Labor is the series of physiological events that result in the expulsion of the fetus, placenta, and membranes from the uterus through the birth canal. Normal labor (Eutocia) occurs when:
- Spontaneous in onset
- Fetus presents with vertex
- Completed within a reasonable time
- Without maternal or fetal complications
Mechanism of Labor
Labor occurs due to a combination of maternal and fetal factors, including hormonal, mechanical, and biochemical changes that lead to uterine contractions and cervical effacement.
Causes of Onset of Labor
- Hormonal Factors:
- Increased estrogen & prostaglandins → Promote uterine contractions.
- Decreased progesterone → Allows contractions to begin.
- Oxytocin Release → Stimulates contractions.
- Mechanical Factors:
- Overdistension of the uterus (especially in multiple pregnancy).
- Fetal pressure on the cervix → Leads to the Ferguson reflex, which stimulates oxytocin release.
- Fetal Contributions:
- Increased cortisol production from the fetus initiates labor.
Stages of Labor
Labor is divided into four stages:
1st Stage: Cervical Dilatation & Effacement
- Begins: Onset of regular contractions
- Ends: Full cervical dilatation (10 cm)
- Duration:
- Primigravida: 8–12 hours
- Multigravida: 6–8 hours
Phases of the First Stage:
- Latent Phase (0–4 cm dilatation):
- Slow cervical dilatation.
- Mild, irregular contractions (last 6–8 hours).
- Active Phase (4–10 cm dilatation):
- Rapid cervical dilatation.
- Strong, frequent contractions.
2nd Stage: Expulsion of the Fetus
- Begins: Full cervical dilatation (10 cm)
- Ends: Delivery of the baby
- Duration:
- Primigravida: 1–2 hours
- Multigravida: 30 minutes to 1 hour
- Fetal descent and expulsion occur due to strong uterine contractions, voluntary maternal pushing (bearing down), and the fetal movements in the birth canal.
3rd Stage: Placental Delivery
- Begins: Delivery of the baby
- Ends: Expulsion of the placenta and membranes
- Duration: 5–15 minutes
Mechanisms of Placental Separation:
- Schultze Method (80% cases): Placenta separates from center to periphery, delivered fetal side first.
- Matthews Duncan Method (20% cases): Placenta separates from one edge, delivered maternal side first.
4th Stage: Immediate Postpartum Period
- Begins: Expulsion of placenta
- Ends: 1 hour post-delivery
- Monitoring for:
- Uterine contraction (to prevent postpartum hemorrhage).
- Maternal vitals (BP, pulse, bleeding assessment).
Signs of True vs. False Labor
Feature | True Labor | False Labor (Braxton Hicks) |
Contraction Pattern | Regular, increasing intensity | Irregular, weak |
Pain Location | Starts in back, radiates to abdomen | Only in lower abdomen |
Effect of Walking | Intensifies contractions | Relieves contractions |
Cervical Changes | Effacement & Dilatation | No cervical changes |
Show (Blood-stained mucus) | Present | Absent |
Mechanism of Normal Labor (Cardinal Movements of Labor)
The fetus undergoes seven cardinal movements to navigate through the maternal pelvis:
- Engagement – Biparietal diameter of fetal head enters the pelvic inlet.
- Descent – Downward movement of the fetal head through the birth canal.
- Flexion – Chin moves towards the chest, reducing head diameter.
- Internal Rotation – Head rotates to align with the maternal pelvis.
- Extension – Head passes under the pubic symphysis and is delivered.
- Restitution – Head rotates back to its original position.
- External Rotation – Shoulders align with the maternal pelvis for delivery.
Management of Normal Labor
First Stage Management
- Assess uterine contractions every 30 minutes.
- Monitor fetal heart rate every 30 minutes (low risk) or every 15 minutes (high risk).
- Vaginal examination every 4 hours to assess cervical progress.
- Encourage fluids & mobility.
- Pain relief options:
- Non-pharmacological: Breathing exercises, massage.
- Pharmacological: Epidural, opioids.
Second Stage Management
- Assist maternal pushing efforts.
- Monitor fetal heart rate every 5 minutes.
- Episiotomy (if needed) to widen the vaginal opening.
- Controlled delivery of head to prevent perineal trauma.
Third Stage Management (Active Management of Third Stage of Labor - AMTSL)
- Oxytocin administration (10 IU IM or IV) immediately after birth.
- Controlled cord traction (Brandt-Andrews method) to aid placental expulsion.
- Uterine massage after placental delivery to prevent hemorrhage.
Fourth Stage Management
- Monitor maternal vitals every 15 minutes for 1 hour.
- Assess uterine tone & vaginal bleeding to prevent postpartum hemorrhage (PPH).
- Encourage early breastfeeding to promote oxytocin release.
Normal Labor: Summary Table
Stage | Begins With | Ends With | Duration |
First Stage | Onset of contractions | Full cervical dilatation (10 cm) | 6–12 hours |
Second Stage | Full cervical dilatation | Delivery of baby | 30 min – 2 hours |
Third Stage | Delivery of baby | Placental expulsion | 5–15 minutes |
Fourth Stage | Placental expulsion | 1 hour post-delivery | 1 hour |
.jpeg)