Obstetric Topic 28. Malpresentations

I. Overview

Definition

• Malpresentation: any fetal presentation other than cephalic vertex (occiput) at the pelvic inlet.
• Normal: longitudinal lie + vertex presentation + occipitoanterior position.
• Main malpresentations: breech, face, brow, shoulder/transverse lie, compound presentation.
• Risk factors: prematurity, multiparity, uterine anomaly/fibroid, pelvic tumor/contracted pelvis, placenta previa, polyhydramnios, multiple pregnancy, fetal anomaly.

Diagnosis

• Abdominal examination / Leopold maneuvers: lie, presenting part, fetal back, engagement.
• Vaginal examination in labor: presenting part, sutures/fontanelles, mentum, sacrum, extremity, station.
• Ultrasound: confirm presentation/lie, fetal weight, anomalies, placenta and amniotic fluid.
• Assess fetal well-being with fetal heart monitoring/CTG during labor.

II. Breech Presentation

Key Points

• Presenting part: buttocks, feet or knees; incidence about 3-4% at term.
• Types: frank breech (hips flexed, knees extended), complete breech (hips and knees flexed), incomplete/footling breech (foot/knee below buttocks).
• Causes: prematurity, uterine/fetal anomalies, placenta previa, multiple pregnancy, abnormal amniotic fluid volume, contracted pelvis.
• Diagnosis: Leopold maneuvers + ultrasound; vaginal exam may feel buttocks, sacrum, anus or feet.
• Management: offer ECV near term if no contraindication; planned cesarean is common for persistent breech; selected vaginal breech only with frank/complete breech, flexed head, favorable pelvis and expert operator.
• Complications: cord prolapse/compression, head entrapment, birth asphyxia, intracranial injury, birth trauma, maternal trauma.

III. Face and Brow Presentation

Face Presentation

• Mechanism: complete hyperextension of fetal head; presenting part = face, denominator = mentum/chin.
• Incidence: about 0.15-0.2%.
• Risk factors: high parity, prematurity, anencephaly, fetal goiter/neck mass; often idiopathic.
• Diagnosis: vaginal exam palpates mouth, nose, orbits/cheek bones; confirm by US and rule out anencephaly.
• Mentoanterior: chin under symphysis → vaginal delivery usually possible if labor progresses.
• Persistent mentoposterior or mentotransverse: cannot deliver because neck cannot extend further → cesarean section.
• Avoid vacuum extraction in face presentation.

Brow Presentation

• Mechanism: partial extension between vertex and face; presenting part = forehead/brow.
• Incidence: rare, about 0.1%.
• Risk factors: same as face presentation, plus CPD and polyhydramnios.
• Diagnosis: vaginal exam palpates anterior fontanelle and orbital ridges; mouth is not felt; confirm by US.
• Often unstable → may convert spontaneously to vertex or face.
• Persistent brow: largest head diameter presents → cesarean section unless fetus is very small or pelvis very large.

IV. Shoulder / Transverse Lie and Compound Presentation

Shoulder Presentation / Transverse Lie

• Mechanism: fetal long axis is perpendicular/oblique to maternal long axis; shoulder or arm presents.
• Incidence: <0.5%.
• Causes: prematurity, placenta previa, multiparity, uterine anomaly, pelvic tumor/contracted pelvis, polyhydramnios.
• Diagnosis: abdomen is broad; no presenting part engaged; US confirms lie/presentation.
• Antenatal management: ECV if membranes intact, no contraindication and fetal status reassuring.
• In labor / persistent transverse lie: cesarean section.
• Complications: cord prolapse, obstructed labor, uterine rupture, fetal distress.

Compound Presentation

• Definition: fetal extremity presents alongside the main presenting part, usually head + hand.
• Risk factors: prematurity, polyhydramnios, multiparity, pelvic mass, small fetus.
• Diagnosis: vaginal examination + ultrasound.
• Management: expectant if hand is beside the head and labor progresses; avoid pulling the limb.
• Cesarean section if complete extremity prolapse, cord prolapse, persistent obstruction, fetal distress or conversion to shoulder presentation.