Obstetrics: Malpresentations and Malpositions

Malpresentations and Malpositions

• Definition: Malpresentations refer to the part of the fetus that occupies the lower pole of the uterus, other than vertex, such as breech, brow, face, or shoulder.
• Denominator: Arbitrary bony fixed point on the presenting part.
• Position: Relationship of denominator to different quadrants of the pelvis.

Risk Factors for Malpresentations

• Uterine anomalies (can be detected at first trimester scans)
• Abnormal placental location
• Congenital anomalies of the fetus
• High parity with pendulous abdomen
• Contracted pelvis
• Pelvic tumors
• Prematurity
• Polyhydraminos

Breech Presentation

• Definition: Breech presentation is when the sacrum is the denominator.
• Incidence: 20-25% at 28 weeks, 3-5% at term.
• Incidence in consecutive pregnancies: 9, 25, and 40% respectively.
• Risk factors: Prematurity, oligohydramnios, placenta previa, congenital malformation of the uterus, hydrocephalus, contracted pelvis, and cornu-fundal attachment of the placenta.

Types of Breech Presentation

• Frank breech: 60-70% (more common in primigravidas)
• Complete breech: 5-12% (more common in multigravidas)
• Footling breech: 10-30% (risk of cord prolapse 12%)

Mechanism of Labor in Breech Presentation

• Sacro-anterior position
• Engagement (bitrochanteric diameter)
• Descent with compaction (flexion)
• Internal rotation
• Flexion
• Internal rotation
• Delivery by lateral flexion

Breech Vaginal Delivery

• Spontaneous breech vaginal delivery: 10%
• Partial breech extraction/assisted breech extraction: 80-90%
• Total breech extraction: requires experienced obstetrician and anesthetist

Pinard's Manoeuvre

• For frank breech extraction
• Posterolateral aspect of the thigh
• Presses fingers into the popliteal fossa, abducts the thigh

Lovset's Manoeuvre

• For extended arms/nuchal arm
• Inclination of the pelvis allows for entry of the posterior shoulder first into the pelvis
• Principle: Rotate the body counterclockwise for right nuchal arm and clockwise for left nuchal arm

Star-Gazing Fetus

• Hyperextension >270 degrees
• 5% term breech fetus
• Vaginal delivery can result in Atlanto-occipito dislocation
• Indication for caesarean section

Dührssen Incision

• Head entrapment due to incomplete cervical dilatation
• 2, 6, and 10 o'clock position

Term Breech Trial 2000

• Randomized controlled multicentric trial
• 2088 women, 121 centers, 26 countries
• Planned caesarean section is better than planned vaginal birth
• Perinatal mortality 3 per 1000 (planned caesarean section) vs 13 per 1000 (planned vaginal birth)

Premoda 2006

• Presentation et Mode d'Accouchement (presentation and mode of delivery)
• 8,105 women, observational prospective study
• Caesarean delivery 68.8%, vaginal delivery 31.2%
• No differences in neonatal mortality rates and neonatal outcomes according to delivery mode
• Planned vaginal delivery can be offered to term breech

Adverse Outcomes of Vaginal Breech Delivery

• Overall perinatal mortality 9-25%
• Birth asphyxia
• Birth injuries
• Intracranial hemorrhage
• Long-term abnormalities

Indications for Caesarean Section

• Complicated breech (placenta previa, pre-eclampsia, contracted pelvis)
• Footling/incomplete breech
• EFW 3500 gms, BPD >9.5 cm
• Hyperextension of the neck, craniospinal angle >90
• Previous caesarean section
• Fetal anomaly that can result in shoulder dystocia

Breech Scoring System

• To be discussed

External Cephalic Version (ECV)

• Success rate: Multiparous 60%, primigravida 40%
• Increased success rates with nonobese patients, abundant amnionic fluid, and nonanterior placenta
• Indications: >36 weeks (primi), >37 weeks (multigravidas), singleton pregnancy, no GCA/FGR, liquor adequate, and membranes present
• Contraindications: antepartum hemorrhage, fetal causes, multiple pregnancy, ruptured membranes, congenital malformation of the uterus, abnormal CTG, and contracted pelvis
• Procedure: Tocolysis, epidural analgesia, forward roll, and back flip### Face Presentation
• Incidence: 1 in 500 births
• Attitude: complete flexion with spine extension (occiput in contact with the back)
• Denominator: Mentum
• Risk factors:
  • Multiparity with pendulous abdomen (70%)
  • Congenital anomalies (15%)
  • Placenta previa/cornual implantation of placenta
  • Coils of cord around neck
  • Pelvic tumor
• Palpation and vaginal examination (P/V): the mouth, hard alveolar margins, nose, malar eminences, supraorbital ridges, and mentum
• Maternal prognosis: operative delivery and vaginal manipulation
• Fetal prognosis: cord prolapse, cerebral congestion due to poor venous return, neonatal infection

