Engagement, Fingers, and Station in Labour

1. Definitions

Engagement

• Clinically: when the leading bony edge of the fetal head is at or below the level of the ischial spines (station 0), the head is engaged.
• On abdominal palpation (fifths above the brim): the head is engaged when ≤ 2/5 is palpable abdominally.
• On vaginal examination (fingers): engagement is inferred from station being 0 or positive.

Station

The contemporary ACOG/Williams system uses −5 to +5 (each centimetre from the spines). The older 3-tier system uses −3 to +3. Both are in use clinically; know which your institution employs.

"Number of Fingers" — Abdominal Assessment (Fifths)

2. Normal Progress: Phases of Labour and Expected Station

Phase 1 — Latent Phase (0–4 cm cervical dilation)

• Station: typically −3 to −1 (head may still be above the spines, especially in multigravidae)
• In primigravidae: engagement often occurs at 36–38 weeks gestation, before labour — so at the onset of latent labour the head is usually already at 0 or −1.
• In multigravidae: engagement often occurs only with onset of active labour or even during second stage.
• Abdominal finding: 2–3/5 palpable above brim; descent may not yet be occurring.

• A floating head (5/5 palpable, station −5) at the onset of regular contractions is abnormal in a primigravida → suspect CPD, malpresentation, or placenta praevia.
• If membranes rupture with a floating head → high risk of cord prolapse → emergency.

Phase 2 — Active Phase (4–10 cm, especially 6–10 cm)

• Friedman's active phase: cervix dilates ≥ 1 cm/hour (primigravida) or ≥ 1.5 cm/hour (multigravida); head descends simultaneously.
• Station progresses from ~−1 → 0 → +1 as active phase advances.
• By full dilation (10 cm): station should be 0 to +1 at minimum in most women; often +1 to +2 in multigravidae.

• 4 cm dilatation ≈ station −1 to 0
• 7 cm ≈ station 0 to +1
• 10 cm ≈ station +1 to +2

Phase 3 — Second Stage (Full dilation → delivery)

• Active pushing causes descent from ~+1 to +5 (crowning).
• Expected duration: up to 3 hours (primigravida with epidural) or 2 hours (without epidural); shorter for multigravida.
• Descent must occur continuously; station should advance with each pushing effort.

Phase 4 — Third Stage (Delivery of placenta)

• Station is no longer relevant; the pelvis is empty.

3. Indications to Intervene Based on Engagement and Station

A. Before/During Latent Phase

B. During Active Phase — Failure of Descent (Arrest of Descent)

C. During Second Stage — Criteria for Instrumental Delivery

1. Head must be engaged (station ≥ 0)
2. Presenting part must be at or below the spines
3. If head is at −1 or above → proceed to CS

D. Station and Cord Prolapse

• Cord prolapse occurs predominantly when the head is not engaged (station −1 or above)
• After SROM or ARM with station −2 or worse → digital VE mandatory → cord felt → immediate knee-chest position + emergency CS

E. Station and Obstructed Labour

• Caput succedaneum — oedematous swelling of scalp (makes station feel falsely low on VE)
• Moulding (grades 1–3) — overlapping of skull bones
• These may give a false impression of descent on VE while the bony head is not advancing — use both abdominal (fifths) and vaginal (station) assessments together

4. Summary Table: Phases, Expected Findings, and Trigger to Intervene

5. Clinical Pearls

• Never perform ARM when the head is floating (station −3 or above) — cord prolapse risk.
• Descent without dilation is abnormal and suggests a fetal or pelvic structural problem.
• Dilation without descent suggests the uterus is working but the head is not entering the pelvis — CPD or malposition until proven otherwise.
• In obstructed labour, the combination of prolonged second stage + caput + moulding + no change in abdominal fifths despite vaginal station appearing low = operative delivery (CS) — instrumental delivery is contraindicated.
• The partograph plots station and cervical dilation together over time; deviation from the alert line or action line in both axes triggers management decisions.

Clinical Scenario Analysis & Management

Parsing the Clinical Picture

The Core Conflict — Why This Scenario is a Trap

• Station −1 = head is still above the ischial spines
• 2/5 palpable abdominally = head is engaged (BPD through inlet), but the leading edge has not yet reached the spines
• Moulding grade 1 = early, not alarming on its own, but in context is significant

This head is not low enough for any instrumental delivery.

