Malpresentations (breech, face, brow)

Malpresentations - An Overview

• Definition: Any fetal presentation other than vertex (occiput anterior), where the fetal head is well-flexed. Occurs in ~5% of term labors.
• Etiology: Results from abnormal fetal lie (longitudinal, transverse, oblique) or attitude (flexion/extension of head).
• Core Types:
  • Breech: Buttocks or feet first (~3-4% of term pregnancies).
  • Face: Fully extended head, face presents.
  • Brow: Partially extended head.
  • Shoulder: Transverse lie.
• Diagnosis: Leopold maneuvers, vaginal exam, confirmed via ultrasound.

⭐ Most breech presentations (frank, complete, footling) diagnosed before term will spontaneously convert to vertex by the onset of labor.

Breech Presentation - Bottoms-Up Baby

• Definition: Fetal buttocks or feet present at the pelvic inlet.
• Types:
  • Frank: Hips flexed, knees extended (most common, ~65%).
  • Complete: Hips & knees flexed.
  • Incomplete/Footling: One or both feet extended below the buttocks.
• Risk Factors: Prematurity, multiple gestation, polyhydramnios, uterine anomalies (e.g., fibroids, septum), fetal anomalies (e.g., anencephaly).

• Management Algorithm:

⭐ Cord Prolapse: Highest risk with footling breech presentation due to poor cervical effacement and a non-engaged presenting part.

Face & Brow - Head Held High

• Pathophysiology: Fetal head is extended, preventing flexion.
  • Face: Full extension. Denominator: Mentum (chin).
  • Brow: Halfway extension. Largest diameter presents.
• Diagnosis: Vaginal exam reveals facial features (mouth, nose) or brow (frontal bones, orbital ridges).

• Management Flow:

⭐ Exam Tip: For face presentation, delivery route depends entirely on the chin's position. If Mentum Posterior (chin towards maternal sacrum), vaginal delivery is impossible due to hyperextension of the fetal neck. It is an absolute indication for C-section.

High-Yield Points - ⚡ Biggest Takeaways

• Breech presentation is the most common malpresentation; consider external cephalic version (ECV) at >37 weeks.
• Frank breech (hips flexed, knees extended) is the most frequent type.
• Face presentation with a mentum anterior position may allow for vaginal delivery.
• Mentum posterior face and persistent brow presentations are absolute indications for C-section.
• Brow presentation is unstable and has the largest anteroposterior diameter, obstructing labor.
• Ultrasound is definitive for diagnosis.