Mechanism of Labour

• Mento-anterior: 60-80%
  • Engagement: submento-bregmatic
  • Descent: with extension
  • Internal rotation: late, below the ischial spines
• Mentoposterior: 20-25%
  • Engaging diameter: sub-mentobregmatic (9.5cm) or submento-vertical (11.5cm)
  • Long anterior rotation: 20-30%
  • Incomplete anterior rotation/non-rotation/short posterior rotation: 70-80%

Brow Presentation

• Incidence: 1 in 1000
• Engaging diameter: mentovertical (14cm)
• Denominator: Forehead
• Palpation and vaginal examination (P/V): supraorbital ridges and anterior fontanel
• Brow anterior: baby is small, the pelvis is roomy, good uterine contractions
• Brow posterior: not possible
• Thorns maneuver: turn brow into vertex, walking fingers over the head

Shoulder Presentation

• Incidence: 1 in 150
• Lie: transverse
• Denominator: Acromion of scapula
• Etiology:
  • Multiparity (80%)
  • Placenta previa (5-10%)
  • Prematurity
  • Uterine malformations
  • LUS fibroid
• Palpation and abdominal examination (P/A): ballotable head is felt in one iliac fossa
• Palpation and vaginal examination (P/V): acromion process, scapula, clavicle, and axilla
• Position: dorso-anterior (60%), fetus is flexed
• Complications:
  • High chances of hand and cord prolapse
  • Uterine exhaustion/rupture
  • Dehydration/ketoacidosis/shock/sepsis/peritonitis

Prognosis in Shoulder Presentation

• Overall perinatal mortality: 25-50% (vaginal delivery), 7% (caesarean delivery)
• Maternal morbidity: increased operative delivery, sequences of neglected shoulder

Management of Shoulder Presentation

• External cephalic version: all cases beyond 35 weeks
• Admitted at 37th week: elective cesarean section is the preferred method of delivery

Compound Presentation

• Incidence: 1 in 350 to 1 in 1200
• Most common cause: preterm labor
• Other causes: contracted pelvis, pelvic tumors, multiple pregnancy, macerated fetus
• Spontaneous resolution: elevation of the prolapsed limb with descent of the presenting part
• Complications:
  • Cord prolapse
  • Indication for caesarean section

Cord Presentation

• Incidence: 1 in 300
• Membranes intact: cord presentation
• Membranes rupture: cord prolapse
• Management:
  • Left lateral/exaggerated sims position/pillow under the hip
  • Foleys catheterization
  • Referral: caesarean delivery

Occiput-Posterior Presentation

• Incidence: 10% of all vertex presentations, 2% in late stages
• Causes:
  • Android or anthropoid pelvis (50%)
  • Deflexed head (high pelvic inclination)
  • Anterior placenta
  • Primary brachycephaly
• Palpation and abdominal examination (P/A): suprapubic flatness, head high, late engagement, occiput and sinciput at the same level
• Palpation and vaginal examination (P/V): posterior fontanelle is difficult to reach
• Mechanism of labor:
  • Delayed engagement (deflexed head, occiput-frontal 11.5cm, sub-occpitofrontal 10.5cm)
  • Flexion
  • Descent
  • Internal rotation (3/8th of circle)
  • Long anterior rotation; 90%
  • Short posterior rotation
  • Non-rotation
• Complications:
  • Perineal tear
  • Sagittal suture in oblique diameter, oblique posterior arrest

Labour Events in Occiput-Posterior

• First stage: prolonged, delayed engagement, premature rupture of membranes
• Management:
  • Adequate hydration
  • Premature rupture of membranes
  • Maintain partograph
  • Augmentation of labour (r/o CPD)
  • Avoid premature bearing down effort
• Second stage: prolonged, prolonged bearing down effort
• Management:
  • Frequent bladder emptying
  • Avoid poor uterine contractions
• Third stage: PPH, perineal tears (occiput-frontal diameter distends perineum)

Deep Transverse Arrest

• Definition: adequate uterine contractions, at full dilatation, head remains at level of ischial spines for >1 hour (multi), >2 hours (primi)
• Causes: android pelvis
• Options:
  • Ventouse
  • Forceps (Kielland)
  • Manual rotation (not used)
  • Caesarean section

ISOUG Guidelines

• Indications for USG in labour:
  • Objective assessment of fetal head malpresentation
  • Slow progress or arrest of labour in first stage/second stage
  • Ascertainment of fetal head position and station before considering or performing instrumental vaginal delivery
• Assessment of fetal head position:
  • AoP/angle of descent
  • Midline angle

Final Takeaway

• Breech presentation: always maintain flexion while delivering head; keep back anterior
• Face presentation:
  • Mentoanterior: head born by flexion
  • Mentoposterior: Caesarean
• Brow presentation: Caesarean
• Direct Occiput-posterior: face to pubis delivery