First stage of labor

First Stage of Labor - The Grand Opening

• Definition: Onset of regular uterine contractions to full cervical dilation (10 cm).
• Phases: Divided into Latent and Active phases based on the rate of cervical change.

• Latent Phase: Gradual, slow cervical change.
  • Dilation: 0 to <6 cm.
  • Contractions: Mild, often irregular.
• Active Phase: Rapid, predictable cervical dilation.
  • Dilation: ≥6 cm to 10 cm.
  • Dilation Rate: Nulliparous ≥1.2 cm/hr; Multiparous ≥1.5 cm/hr.
  • Contractions: Strong, regular (e.g., every 2-3 min).

📌 3 P's of Labor: Power (contractions), Passenger (fetus), Passage (pelvis).

⭐ Active phase protraction (slower-than-expected dilation) is a common indication for intervention, often with oxytocin, to prevent arrest of labor.

Labor Dystocia - When Things Slow Down

• Definition: Abnormally slow progression of labor, also known as "failure to progress."

• Etiology 📌 (The 3 Ps):

  • Power: Inadequate uterine contractions (< 200 Montevideo units).
  • Passenger: Fetal factors like macrosomia, malpresentation (e.g., occiput posterior), or malposition.
  • Passage: Pelvic anatomy limitations (cephalopelvic disproportion - CPD).

• Diagnosis (Active Phase >6 cm):

  • Protraction: Slower than expected dilation.
    • Nullipara: < 1.2 cm/hr
    • Multipara: < 1.5 cm/hr
  • Arrest: No cervical change despite:
    • ≥ 4 hours of adequate contractions.
    • ≥ 6 hours of inadequate contractions (requires oxytocin).

⭐ Before diagnosing arrest and proceeding to C-section, ensure at least 4-6 hours of observation with augmented labor (if needed). This avoids premature surgical intervention.

• Management:

Management - The Watchful Wait

• Maternal Monitoring:

  • Vitals & pain assessment: q 1-4 hrs.
  • Contractions: Palpation or tocometry for frequency, duration, strength.
  • Cervical exam: q 2-4 hrs in active phase to assess dilation, effacement, station. Avoid excessive exams to ↓ infection risk.

• Fetal Monitoring:

  • Intermittent auscultation or continuous electronic fetal monitoring (EFM).
  • Assess baseline FHR, variability, accelerations, and decelerations.

• Patient Support:

  • Encourage ambulation & position changes.
  • Maintain hydration (oral or IV).
  • Offer pain relief options (e.g., epidural).

⭐ Active Phase Progression: Expect cervical dilation of ≥ 1-2 cm/hr. Slower progression may indicate arrest of labor, requiring intervention like oxytocin.

High‑Yield Points - ⚡ Biggest Takeaways

• First stage of labor spans from the onset of regular contractions to full cervical dilation (10 cm).
• It comprises a latent phase (0-6 cm) and an active phase (6-10 cm).
• Prolonged latent phase is >20 hours (nulliparous) or >14 hours (multiparous); management is often rest.
• Active phase arrest-no cervical change for ≥4 hours with adequate contractions or ≥6 hours without-is a common reason for C-section.
• Always evaluate the 3 Ps (Power, Passenger, Passage) to diagnose labor abnormalities.