1. Station ≥ 0 (at or below the ischial spines) — this patient is at −1, i.e., above the spines
2. No significant CPD — moulding + station together suggest early obstruction

CTG Classification — What "Pathological" Means

The Answer: Emergency Caesarean Section (Category 1 CS)

Decision Rationale

Immediate Steps (Before and During CS)

1. Resuscitative Measures (In Parallel — Start NOW)

• Left lateral tilt or full left lateral position → relieve aortocaval compression
• High-flow oxygen (10–15 L/min via face mask) → increase maternal PaO₂
• Stop oxytocin if running → reduce uterine hyperstimulation
• IV access + fluid bolus → correct hypotension
• Tocolysis if uterine hyperstimulation contributing: Terbutaline 0.25 mg SC (or salbutamol IV) to relax the uterus and improve uteroplacental flow
• Call for help: senior obstetrician, anaesthetist, neonatologist/paediatrician

2. Consent and Preparation

• Informed consent for emergency CS (if patient can consent; otherwise document emergency)
• Blood group and crossmatch; baseline FBC, coagulation
• Bladder catheterisation in theatre

3. Anaesthesia

• Spinal anaesthesia preferred if time allows (faster and safer than GA)
• General anaesthesia if immediate delivery required (profoundly pathological CTG, maternal collapse)

4. Operative Consideration: "Push-Up" by Vaginal Assistant

• At CS when the head is at station −1, the surgeon will need a vaginal assistant to push the fetal head up out of the pelvis while the uterine incision is made — this is the standard technique when the head is low/engaged but not yet crowning

5. Neonatal Team

• Paediatrician at delivery for potential neonatal resuscitation
• Cord blood gases (arterial and venous) for documentation

Why NOT to Push / Wait

Summary

25-year-old primigravida, second stage of labour, station −1, pathological CTG → Emergency (Category 1) Caesarean Section.

Clinical Scenario Analysis

Parsing the Findings

The Key Decision Points

1. Is the fetus in a good condition?

• Clear liquor ✓
• No CTG abnormality mentioned ✓
• No moulding or caput ✓

2. Is instrumental delivery feasible?

3. Which instrument?

• The occiput is at the 3 o'clock position (transverse)
• Needs to rotate 45° → LOA and then to OA for delivery
• Total rotation required: ~90°

Best Management Option

Ventouse (Vacuum Extraction) — Instrument of Choice

1. Maternal exhaustion — a primary indication for vacuum extraction per Creasy & Resnik: "Maternal indication for shortening of the second stage of labor (e.g., cardiovascular or cerebrovascular disease, maternal exhaustion)"
2. Station +1 with no CPD — head is below the spines, no obstruction
3. Occipitolateral position — ventouse (unlike forceps) naturally encourages autorotation of the fetal head to OA as traction is applied. This is a major advantage over forceps in non-OA positions
4. No significant caput/moulding — low-risk for application; cup will sit correctly on the flexion point
5. Clear liquor, no fetal distress — not an emergency; a methodical vacuum delivery is appropriate
6. Ventouse is preferred over forceps in this scenario because:
   • Requires less analgesia
   • Allows the head to rotate naturally during traction
   • Less maternal pelvic floor trauma (Creasy & Resnik: "maternal complications… generally less frequent and less severe than those of forceps")
   • Easier to teach and apply safely

Step-by-Step Management

Before Application

1. Confirm full dilation on VE (already confirmed)
2. Confirm station and position — station +1, LOL
3. Inform and consent the patient
4. Adequate analgesia — pudendal block or perineal infiltration (epidural if already in situ)
5. Empty the bladder — in/out catheterisation
6. Senior obstetrician present; neonatal team on standby

Ventouse Application

1. Apply the posterior/Kiwi cup (or rigid posterior metal cup for mid-cavity LOT) at the flexion point — 3 cm anterior to the posterior fontanelle on the sagittal suture, not on the anterior fontanelle
2. Create vacuum: raise to 0.2 kg/cm² first → check no maternal tissue caught → raise to 0.8 kg/cm²
3. Traction with contractions and maternal pushing: downward and outward in the axis of the pelvis; the head will rotate from LOL → LOA → OA as it descends
4. Rule of 3s: max 3 pulls, 3 contractions, 3 cup detachments — if not delivering, abandon and reassess

Episiotomy

• Mediolateral episiotomy at crowning if perineal resistance is significant — not routine, but indicated if tissues tight or progress slow

After Delivery

• Inspect for perineal, vaginal, and cervical lacerations
• Active management of third stage (oxytocin 10 IU IM)
• Neonatal check — examine scalp for chignon, cephalohaematoma, subgaleal haemorrhage

What NOT to Do

Summary

29-year-old primigravida, 90 min in second stage, exhausted, station +1, LOL position, no CPD, reassuring fetal condition → Ventouse (vacuum extraction) delivery.

