Malposition and malpresentation of the fetal head

Definition

• Malposition and malpresentation of the fetal head are deviations from the normal vertex presentation, in which the flexed head leads with its smallest circumference.
• In face presentation the chin is the presenting part, in brow presentation the area between the anterior fontanelle and the orbital ridges; both result from extension instead of flexion of the neck.

Classification

Malpositions

• In deep transverse arrest of the brim (German "hoher Geradstand") suture sagittal at the pelvic inlet.
• In deep transverse arrest at the outlet the sagittal suture lies transverse at the pelvic outlet.

Malpositions

• High straight position (hoher Geradstand): the head lies in the pelvic inlet in the anteroposterior rather than the transverse diameter — try alternating positions, otherwise caesarean.

• Position describes the relationship of the presenting part to an anatomical axis; in vertex presentation occiput anterior, occiput posterior and occiput transverse positions are distinguished, occiput anterior being normal.

Occurrence & epidemiology

Epidemiology

• Face presentation occurs in about 1 in 600 births; brow presentation is considered the rarest malpresentation (about 1 in 500 to 1 in 4,000 births); the commonest malposition is occiput posterior.

Aetiopathogenesis

Aetiology and risk factors

• Maternal risk factors for face and brow presentation are preterm birth, a contracted or platypelloid pelvis, multiparity and previous caesarean section.
• Fetal risk factors are anencephaly, multiple loops of the umbilical cord around the neck, neck masses, macrosomia and polyhydramnios.

Clinical features

Clinical features and complications

• In occiput posterior position the neck is usually somewhat deflexed, so a larger head diameter passes through the pelvis; labour may arrest in the second stage.
• Brow presentation usually converts spontaneously to vertex or face presentation.

Diagnosis

• The diagnosis is usually made by vaginal examination in the second stage; in face presentation the orbital ridges, nose, malar eminences, mouth and chin are palpable, in brow presentation the anterior fontanelle and face but not the mouth and chin.
• Face presentation may be mistaken for breech; ultrasound shows a reduced angle between occiput and spine or a chin separated from the chest.

Keep learning in the app

Further reading (selection)

1. MSD Manual Professional Edition: Fetal Presentation, Position, and Lie (Including Breech Presentation)
2. DocCheck Flexikon, Hinterhauptslage
3. DocCheck Flexikon, Geburtsstillstand

Cross-references