Stages of Labor: Dilation, Expulsion, Placental — Complete Guide

1. General definitions

• Physiological labor — labor with a single fetus at 37+0 – 41+6 weeks, in cephalic presentation, via natural birth canal.
• Onset of labor — regular uterine contractions (1–2 per 10 min) with progressive structural changes of the cervix.
• Braxton Hicks "false" contractions — irregular, without cervical dilation.
• Classically 3 stages; some schools distinguish a "prelude" (latent phase) and "Stage IV" (2 hours postpartum — observation in the delivery room).

2. Stage I — Dilation

• From the onset of regular contractions to full cervical dilation (10 cm).
• Two phases: latent (up to 6 cm) and active (6–10 cm).
• Latent: slow, up to 20 hours in nulliparous women without risk factors (ACOG norm).
• Active: in nulliparous women ≥ 1 cm/h, in multiparous women ≥ 1.5 cm/h.
• Mechanisms: coordinated myometrial contraction + progressive shortening and effacement of the cervix + dilation.
• Completed by — full dilation and rupture of amniotic membranes (if not ruptured earlier).

3. Management of Stage I

• Monitoring of contractions: frequency, intensity, duration (every 30 min in latent phase, every 15 min in active phase).
• Fetal heart rate — CTG or auscultation every 15–30 min.
• Assessment of dilation — vaginal examination every 4 hours (more frequently only when indicated).
• Maternal monitoring: BP, pulse, temperature every 4 hours.
• Pain relief: epidural analgesia, nitrous oxide, opioids (as indicated).
• Partogram (WHO): graphical representation of labor progress; "action line" — if delayed, cause assessment and intervention are required.

4. Stage II — Expulsion

• From full dilation to the birth of the fetus.
• Two substages: passive (head in the pelvis, no urge to push) and active (pushing + contraction).
• Duration (active):
• — Nulliparous without epidural: ≤ 3 hours.
• — Nulliparous with epidural: ≤ 4 hours.
• — Multiparous without: ≤ 2 hours.
• — Multiparous with: ≤ 3 hours.
• Uterine contraction + maternal voluntary effort (pushing 3 times per contraction, exhaling with closed glottis).
• Position: semi-sitting, lateral, squatting, in water — in the absence of contraindications.

5. Biomechanism of labor (occiput anterior position)

• 1. Engagement of the fetal head — sagittal suture in the transverse or oblique diameter of the pelvic inlet.
• 2. Flexion of the head — chin presses against the chest, leading point is the posterior fontanelle.
• 3. Internal rotation of the head — occiput rotates anteriorly toward the pubic symphysis (sagittal suture in the anteroposterior diameter of the outlet).
• 4. Extension — birth of the head: successively occiput, vertex, forehead, face, chin.
• 5. External rotation of the head + internal rotation of the shoulders — sagittal suture returns to the transverse diameter.
• 6. Birth of the shoulder girdle: anterior shoulder from under the symphysis, then posterior over the perineum.
• 7. Birth of the torso.

6. Assessment of descent (station)

7. Stage III — Placental stage

• From the birth of the baby to the delivery of the placenta (placenta + membranes).
• Duration 5–30 min; > 30 min is delayed, increased risk of hemorrhage.
• Active management (WHO 2012): oxytocin 10 IU IM immediately after fetal birth; controlled cord traction; uterine massage.
• Expectant management — without oxytocin (only upon maternal request and at low risk); higher risk of hemorrhage.
• Mechanism of separation: 1) central by Schultze (more common, hematoma in the center of the placenta, external bleeding after delivery); 2) marginal by Duncan.
• Signs of separation: Schroeder sign (uterus rises above the umbilicus and deviates to the right), Kustner-Chukalov sign (umbilical cord does not retract when pressing above the symphysis), Ahlfeld sign (ligature on the cord descends).

8. Postpartum hemorrhage (PPH)

• Primary — within the first 24 h; > 500 ml (vaginal) or > 1000 ml (Cesarean section).
• Causes — "4T": Tone (atony — 70 %), Trauma ( lacerations), Tissue (retained placenta), Thrombin (coagulopathy).
• Algorithm: uterine massage + oxytocin 20–40 IU IV infusion; methylergometrine (contraindicated in hypertension); carboprost; misoprostol rectally.
• Balloon tamponade (Bakri), compression sutures (B-Lynch), embolization, hysterectomy — if conservative measures fail.
• Restoration of BCC, blood products, tranexamic acid 1 g IV.

9. Fetal assessment in labor

• Baseline rate: 110–160 bpm.
• Variability: 6–25 bpm (moderate) — normal.
• Accelerations — transient ↑ ≥ 15 bpm × 15 sec — reassuring sign.
• Decelerations: early (response to contraction, benign), variable (cord compression), late ( uteroplacental insufficiency — ominous sign).
• CTG categories (NICHD):
• — I: normal, no interventions.
• — II: indeterminate — monitoring + fetal scalp stimulation, maternal O₂, repositioning.
• — III: abnormal — urgent delivery (operative vaginal delivery or Cesarean section).
• Fetal scalp blood pH (if available) — for further clarification.

10. Complications and indications for intervention

• Shoulder dystocia — "obstetric emergency": McRoberts maneuver, suprapubic pressure, Rubin, Woods, Gaskin (all-fours) maneuvers.
• Fetal distress — Cesarean section or operative vaginal delivery (vacuum extraction, forceps).
• Oxytocin labor augmentation — in case of protracted labor, adequate contractions with insufficient activity.
• Amniotomy — accelerates dilation, but ↑ risk of infection and cord prolapse.
• Episiotomy — strictly by indications (not routine); mediolateral is preferred over midline.
• Manual exploration of the uterine cavity — for retained placental parts, massive hemorrhage.

11. Partogram

• Graphical record of labor progress: cervical dilation (Y-axis) vs time (X-axis).
• Alert line — expected progression; action line — 4 h to the right.
• If the curve crosses the action line — evaluation of causes is indicated (inadequate contractions, dystocia, malpresentation).
• Also records: CTG, BP, maternal pulse, temperature, fetal station, medications.
• Modern WHO 2020 modification — "LCG" (Labour Care Guide) — a more flexible format.

12. FAQ

What is the difference between true labor contractions and Braxton Hicks contractions?
True contractions are regular, increasing in intensity, with shortening intervals, do not subside with rest and a warm bath; accompanied by structural changes in the cervix. Braxton Hicks are irregular, mild, and diminish with movement.

When is active management of the third stage indicated?
For all women routinely (WHO, RCOG, ACOG): oxytocin 10 IU IM within 1 min after the birth of the baby, controlled cord traction, uterine massage after placental delivery. Reduces the risk of PPH by 60 %.

Why does the second stage of labor last longer with epidural anesthesia?
The pushing reflex and pelvic floor muscle tone are weakened. Normally — up to 1 h is added to the upper limit; up to 4 h in nulliparous and 3 h in multiparous women.

What is the Credé maneuver?
External uterine massage through the abdominal wall to express the separated placenta. Currently used less frequently due to the risk of trauma; controlled cord traction is preferred.

When is an episiotomy necessary?
Based on individual indications: risk of grade III-IV perineal laceration, severe fetal distress requiring rapid delivery, operative vaginal delivery. Not indicated routinely — ACOG/RCOG do not recommend it.

See also: Normal labor · Postpartum hemorrhage · Apgar score · Shoulder dystocia · Obstetrics catalog