Antepartum Hemorrhage

Antepartum Hemorrhage
Anne Kennedy, MD
DIFFERENTIAL DIAGNOSIS
Common
  • Placental Abruption
  • Placenta Previa
  • Marginal Sinus Previa
Less Common
  • Placenta Accreta Spectrum
Rare but Important
  • Vasa Previa
ESSENTIAL INFORMATION
Key Differential Diagnosis Issues
  • Defined as vaginal bleeding from 28 weeks gestation until term
    • Many cases are idiopathic, though most likely from placental bed
    • Non-placental causes (e.g., cervicitis, severe monilial infection) should be apparent on clinical evaluation
      • Typically lighter bleeding (e.g., smear of blood-stained mucus)
  • Evaluation of placental location is important part of every obstetric scan
  • Scan technique important for correct diagnosis
    • Must see placenta and internal os in same image
    • If fetal parts or maternal habitus preclude visualization abdominally, perform transvaginal (TV) scans
      • Most effective method to visualize cervix
    • In patients with ruptured membranes translabial (transperineal) scanning may be helpful
  • Scan from side to side and anterior to posterior
    • Lateral wrap placentae may have low-lying/marginal insertion, which is not apparent on a true midline image
    • Use color Doppler to evaluate for vasa previa
  • Beware of full bladder, focal myometrial contraction
    • Spurious elongation of “cervix” → incorrect diagnosis of placenta previa
  • If low-lying placenta seen at mid-trimester scan, re-image at 32-34 weeks with TV technique
    • 5% of women have a low-lying placenta at 18 weeks
    • ˜ 1% of them have placenta previa at term
Helpful Clues for Common Diagnoses
  • Placental Abruption
    • Abdominal pain, dark red vaginal bleeding
    • Look for hypoechoic blood clot near or behind placenta
    • Marginal
      • Hemorrhage from edge of placenta
      • Can see raised edge in 50%
      • Curvilinear clot near placenta
      • Hemorrhage dissects under chorionic membrane → clot at a distance from placenta, look in front of cervical os
    • Retroplacental
      • Central hematoma between placenta and uterus
      • Large detachment more likely than with marginal abruption → ↑ risk of fetal morbidity
      • Appears acutely as “placentomegaly”
      • Power Doppler delineates clot from placenta
    • Preplacental
      • Hematoma on fetal surface of placenta
      • Clot may compress cord
  • Placenta Previa
    • Painless, bright red vaginal bleeding
    • Symmetric complete placenta previa
      • Placenta centrally implanted on cervix
      • Will not resolve with advancing pregnancy
    • Asymmetric complete placenta previa
      • Small part of placenta crosses internal os
      • May resolve with advancing pregnancy
      • If > 15 mm crosses internal os then less likely to resolve
    • Marginal: Placental edge within 2 cm of internal os
      • Gestational age > 20 weeks, TVUS done for maximal resolution
    • Low-lying placenta
      • Preferred term if < 20 wks and TVUS not done
      • Asymptomatic, majority resolve by 34 weeks
  • Marginal Sinus Previa
    • Maternal placental veins at edge of solid placenta, near or cross internal os
    • Do not confuse with vasa previa (fetal vessels in membranes anterior to internal os)
Helpful Clues for Less Common Diagnoses
  • Placenta Accreta Spectrum
    • Abnormal penetration of placental tissue beyond endometrial lining of uterus
    • Look for
      • Loss of subplacental hypoechoic zone
      • Placental sonolucencies (“swiss cheese appearance”)
      • Abnormal vascularity of placenta (“tornado vessels”)
      • Breach of bladder mucosa seen as defect in echogenic line
      • Use Doppler to look for large vessels in bladder wall
    • Some series claim better resolution with MR
      • May be helpful to look for spread into broad ligament
      • Also helpful if there’s history of other surgery that increases risk (e.g., posterior myomectomy)
    • MR technique
      • Fast T2 weighted sequences
      • Full bladder
      • Surgilube in vagina
      • Gadolinium not necessary (contraindicated in pregnancy)
    • Risk factors
      • Reported 5% risk with placenta previa, no prior C-section
      • 10% of patients with > 4 cesarean sections and no previa
      • 67% if previa and 4 prior C-sections
      • Prior uterine instrumentation
Helpful Clues for Rare Diagnoses
  • Vasa Previa
    • Fetal vessels running in membranes crossing the internal cervical os
    • Risk factors include
      • Placenta previa or low-lying placenta earlier in pregnancy
      • Multiple gestation
      • Succenturiate lobe
      • Low-lying placenta
    • Use transvaginal sonography and Doppler
    • Fetal arterial pulse confirms diagnosis
    • Indication for C-section prior to onset of labor
      • If spontaneous rupture of membranes tears fetal vessels, fetal exsanguination ensues
Other Essential Information
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Aug 10, 2016 | Posted by in OBSTETRICS | Comments Off on Antepartum Hemorrhage

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