What are the FIGO diagnoses for abnormal labor patterns?

FIGO Diagnoses for Abnormal Labor Patterns

The primary abnormal labor patterns detectable during the active phase include protracted dilatation, arrest of dilatation, prolonged deceleration phase, and failure of descent, with diagnosis based on serial cervical examinations plotted graphically against time. 1

Diagnostic Framework

The diagnosis of abnormal labor patterns requires:

• Serial cervical examinations every 2 hours with graphical plotting of dilatation patterns, which remains the gold standard for detecting labor abnormalities 2
• Recognition that the active phase begins when cervical dilatation rate accelerates from the flat slope of latent phase to more rapid progression, regardless of absolute dilatation achieved 1, 2
• Understanding that uterine contraction assessment has limited diagnostic value, as contractions inconsistently increase throughout first stage and cannot reliably distinguish phases 1, 2

Specific Abnormal Labor Patterns

1. Protracted Active Phase Dilatation

Most frequently occurring dysfunctional labor pattern 3:

• Nulliparas: Dilatation rate <1.2 cm/hour 1, 2
• Multiparas: Dilatation rate <1.5 cm/hour 1, 2
• Absolute minimum threshold: <0.6 cm/hour regardless of parity 1, 4

2. Arrest of Active Phase Dilatation

• Traditional definition: No cervical change for 4 hours with adequate contractions 5
• Updated safer threshold: No cervical change for 2 hours, particularly after 6 cm dilatation 4, 2
• At 4-5 cm dilatation, the traditional 4-hour window remains appropriate 4

3. Prolonged Deceleration Phase

• Nulliparas: >2-3 hours 1, 2
• Multiparas: >1 hour 1, 2
• This pattern is strongly associated with cephalopelvic disproportion and second stage abnormalities 1
• Often accompanied by failure of descent 2

4. Failure of Descent

• Inadequate fetal descent during the active phase or second stage 1
• Frequently occurs with prolonged deceleration phase 2

Critical Pre-Intervention Assessment

Before any intervention, cephalopelvic disproportion (CPD) must be ruled out, as it occurs in 25-30% of active phase abnormalities 4, 2:

• Assess for fetal malposition (occiput posterior/transverse) 4
• Evaluate for excessive molding, deflexion, or asynclitism without descent 4
• Consider fetal macrosomia, maternal diabetes, obesity, and pelvic adequacy 4
• Perform suprapubic palpation of fetal skull base to differentiate true descent from molding 4

Underlying Risk Factors

Common etiologies requiring enhanced surveillance 1, 2:

• Cephalopelvic disproportion
• Excessive neuraxial block
• Poor uterine contractility
• Fetal malpositions and malpresentations
• Uterine infection
• Maternal obesity
• Advanced maternal age
• Previous cesarean delivery
• Fetal macrosomia

Management Algorithm

For Protracted Active Phase:

• Combined amniotomy with oxytocin augmentation when CPD is excluded 4, 2
• Oxytocin is contraindicated if CPD is suspected or cannot be excluded 4
• Amniotomy alone is insufficient and rarely produces further dilatation 4

For Arrest of Active Phase:

• Reassess for CPD if no progress after adequate contractions 4, 2
• Expect response within 2 hours (safer than 4-hour threshold) after 6 cm 4, 2
• Discontinue oxytocin if no dilatation occurs and reassess 2

For Prolonged Deceleration Phase:

• Requires even more stringent CPD exclusion 2
• Cesarean delivery is justifiable if compelling clinical evidence of disproportion exists 1
• Strongly associated with shoulder dystocia risk if vaginal delivery occurs 1

Critical Pitfalls to Avoid

• Never administer oxytocin when CPD cannot be ruled out, as obstructed labor increases uterine rupture risk 4, 2
• Never mistake molding for true descent 2
• Never diagnose protracted active phase until active phase status is verified 4
• Discharging an actively laboring patient with normal fetal heart rate is inappropriate 4
• Watch for increasingly marked molding, deflexion, or asynclitism without descent as signs of emerging CPD during augmentation 4