Preterm labor is defined as onset of labor before 37 weeks of gestation, leading to preterm birth.
Classification of Preterm Birth:
- Extremely Preterm: <28 weeks
- Very Preterm: 28–32 weeks
- Moderate to Late Preterm: 32–37 weeks
Etiology (Causes) of Preterm Labor
Maternal Causes:
- Previous preterm birth
- Short cervical length (<25 mm)
- Infections (UTI, Chorioamnionitis, Bacterial vaginosis)
- Multiple pregnancies (Twins, Triplets)
- Uterine anomalies (Fibroids, Septate uterus)
- Smoking, Substance abuse
- Polyhydramnios
Fetal Causes:
- Fetal distress (IUGR, Fetal anomalies)
- Multiple pregnancy
Placental Causes:
- Placental abruption
- Placenta previa
Clinical Features of Preterm Labor
- Uterine contractions (>4 in 20 minutes or >8 in 60 minutes).
- Cervical changes (Effacement & Dilatation).
- Lower abdominal pain, Pelvic pressure.
- Increased vaginal discharge or rupture of membranes (PROM).
Diagnosis of Preterm Labor
1. Clinical Assessment:
- Uterine contractions + Cervical changes.
2. Investigations:
- Transvaginal Ultrasound (TVS):
- Cervical length <25 mm → High risk for preterm labor.
- Fetal Fibronectin (fFN) Test:
- Positive → High risk of preterm delivery.
- CTG (Cardiotocography):
- Fetal well-being assessment.
- Urine & Vaginal Culture:
- Check for infections (UTI, Chorioamnionitis).
Management of Preterm Labor
1. Tocolysis (Contraction Suppression):
Used if labor is not advanced and there are no contraindications.
- First-line:
- Nifedipine (Calcium Channel Blocker) – 20 mg oral loading dose, then 10 mg q6h.
- Alternatives:
- Indomethacin (NSAID, <32 weeks only).
- Terbutaline (Beta-agonist).
- Magnesium sulfate (Also for fetal neuroprotection at <32 weeks).
Contraindications for Tocolysis:
- Severe preeclampsia/eclampsia.
- Fetal distress.
- Chorioamnionitis.
2. Corticosteroids (Fetal Lung Maturity):
- Indicated if <34 weeks gestation.
- Drugs:
- Betamethasone 12 mg IM every 24 hours (2 doses).
- Dexamethasone 6 mg IM every 12 hours (4 doses).
Benefits:
- Reduces risk of neonatal respiratory distress syndrome (RDS).
- Decreases incidence of intraventricular hemorrhage (IVH).
3. Magnesium Sulfate (Neuroprotection):
- Given at <32 weeks gestation.
- Protects against cerebral palsy in preterm infants.
- Dose:
- Loading: 4 g IV over 30 minutes.
- Maintenance: 1 g/hour for 24 hours.
4. Antibiotics (For PPROM Cases):
- Indications: Preterm Premature Rupture of Membranes (PPROM).
- Drugs:
- Ampicillin + Erythromycin for 7 days.
5. Delivery Plan
- If labor progresses → Allow vaginal delivery if possible.
- Indications for C-section:
- Malpresentation (Breech, Transverse lie).
- Fetal distress.
Complications of Preterm Birth
Neonatal Complications:
- Respiratory Distress Syndrome (RDS).
- Intraventricular Hemorrhage (IVH).
- Necrotizing Enterocolitis (NEC).
- Sepsis.
- Long-term Neurodevelopmental Delay.
Maternal Complications:
- Increased risk of PPROM & Chorioamnionitis.
- Psychological stress & Anxiety.
Summary Table: Preterm Labor
|
Feature |
Key Points |
|
Definition |
Labor before 37 weeks gestation |
|
Risk Factors |
Short cervix, Multiple pregnancy, Infection |
|
Diagnosis |
TVS (Cervical length <25 mm), fFN Test |
|
Treatment |
Tocolysis (Nifedipine), Steroids (Betamethasone),
Magnesium sulfate |
|
Complications |
RDS, IVH, NEC, Neurodevelopmental delay |
Key Takeaways
- Preterm labor is the leading cause of neonatal morbidity & mortality.
- Tocolytics delay labor but do not prevent it.
- Steroids & Magnesium sulfate improve fetal outcomes.
- Antibiotics are given in cases of PPROM.
