Shoulder presentation
- Definition: A transverse lie where the shoulder presents.
- Denominator: Acromion
- Engaging diameter: None (cannot engage)
- Clinical significance:
- Vaginal delivery is impossible
- High risk of uterine rupture
- Managed by cesarean section
- Seen in: Multiparity, placenta previa, uterine anomalies
D. Face presentation
- Definition: The fetal head is fully extended, and the face presents.
- Denominator: Mentum (chin)
- Engaging diameter: Submento-bregmatic (9.5 cm)
- Types:
- Mentum anterior → vaginal delivery possible
- Mentum posterior → vaginal delivery not possible
- Causes: Cephalopelvic disproportion, fetal anomalies, lax abdominal wall
Summary Table
Presentation Fetal Part Presenting Vaginal Delivery Podalic Feet Usually No Vertex Vertex of head Yes (best) Shoulder Shoulder No Face Face Sometimes (if mentum anterior)
✅ Most favourable for vaginal delivery: Vertex presentation
❌ Least favourable: Shoulder and podalic presentations
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Writer: Vandita Singh, Lucknow (GS India Nursing Group