Normal Labor Mechanism & WHO Intrapartum Care Guidelines

The "3 Ps" - Determinants of Labor

1. Powers - uterine contractions (frequency, intensity, duration)
2. Passenger - fetal size, position, and attitude (flexion/extension)
3. Passage - bony pelvis dimensions, shape, and pelvic floor soft tissue resistance

• Creasy & Resnik's Maternal-Fetal Medicine, p. 817

Stages of Labor

• Textbook of Family Medicine 9e, p. 502

First Stage of Labor

Latent Phase

• Variable in length: up to 20 hours in nulliparas, 14 hours in multiparas
• Minimal cervical dilation; cervix softens, effaces, and moves anterior
• Irregular, often painless contractions
• Mean cervical dilation in last 3 days before labor: ~1.8 cm (nulliparas), 2.2 cm (multiparas)

Active Phase

• Begins at approximately 5 cm dilatation (updated from the older Friedman threshold of 3-4 cm)
• Rapid cervical dilatation phase
• Classical Friedman minimum rates: ≥1.2 cm/hr (nulliparas), ≥1.5 cm/hr (multiparas)
• Contractions: every 2-3 minutes, ~60 seconds duration, ~40 mmHg intensity

Second Stage

• From full cervical dilatation to delivery of the baby
• Average duration: ~50 minutes in nulliparas, ~20 minutes in multiparas
• Woman has an involuntary urge to bear down with contractions
• Maternal expulsive forces combine with uterine contractions to drive descent

Third Stage

• Delivery of the placenta
• Signs of placental separation: lengthening of the cord, gush of blood, change in uterine fundal contour
• Normally completed within 30 minutes

Cardinal Movements of Labor (Vertex Presentation - LOA/OA)

1. Engagement

• The widest diameter of the fetal head (biparietal diameter, ~9.5 cm) descends below the plane of the pelvic inlet
• In nulliparas, often occurs 2-4 weeks before labor ("lightening")
• In multiparas, may not occur until labor begins
• Presenting diameter in well-flexed OA position is the suboccipitobregmatic (~9.5 cm)

2. Descent

• Progressive downward movement of the fetal presenting part through the pelvis
• Begins before engagement and continues throughout labor
• Driven by uterine contraction pressure, amniotic fluid pressure, and maternal bearing-down efforts
• Rate accelerates in late first stage and continues linearly into second stage

3. Flexion

• As the head meets resistance from the pelvic floor, flexion increases
• Chin tucks onto the chest
• Converts the presenting diameter from the larger occipitofrontal (~11.5 cm) to the smaller suboccipitobregmatic (~9.5 cm)
• Facilitates easier passage through the pelvis

4. Internal Rotation

• The occiput (and fetal head) rotates from the transverse or oblique position to the occiput anterior (OA) position under the pubic symphysis
• This aligns the longest fetal head diameter with the longest pelvic diameter at each level:
  • Pelvic inlet: widest transversely
  • Midpelvis: widest anteroposteriorly
• Driven by the levator ani and pelvic floor musculature

5. Extension

• After internal rotation, the occiput reaches the pubic symphysis
• The head extends (pivots around the subpubic arch) as the occiput, bregma, forehead, nose, mouth, and chin deliver successively over the perineum
• The suboccipital region becomes the fulcrum against the pubic arch

6. External Rotation (Restitution)

• Immediately after the head is born, it rotates back to its natural alignment with the fetal shoulders (which are still in the oblique pelvic diameter)
• Restitution: the head turns to the side it was originally facing
• Full external rotation: the occiput turns further toward the maternal thigh, bringing the shoulders into the AP diameter

7. Expulsion

• With the next contraction, the anterior shoulder delivers under the pubic symphysis with gentle downward traction
• Then the posterior shoulder follows with gentle upward traction
• The body follows rapidly with the next contraction
• Roberts and Hedges' Clinical Procedures in Emergency Medicine, p. 3449-3474
• Tintinalli's Emergency Medicine, p. 2011-2014

WHO Intrapartum Care Guidelines 2018 (Key Recommendations)

Care Throughout Labor and Birth

First Stage - Assessment and Progress

First Stage - Interventions

Second Stage

Third Stage

Summary: Key WHO Paradigm Shifts (2018)

1. Active phase now begins at 5 cm - not 3-4 cm (Friedman era). Slow progress before 5 cm should not prompt intervention.
2. 1 cm/hr progress rule is abandoned as the sole criterion for normal labor - do not intervene on this alone.
3. Intermittent auscultation over continuous CTG in healthy, low-risk laboring women.
4. No routine episiotomy, no fundal pressure, no amniotomy purely to shorten labor.
5. Woman-centred care: choice of position, companion, mobility, oral intake, pain relief options are all rights-based recommendations.
6. Delayed cord clamping ≥1 minute is standard care for all births.

