In a 34‑week pregnant woman with a brow presentation on ultrasound, what is the expected course of labor?

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Last updated: September 8, 2026 • View editorial policy

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Cesarean Section is Usually Required for Brow Presentation

Cesarean section is the expected and necessary mode of delivery for persistent brow presentation, as vaginal delivery is rarely achievable and carries unacceptable maternal and fetal risks. 1

Understanding Brow Presentation

Brow presentation represents a malpresentation where the fetal head is partially extended, presenting the largest diameter of the fetal skull to the maternal pelvis. This creates mechanical impossibility for safe vaginal delivery in the vast majority of cases.

Expected Course and Management

Why Cesarean Section is Required

The 2023 American Journal of Obstetrics and Gynecology guidelines explicitly identify brow presentation as a signal of concern and a strong indicator for cephalopelvic disproportion (CPD), alongside other malpresentations 1. The guidelines emphasize that:

  • Brow presentation is associated with marked deflexion of the fetal head, which prevents normal descent through the pelvis
  • When CPD cannot be ruled out with reasonable certainty in the presence of malpresentation, cesarean delivery is the more prudent and safer choice
  • The risks of damage to mother and fetus are too great to attempt vaginal delivery, which is unlikely to be achievable safely 1

Clinical Decision-Making Algorithm

  1. Confirm brow presentation through clinical examination during labor (if it persists from the 34-week ultrasound finding)

  2. Assess for associated risk factors that compound the problem:

    • Fetal macrosomia
    • Maternal pelvic dimensions
    • Degree of molding and asynclitism
    • Evidence of CPD

  3. Monitor for spontaneous conversion: While some brow presentations may spontaneously convert to face (mentum anterior) or vertex presentations during labor, this is uncommon and unpredictable

  4. Proceed to cesarean section if brow presentation persists, as vaginal delivery attempts carry excessive risk

Important Caveats

Spontaneous Repositioning (Option C)

While spontaneous conversion from brow to vertex or face presentation can theoretically occur, this is not the "expected" course and should not be relied upon for management planning. The guideline evidence emphasizes preparing for cesarean delivery rather than waiting for unlikely spontaneous correction 1.

Vaginal Delivery (Option B)

Vaginal delivery is NOT usually successful with brow presentation. The guidelines explicitly state that attempting vaginal delivery with malpresentation when CPD cannot be excluded poses unacceptable risks 1.

Forceps Delivery (Option D)

Forceps delivery is contraindicated in brow presentation. The guidelines warn against "undertaking a difficult vaginal operative delivery" when malpresentation and potential CPD are present 1. The mechanical disadvantage of brow presentation makes instrumental delivery both technically impossible and dangerous.

Clinical Pitfall to Avoid

Do not adopt a "wait and see" approach hoping for spontaneous conversion. The guidelines emphasize that it is better to err on the side of intervention by cesarean delivery in the presence of uncertainty about potential harm rather than allowing labor with false hope for safe vaginal delivery 1.

Answer: A. Cesarean section is usually required

References

1
Guideline

the active phase of labor.

American Journal of Obstetrics and Gynecology, 2023

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This information is intended for healthcare professionals. Any medical decision-making should rely on clinical judgment and independently verified information. The content provided herein does not replace professional discretion and should be considered supplementary to established clinical guidelines. Healthcare providers should verify all information against primary literature and current practice standards before application in patient care. Dr.Oracle assumes no liability for clinical decisions based on this content.