Placenta previa

Placenta Previa - Low-Lying Intruder

• Pathophysiology: Placenta implants over or near the internal cervical os. Types: complete, partial, marginal, or low-lying.
• Clinical Presentation: Sudden, painless, bright red vaginal bleeding, typically after 20 weeks gestation. Uterus is soft and non-tender.
• Risk Factors: Prior C-section, multiparity, advanced maternal age (>35), prior previa.
• Diagnosis & Management:
  • Transvaginal ultrasound is the gold standard for diagnosis.
  • ⚠️ NO digital vaginal or speculum exams.
  • C-section delivery is indicated, usually at 36-37 weeks.

⭐ The classic triad is painless bleeding, a soft non-tender uterus, and reassuring fetal heart tones. Absence of pain is a key feature distinguishing it from placental abruption.

Risk Factors & Presentation - Red Alert Antepartum

• Risk Factors:

  • Prior C-section or other uterine surgery
  • Multiparity & advanced maternal age (> 35 yrs)
  • Cocaine use or smoking
  • Prior placenta previa

• Clinical Picture:

  • Sudden, painless, bright red vaginal bleeding
  • Typically occurs after 28 weeks gestation
  • Uterus is soft, relaxed, and non-tender
  • Fetal heart tones usually reassuring initially

⭐ Warning: Digital or speculum vaginal examination is absolutely contraindicated as it can provoke catastrophic hemorrhage. Diagnosis is made by ultrasound.

Diagnosis - Ultrasound Unveiling

• Initial Test: Transabdominal ultrasound.
• Gold Standard: Transvaginal ultrasound (TVS) is safe & more accurate for precise localization.
• Follow-up: Repeat scan at ~32 weeks; many early previas resolve via "placental migration."

⭐ A digital vaginal exam is contraindicated if placenta previa is suspected until it has been ruled out by ultrasound.

Management - Watchful Waiting Game

• Indication: Preterm gestation (< 36-37 weeks) with a hemodynamically stable mother and reassuring fetal status.
• Core Strategy: Inpatient observation, especially after a bleeding episode.

• Key Interventions:
  • Corticosteroids (Betamethasone): Administer if gestational age is < 34 weeks to promote fetal lung maturity.
  • Strict Pelvic Rest: No vaginal exams (digital or speculum) and no intercourse.
  • Tocolysis (e.g., Magnesium Sulfate): ⚠️ Used cautiously for short-term uterine quiescence, primarily to allow corticosteroids to take effect.
  • Anemia Correction: Maintain maternal hematocrit > 30%.

⭐ Elective cesarean delivery is planned for 36 0/7 to 37 6/7 weeks, even in asymptomatic cases, to minimize the risk of hemorrhage from spontaneous labor.

Complications & Vasa Previa - Dangerous Liaisons

• Maternal: Risk of massive hemorrhage (may necessitate hysterectomy). Placenta accreta spectrum risk ↑ with prior C-sections.
• Fetal: Preterm birth, IUGR, and fetal anemia.
• Vasa Previa: A related emergency where unprotected fetal vessels run over the cervical os. Membrane rupture can tear these vessels, causing rapid fetal exsanguination.

⭐ Vasa Previa Triad: Rupture of membranes, painless vaginal bleeding, and subsequent fetal bradycardia or a sinusoidal heart rate pattern.

High‑Yield Points - ⚡ Biggest Takeaways

• Painless, bright red vaginal bleeding in the third trimester is the classic presentation.
• The placenta implants over or near the internal cervical os.
• Major risk factors include prior cesarean delivery, multiparity, and advanced maternal age.
• Transvaginal ultrasound is the gold standard for diagnosis; transabdominal is used for initial screening.
• Digital vaginal examination is absolutely contraindicated due to the risk of catastrophic hemorrhage.
• Management is typically a planned cesarean delivery at 36-37 weeks.