PHASES and STAGES of Labor

What are the 4 phases of parturition

Phase 1: Quiescence; Phase 2: Activation; Phase 3: Stimulation; Phase 4: Involution

What is Phase 1 of parturition

Quiescence

What occurs during Phase 1 (Quiescence) of parturition

Prelude to parturition characterized by uterine quiescence and cervical softening; it begins even before implantation.

What happens to the cervix during Phase 1 (Quiescence)

The cervix undergoes softening with increased compliance while maintaining structural integrity.

What are Braxton-Hicks contractions associated with

The quiescent phase of parturition.

What is Phase 2 of parturition

Activation

What is the purpose of Phase 2 (Activation)

Preparation for labor, including uterine readiness for labor and cervical ripening.

When does Phase 2 (Activation) occur

During the last 6–8 weeks of pregnancy.

What happens to myometrial responsiveness during Phase 2 (Activation)

Myometrial unresponsiveness is suspended.

What happens to oxytocin receptors during Phase 2 (Activation)

Oxytocin receptors increase.

What happens to the lower uterine segment during Phase 2 (Activation)

The lower uterine segment forms, producing lightening or “the baby dropped.”

What cervical changes occur during Phase 2 (Activation)

Cervical ripening, effacement, and loss of structural integrity.

What happens to cervical collagen during Phase 2 (Activation)

Collagen fibrils decrease, leading to increased spacing between fibrils.

What agents promote cervical ripening during Phase 2 (Activation)

Prostaglandin E2 (PGE2), prostaglandin F2α (PGF2α), and progesterone antagonists.

What is Phase 3 of parturition

Stimulation

What occurs during Phase 3 (Stimulation)

The processes of labor: uterine contraction, cervical dilation, and fetal and placental expulsion.

What is Phase 4 of parturition

Involution

What occurs during Phase 4 (Involution)

Parturient recovery or the puerperium, including uterine involution, cervical repair, and breastfeeding.

What are the 3 stages of labor

First stage, second stage, and third stage.

What is the definition of labor

Uterine contractions that bring about demonstrable effacement and dilation of the cervix.

What does the first stage of labor begin with

The onset of regular painful uterine contractions.

What does the first stage of labor end with

Complete cervical dilation.

What cervical dilation marks the end of the first stage of labor

10 cm (complete cervical dilation).

What is the “bloody show” associated with the onset of labor

Spontaneous release of blood-tinged mucus from the cervical canal.

Why are uterine contractions painful during labor

Hypoxia of the myometrium, compression of nerve ganglia, cervical stretching during dilation, and stretching of the peritoneum overlying the fundus.

What is the Ferguson reflex

Mechanical stretching of the cervix that enhances uterine activity.

What happens to the interval between contractions during the first stage of labor

It gradually decreases from approximately 10 minutes.

What are the distinct uterine segments that develop during labor

An upper uterine segment and a lower uterine segment.

What happens to the upper uterine segment during labor

It undergoes physiological retraction.

What is the Bandl ring

A prominent pathological retraction ring that may occur when thinning of the lower uterine segment becomes extreme, as in obstructed labor.

What does the second stage of labor begin with

Complete cervical dilation (10 cm).

What does the second stage of labor end with

Delivery of the fetus.

How long do uterine contractions typically last during the second stage of labor

Approximately 30–90 seconds.

What is the average interval between contractions during the second stage of labor

Approximately 1 minute.

What is the most important force responsible for fetal expulsion in the second stage

Maternal intra-abdominal pressure.

What does fetal station describe

The descent of the fetal biparietal diameter in relation to a line drawn between the maternal ischial spines.

What does the third stage of labor begin with

Delivery of the fetus.

What does the third stage of labor end with

Delivery of the placenta and membranes.

What is the main event of the third stage of labor

Delivery of the placenta and membranes.

What is the sequence of the 4 phases of parturition

Quiescence → Activation → Stimulation → Involution

What is the sequence of the 3 stages of labor

First stage: cervical dilation → Second stage: fetal delivery → Third stage: placental delivery.