Clinical Scenario Analysis

Parsing the Findings

The Central Issue

How do you deliver safely knowing shoulder dystocia may recur — and what must you prepare for?

Recurrence Risk of Shoulder Dystocia

• Previous shoulder dystocia is one of the strongest risk factors for recurrence (Creasy & Resnik: "a history of shoulder dystocia in a previous birth" is a recognised risk factor)
• Recurrence rate: approximately 10–16% (some studies up to 25%)
• 50% of shoulder dystocia cases have no identifiable risk factors, but a prior history doubles to quadruples the baseline risk
• The severity of the previous episode and birth weight of the previous baby are important predictors

Next Step in Management

Controlled Vaginal Delivery with Full Preparation for Shoulder Dystocia

Creasy & Resnik: "Primary cesarean delivery can prevent shoulder dystocia in a small proportion of patients when several predisposing factors are present, such as multiparity, gestational diabetes, and an estimated fetal weight in excess of 4500 g" — implying that past shoulder dystocia alone is not sufficient to mandate CS.

Immediate Actions — Before and During Delivery

Step 1: Call for Help — NOW (Before the Head Delivers)

• Senior/experienced obstetrician at the bedside
• Midwife × 2 — one to apply suprapubic pressure, one to assist
• Anaesthetist — for emergency anaesthesia if needed
• Neonatologist/paediatrician — for neonatal resuscitation (risk of asphyxia and brachial plexus injury)
• Theatre team on standby (Zavanelli manoeuvre → CS in extremis)

Step 2: Brief the Team

• Announce: "This patient has a history of shoulder dystocia. We should anticipate and be ready."
• Assign roles: who applies suprapubic pressure, who will go vaginally, who is calling time intervals
• Have a wide episiotomy plan ready (to facilitate internal manoeuvres if needed)

Step 3: Consider Epidural/Adequate Anaesthesia

• If not already present, consider pudendal block or ensure adequate perineal analgesia
• Internal manoeuvres require the mother to be relaxed and cooperative

Step 4: Deliver the Head Carefully

• Avoid fundal pressure (worsens impaction)
• After the head delivers, pause and check for the "turtle sign" (head retracts back against the perineum after delivery — early warning of shoulder dystocia)
• Do NOT apply traction downward — wait and prepare

If Shoulder Dystocia Occurs — HELPERR Protocol (or ALARMER)

• Zavanelli manoeuvre: cephalic replacement into the uterus → emergency CS
• Deliberate clavicle fracture (rarely required)
• Symphysiotomy (rarely, in resource-limited settings)

Regarding Instrumental Delivery

• Station is +2 — the head is descending well; spontaneous vaginal delivery is preferred with active pushing
• If instrumental delivery is needed (fetal distress, prolonged second stage), it is not absolutely contraindicated — but the operator must be fully aware that applying traction with forceps/ventouse when shoulder dystocia occurs worsens brachial plexus injury; traction must stop immediately at the turtle sign

Summary Answer

The next step is: controlled vaginal delivery with full team preparation and anticipation of shoulder dystocia.

1. Call senior obstetrician, second midwife, anaesthetist, and neonatologist immediately — before delivery
2. Brief the team on shoulder dystocia risk and assign roles
3. Proceed with vaginal delivery — cervix fully dilated, station +2, no contraindication to vaginal birth
4. Deliver the head gently; watch for the turtle sign
5. If shoulder dystocia confirmed → execute HELPERR sequence without delay, starting with McRoberts + suprapubic pressure (resolves ~42–58% of cases), then internal manoeuvres, then delivery of the posterior arm
6. Do not apply fundal pressure; avoid aggressive downward traction on the fetal head
7. Neonatal team to receive baby — assess for brachial plexus injury, asphyxia, fractures