Labour arrest and prolonged labour

Definition

Stages of labour

• The first stage divides into a latent and an active phase (from 5–6 cm).
• The second stage begins at full cervical dilatation.
• A partogram serves graphic documentation of the course of labour.

Arrest of labour

• In the active first stage arrest means at >4 h of no progress despite adequate contractions.
• In the pushing phase the limits are primipara 2 h (epidural 3 h), multipara 1 h (epidural 2 h).

• Arrest in the first stage: no progress in dilatation and station over a defined period despite adequate contractions.
• Arrest in the second stage: no descent despite active pushing over a defined period, longer with an epidural in place than without.
• Before making the diagnosis always check: contraction quality, membrane status, bladder filling, lie and position, analgesia, maternal position.

• Protracted labour is abnormally slow cervical dilatation or fetal descent, labour arrest a complete halt in progress; both can occur in any stage of labour, and uniform definitions are lacking.
• According to ACOG the active first stage begins at 6 cm (5 cm according to WHO); arrest is absent cervical change for 4 hours despite adequate contractions with ruptured membranes, and the latent phase is prolonged beyond 20 hours in nulliparous and 14 hours in multiparous women.
• The second stage is considered prolonged in nulliparous women after more than 3 hours without or more than 4 hours with epidural analgesia, and in multiparous women after more than 2 or 3 hours respectively; the third stage normally lasts no more than 30 minutes.

Aetiopathogenesis

Aetiology and risk factors

• The course of labour depends on the "4 Ps": power (contractions), passage (bony pelvis), passenger (fetus) and presentation.
• Causes are fetopelvic disproportion due to a small pelvis, a large fetus or abnormal presentation, lie or position, and contractions that are too weak or infrequent (hypotonic) or occasionally too strong or frequent (hypertonic).

Clinical features

Uterine inertia

• Primary inertia is present from the onset of labor.
• Causes are exhaustion, uterine overdistension or fear.

Clinical features and complications

• In hypotonic labour, particularly in the active phase, inadequate contractions fail to produce sufficient cervical dilatation and descent; labour becomes protracted.
• Fetal macrosomia is both a cause of protracted labour and a risk factor for shoulder dystocia and severe perineal laceration.

Diagnosis

• The diagnosis is clinical; labour progress is assessed about every 2 to 4 hours, with or without vaginal examination.
• Uterine activity is assessed for strength and frequency by palpation or an intrauterine pressure catheter; clinical or ultrasound estimation of fetal weight helps to identify macrosomia.

Keep learning in the app

Further reading (selection)

1. StatPearls: Hypotonic Labor (NCBI Bookshelf)
2. MSD Manual Professional Edition: Protracted or Arrested Labor
3. DocCheck Flexikon, Eröffnungsperiode
4. DocCheck Flexikon, Geburtsstillstand

Cross-references