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Preterm Labor and Delivery

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PTL: Definition & Risks - Defining Danger

  • Definition: Regular uterine contractions + cervical changes (dilatation/effacement) at Gestational Age (GA) < 37 0/7 weeks.
  • Key Risk Factors:
    • Previous preterm birth (PTB).
    • Multiple gestation (twins, triplets).
    • Infections (e.g., UTI, BV).
    • Preterm Prelabor Rupture of Membranes (PPROM).
    • Cervical incompetence / short cervix (< 25 mm mid-trimester).
    • Uterine overdistension (polyhydramnios).
    • Placental issues (abruption, previa).
    • Maternal: smoking, extremes of age, low SES.

⭐ Strongest risk factor for PTL is a history of prior spontaneous preterm birth.

PTL: Diagnosis & Prediction - Catching It Quick

  • Clinical Diagnosis:

    • Uterine contractions: ≥4 in 20 min or ≥8 in 60 min
    • AND Documented cervical change:
      • Dilatation ≥2 cm
      • Effacement ≥80%
      • Cervical length (CL) <25mm via TVS
  • Prediction Markers:

    • History: Prior PTL (strongest predictor).
    • Biochemical Markers:
      • fFN: Positive if >50 ng/mL (22-34 wks).
      • PIGFBP-1.
      • PAMG-1.
    • Biophysical:
      • TVS Cervical Length (CL): <25mm (16-24 wks) indicates ↑ risk. Transvaginal ultrasound: Short cervical length

⭐ Negative fFN test: High NPV (97-99%) for ruling out delivery within 7-14 days.

PTL: Tocolysis - Hitting Pause

📌 Mnemonic: 'It''s Not My Time' (Indomethacin, Nifedipine, Magnesium Sulfate, Terbutaline/Atosiban)

Tocolytics Comparison:

TocolyticMOADose (Brief)Key SEsKey CIs / GA Limit
Indomethacin↓PG synthLoad; ≤48hPDA closure, Oligo32 wks, NSAID allergy
NifedipineCa²⁺ Blocker10-20mg POHypotension, HeadacheCardiac dz, Hypotension
$MgSO_4$Ca²⁺ Antag.IV Load+Maint.Flushing, Resp. dep.Myasthenia, Renal fail.
Terbutalineβ₂-Agonist0.25mg SCTachycardia, Pulm. edemaCardiac dz, Uncontrolled DM
AtosibanOxytocin Antag.IV Bolus+Inf.Nausea, Headache (mild)Allergy

⭐ > First-line tocolytic for GA <32 weeks is Indomethacin, but it's contraindicated after 32 weeks due to risk of premature ductus arteriosus closure.

PTL: Fetal Care & Prevention - Guarding Futures

  • Antenatal Corticosteroids (ACS): Fetal lung maturity; PTL 24-34 wks.
    DrugRegimen
    Betamethasone12 mg IM, 2 doses 24 hrs apart
    Dexamethasone6 mg IM, 4 doses 12 hrs apart
  • Magnesium Sulfate ($MgSO_4$): Neuroprotection <32 wks GA.
  • Prevention Strategies:
    • Progesterone (vaginal/IM): Prior PTL or short cervix (<25 mm).
    • Cervical Cerclage: History-indicated (prior PTL) or USG-indicated short cervix. Cerclage: Preventing Premature Birth

⭐ ACS significantly reduces risks of Respiratory Distress Syndrome (RDS), Intraventricular Hemorrhage (IVH), and Necrotizing Enterocolitis (NEC) in preterm neonates.

High‑Yield Points - ⚡ Biggest Takeaways

  • Preterm labor: Regular contractions with cervical changes from 20 to <37 weeks gestation.
  • Fetal fibronectin (fFN): High negative predictive value for ruling out imminent preterm delivery.
  • Cervical length <25 mm on TVS is a major risk factor for preterm birth.
  • Tocolytics (e.g., Nifedipine) delay delivery for 48 hours to allow corticosteroid administration.
  • Antenatal corticosteroids (Betamethasone) are crucial for fetal lung maturity if <34 weeks.
  • Magnesium sulfate offers neuroprotection for fetuses delivered <32 weeks.

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