Stages and Phases of Labor

Labor is conventionally divided into stages and phases that give clinicians and midwives a shared way to describe where a woman is in the process of giving birth. This topic sets out the standard division of labor into stages, the latent and active phases of the first stage, and how the expected tempo of each has been characterized and reassessed.

Definition

The stages of labor are the conventional divisions of parturition — first stage (onset of regular contractions to full cervical dilatation, comprising latent and active phases), second stage (full dilatation to birth of the fetus), and third stage (birth of the fetus to delivery of the placenta).

Scope

The topic covers the conventional staging of labor — the first stage (latent and active phases of cervical dilatation), the second stage (full dilatation to birth of the baby) and the third stage (birth of the baby to delivery of the placenta) — together with the graphic representation of progress over time. It is descriptive reference material on how labor is divided and described, not a protocol for diagnosing delay or intervening.

Core questions

• How is labor divided into first, second and third stages?
• What distinguishes the latent phase from the active phase of the first stage?
• How has the expected duration and tempo of each stage been described?
• Why have contemporary data revised earlier expectations of labor progress?

Key concepts

• First stage of labor
• Latent phase
• Active phase
• Second stage of labor
• Third stage of labor
• Labor curve / partograph
• Tempo of cervical dilatation

Mechanisms

The staging framework maps the physiological process onto observable milestones: cervical dilatation defines the first stage, descent and expulsion of the fetus define the second stage, and separation and delivery of the placenta define the third. Friedman's graphic analysis introduced the sigmoid labor curve, distinguishing a slow latent phase from a faster active phase of dilatation. Contemporary cohort data from Zhang and colleagues observed that the active phase may begin later and progress more slowly than Friedman's curve implied, and Cohen and Friedman have discussed how these revised descriptions should be interpreted.

Clinical relevance

The stage-and-phase framework is the common language used to record and communicate where a labor stands and to structure intrapartum observation. This entry describes that framework; it is not a rule set for diagnosing abnormal progress or deciding when to intervene in an individual labor.

Evidence & guidelines

Classic descriptions of stage duration derive from Friedman's observational work; contemporary descriptions of normal active-phase progress derive from large cohorts such as Zhang and colleagues (2010). Cohen and Friedman (2015) offer a critical discussion of how the newer curves are applied in practice, illustrating that the appropriate thresholds remain contested.

History

Friedman's 1954 graphic analysis established the stages-and-phases vocabulary and the sigmoid labor curve that dominated twentieth-century teaching. In 2010, Zhang and colleagues' analysis of contemporary births prompted a reassessment of how quickly normal labor progresses, and subsequent commentary by Cohen and Friedman (2015) debated how these findings should reshape descriptions of normal and abnormal progress.

Debates

Where does the active phase of the first stage begin?

Friedman's curve placed the active-phase acceleration earlier, whereas contemporary cohorts suggest the active phase may not clearly begin until later dilatation; the discrepancy affects how slow progress is judged.

Key figures

• Emanuel A. Friedman
• Jun Zhang
• Wayne R. Cohen

Seminal works

• friedman-1954
• zhang-2010

Frequently asked questions

What are the three stages of labor?

The first stage runs from the onset of regular contractions to full cervical dilatation, the second stage from full dilatation to the birth of the baby, and the third stage from the birth of the baby to delivery of the placenta.

What is the difference between the latent and active phases?

Both are part of the first stage; the latent phase involves slower early cervical change, while the active phase is the period of more rapid dilatation, though the exact boundary between them has been reassessed by contemporary data.