OB | Labor Complications PRIMER

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1. Labor Mechanics and Dystocia Normal labor progression relies on the "Three Ps": Power (uterine contractions), Passenger (fetal size and presentation), and Passage (the maternal pelvis). Dystocia is an abnormal, slow progression of labor, broadly categorized into protraction (slower than normal) or arrest (complete cessation of progress) disorders. When labor stalls due to inadequate contractions, augmentation via amniotomy (rupturing the membranes) or intravenous oxytocin is used to stimulate progression. If the pelvis is inadequate or the fetus is severely malpositioned (e.g., breech or face presentation), a cesarean delivery is typically required to prevent injury.

2. Fetal Surveillance Electronic fetal monitoring evaluates fetal oxygenation and well-being. Fetal heart rate (FHR) tracings fall into three specific tiers:

• Category I (Normal): Baseline of 110-160 bpm, moderate variability, and no late or variable decelerations.
• Category II: Indeterminate tracings requiring continued surveillance.
• Category III (Abnormal): Absent variability coupled with recurrent late/variable decelerations or bradycardia. This indicates severe fetal hypoxia and often warrants immediate delivery. Deceleration patterns offer specific clues: early decelerations indicate benign fetal head compression, variable decelerations indicate umbilical cord compression, and late decelerations signal dangerous uteroplacental insufficiency.

3. Major Obstetric Emergencies

• Umbilical Cord Prolapse: The cord slips ahead of the fetus, causing severe cord compression. Providers must manually elevate the presenting part off the cord and immediately prepare for an emergency cesarean.
• Shoulder Dystocia: The fetal head delivers, but the anterior shoulder becomes trapped behind the pubic bone, often indicated by the "turtle sign". Crucial interventions include the McRoberts maneuver (hyperflexing maternal legs) and suprapubic pressure. Fundal pressure is strictly contraindicated as it worsens the impaction.
• Uterine Rupture & Placental Abruption: Rupture is a catastrophic tearing of the uterine wall, often at a prior cesarean scar. Abruption is the premature detachment of the placenta from the uterine wall. Both present with severe abdominal pain, fetal distress, and hemorrhage, requiring emergent surgery.
• Postpartum Hemorrhage (PPH): Defined as blood loss ≥1000 mL, primarily caused by the "4 Ts": Tone (uterine atony), Tissue (retained placenta), Trauma, and Thrombin (coagulopathy). First-line treatment focuses on fundal massage and uterotonic medications like oxytocin.

4. Preterm Labor Preterm labor involves regular contractions causing cervical change before 37 weeks' gestation. The primary goal is to delay delivery using tocolytics (such as magnesium sulfate or nifedipine) for at least 48 hours. This creates a critical window to administer corticosteroids (like betamethasone) to accelerate fetal lung maturity.

5. Early Pregnancy Complications Ectopic pregnancies occur when a fertilized egg implants outside the uterus, usually in the fallopian tube. They present with bleeding and abdominal pain, are diagnosed via ultrasound and rising hCG levels, and are treated medically with methotrexate or surgically. Spontaneous abortions (miscarriages) occur before 20 weeks and are managed expectantly, medically (e.g., misoprostol).