Open Cesarean Section Wound Care

1. Background: Why C-Section Wounds Break Down

• Creasy & Resnik's Maternal-Fetal Medicine, p. 3771

2. Initial Assessment of the Open/Dehisced Wound

• Extent of separation - probe the wound edges with a sterile swab to determine depth and width
• Fascial integrity - most important step. Is fascia intact? Complete fascial disruption = surgical emergency
• Signs of infection: erythema, warmth, induration, purulent discharge, fever, malodor
• Devitalized/necrotic tissue requiring debridement
• Seromas/hematomas - may extend further subcutaneously than the visible opening
• Necrotizing fasciitis - rapidly spreading cellulitis with systemic toxicity; immediate surgical debridement required

3. Management Algorithm

Open C-section wound
        |
        ├──> Fascial disruption? → YES → Surgical emergency: explore + repair fascia
        |                                  (skin may be left open or closed)
        |
        └──> Fascia intact? → Proceed with conservative wound management
                    |
                    ├──> Infected? → Cultures + broad-spectrum antibiotics
                    |               + debridement + irrigation + open packing
                    |
                    ├──> Seroma/Hematoma? → Open/drain if large; observe if small
                    |
                    └──> Clean open wound → Moist wound healing
                                           → NPWT if large/deep
                                           → Delayed primary closure when ready

4. Step-by-Step Wound Care

Step 1: Open and Explore

• Remove sutures or staples along the separation
• Open the wound sufficiently to allow inspection and treatment
• Drain any collection (seroma, hematoma, pus)
• Obtain wound swab for culture and sensitivity

Step 2: Debridement

• Remove all devitalized, necrotic, and sloughy tissue
• Sharp debridement (forceps + scissors/scalpel) is the gold standard
• Enzymatic debridement (e.g., collagenase ointment) can supplement for persistent slough
• Autolytic debridement occurs under moist dressings (slower but suitable for shallow wounds)
• Goal: a clean wound base with healthy granulation tissue

Step 3: Irrigation

• Irrigate with warm saline or clean water at low pressure
• Reduces bacterial load effectively
• Do NOT use hydrogen peroxide, povidone-iodine, or hypochlorite solutions in open wounds - these damage granulation tissue and delay healing
• Repeat irrigation at every dressing change
• Showering is equally effective and should be encouraged

Step 4: Dressing Selection by Wound Stage

• Moist wound environment promotes faster re-epithelialization (vs. dry gauze)
• Non-adherent layers prevent trauma at dressing change
• Change frequency depends on exudate level - heavily exuding wounds: every 24-48 hrs; granulating wounds: every 2-3 days

Step 5: Antibiotics (if infected)

• Broad-spectrum coverage required - organisms can originate from skin, genitourinary tract, or GI tract
• Typical empirical regimen: amoxicillin-clavulanate OR cephalexin + metronidazole
• If MRSA suspected (hospital-acquired, prior MRSA): add trimethoprim-sulfamethoxazole or doxycycline
• Adjust based on culture results
• Duration: 5-7 days for superficial SSI; longer for deep infections

5. Negative Pressure Wound Therapy (NPWT / VAC)

• Stimulate granulation tissue formation
• Reduce local oedema and tissue exudate
• Reduce bacterial load
• Draw wound edges together

• Large or deep wounds not amenable to simple packing
• Wounds with significant dead space
• Obese patients with pannus (particularly high risk for wound breakdown)
• Wounds failing to granulate with conventional dressing

• Bailey and Love's Short Practice of Surgery 28e, p. 2851
• Creasy & Resnik's Maternal-Fetal Medicine, p. 4056

6. Closure Options

Secondary Intention (Healing Naturally)

• The wound is left open and granulates progressively from the base upward
• Suitable for small, shallow wounds or heavily infected wounds
• Requires daily dressing changes over weeks
• Results in wider scar but avoids re-infection risk

Delayed Primary Closure (DPC)

• Open packing for 3-5 days until wound is clean and granulating
• Then close the wound with sutures/staples
• Shown to significantly reduce wound infection rates and mean healing time
• Suitable for contaminated but not infected wounds once bacterial load is reduced

Secondary Closure (Late Suturing)

• After full granulation tissue has formed (weeks later)
• Used for larger wounds where simple DPC is not possible
• May require a minor procedure under local anesthesia

7. Monitoring and Follow-Up

8. Promoting Healing: General Measures

9. Summary Table - Quick Reference