Stage of labour

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Stages of Labour

Labour is divided into three main stages by convention, with a commonly described fourth stage. Here is a detailed breakdown:

First Stage - Onset of Labour to Full Cervical Dilation (10 cm)

This is the longest stage. It begins with the onset of regular uterine contractions and ends when the cervix reaches full (complete) dilation of 10 cm.

Friedman's classic graphostatistical work divided the first stage into two phases, described as a sigmoid curve:

1a. Latent Phase

From onset of regular contractions to the beginning of rapid cervical change
Cervix effacess and dilates slowly
Normal duration:
- Nulliparas: mean ~6.4 hrs (up to ~20 hrs considered normal)
- Multiparas: mean ~4.8 hrs (up to ~14 hrs considered normal)
Prolonged latent phase: >20 hrs in nulliparas, >14 hrs in multiparas

1b. Active Phase

From the point where cervical dilation accelerates (classically ~3-4 cm in Friedman's era; now updated to 6 cm by ACOG/Zhang criteria)
Cervix dilates rapidly to 10 cm
Normal rate:
- Nulliparas: ≥1.2 cm/hr (Friedman); modern data allow slower rates before 6 cm
- Multiparas: ≥1.5 cm/hr
Arrest of active phase (Friedman): no dilation for ≥2 hours
The active phase is further subdivided (Friedman) into:
- Acceleration phase
- Phase of maximum slope (fastest dilation)
- Deceleration phase (just before full dilation)

Contemporary update: The Consortium on Safe Labor (Zhang et al.) challenged Friedman's thresholds using modern data (>62,000 deliveries). They found labor before 6 cm is slower than Friedman described, and true active labor (rapid dilation) does not consistently start until 6 cm. ACOG now defines the active phase beginning at 6 cm.

Characteristics of First Stage (Table from Creasy & Resnik):

Characteristic	Nulliparas (All)	Nulliparas (Ideal)	Multiparas (All)	Multiparas (Ideal)
Latent phase duration	6.4 ± 5.1 hr	6.1 ± 4.0 hr	4.8 ± 4.9 hr	4.5 ± 4.2 hr
Active phase duration	4.6 ± 3.6 hr	3.4 ± 1.5 hr	2.4 ± 2.2 hr	2.1 ± 2.0 hr

Second Stage - Full Dilation to Delivery of the Infant

Begins when cervix is fully dilated (10 cm) and ends with delivery of the baby
The fetal head descends through the birth canal; descent begins in the late first stage and accelerates into the second stage
Normal duration:
- Nulliparas: mean ~50-60 min (up to 2 hrs without epidural, 3 hrs with epidural)
- Multiparas: mean ~20 min (up to 1 hr without epidural, 2 hrs with epidural)
Key process: cardinal movements of labour (engagement, descent, flexion, internal rotation, extension, external rotation, expulsion)

Third Stage - Delivery of Infant to Delivery of the Placenta

Begins after the baby is delivered and ends with complete delivery of the placenta and membranes
Signs of placental separation: Brandt-Andrews sign, cord lengthening, gush of blood, fundal rise
Normal duration: usually within 30 minutes; >30 min is considered prolonged
Management: Active management (oxytocin + controlled cord traction) reduces postpartum haemorrhage risk

Fourth Stage - First Hour After Placental Delivery

Described by Pritchard and MacDonald
Comprises the first 1-2 hours after delivery of the placenta
Highest risk period for postpartum haemorrhage (PPH)
Uterus contracts (involution begins), vital signs stabilize
Requires close monitoring of maternal condition

Summary Table

Stage	Start	End	Key Events
1st - Latent	Regular contractions begin	~3-6 cm dilation	Cervical effacement, slow dilation
1st - Active	~6 cm dilation	Full dilation (10 cm)	Rapid cervical dilation, descent begins
2nd	Full dilation (10 cm)	Delivery of baby	Descent, rotation, expulsion of fetus
3rd	Delivery of baby	Delivery of placenta	Placental separation and expulsion
4th	Placental delivery	1-2 hrs post-delivery	Uterine involution, haemostasis

Abnormal Labour Patterns (Friedman)

Pattern	Definition
Prolonged latent phase	>20 hrs (nullipara), >14 hrs (multipara)
Protracted active phase dilation	<1.2 cm/hr (nullipara), <1.5 cm/hr (multipara)
Arrest of active phase	No dilation for ≥2 hrs in active phase
Protracted descent	<1 cm/hr (nullipara), <2 cm/hr (multipara)
Arrest of descent	No descent for ≥1 hr in second stage

Sources:

Creasy & Resnik's Maternal-Fetal Medicine: Principles and Practice - Categorization of Labor Events, p. 937
Creasy & Resnik's Maternal-Fetal Medicine - Consortium on Safe Labor data, p. 938-940

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