What is the assessment and management plan for vaginal bleeding in the 2nd (second) trimester?

Assessment and Management of Vaginal Bleeding in the Second Trimester

Transabdominal ultrasound is the preferred initial procedure for evaluation of second trimester vaginal bleeding, with transvaginal ultrasound frequently necessary if transabdominal views are inadequate or inconclusive. 1

Initial Assessment

Diagnostic Approach

• Immediate ultrasound evaluation is essential regardless of symptoms or β-hCG levels 1, 2
• Avoid digital pelvic examination until placenta previa, low-lying placenta, and vasa previa have been excluded 1
• Distinguish between painless and painful bleeding, as this helps narrow differential diagnosis 1

Key Ultrasound Components

1. Transabdominal ultrasound (first-line):

   • Evaluate placental location and relationship to cervix
   • Assess fetal viability
   • Look for evidence of placental abruption (clot)
   • Check for free fluid in pelvis
   • Evaluate cervical length and status

2. Transvaginal ultrasound (when needed):

   • More accurate assessment of placental relationship to cervix
   • Better visualization of cervix from external to internal os
   • More sensitive for detecting placental abruption
   • Can detect vasa previa with greater accuracy
   • Measurement of placental overlap of internal os (>15mm at mid-trimester suggests persistent previa) 1

Common Causes and Management

Painless Bleeding

1. Placenta Previa

   • Most common diagnosis (1 in 200 pregnancies) 1
   • Management:
     • Pelvic rest (no intercourse or vaginal exams)
     • Hospitalization for significant bleeding
     • Serial ultrasound monitoring (placental position may change)
     • Preparation for possible cesarean delivery

2. Low-lying Placenta

   • Management similar to placenta previa but less restrictive if minimal bleeding
   • Follow-up ultrasound to assess placental migration

3. Vasa Previa

   • Rare (1 in 2,500-5,000 deliveries) but potentially fatal to fetus 1
   • Requires color Doppler ultrasound for diagnosis
   • Management includes hospitalization, close monitoring, and planned cesarean delivery

Painful Bleeding

1. Placental Abruption

   • Affects approximately 1% of pregnancies 1
   • Ultrasound sensitivity is limited (detects at most 50% of cases) 1
   • Management:
     • Continuous fetal monitoring
     • Preparation for emergency delivery if significant abruption
     • Assessment of maternal hemodynamic status and coagulation

2. Preterm Labor

   • Evaluate cervical length via transvaginal ultrasound
   • Bleeding with short cervix significantly increases preterm delivery risk 1

3. Uterine Rupture

   • Rare but serious, especially with history of cesarean delivery
   • Ultrasound may show disruption of myometrium
   • Lower uterine segment thickness <2.5mm predicts uterine dehiscence 1

Special Considerations

Role of Doppler Ultrasound

• Essential for diagnosis of vasa previa
• Helpful in distinguishing placental tissue from blood clot in suspected abruption
• Can identify vessels overlying internal cervical os 1

Prognostic Factors

• Abnormal ultrasound findings significantly increase risk of:
  • Preterm delivery (RR 2.0)
  • Fetal death (RR 2.6)
  • Perinatal death (RR 2.6) 3
• Second trimester bleeding with abnormal ultrasound findings has perinatal mortality rate of 258:1000 3

Hospitalization Criteria

• Significant bleeding
• Placenta previa with active bleeding
• Placental abruption
• Signs of preterm labor
• Hemodynamic instability 1, 2

Common Pitfalls to Avoid

• Performing digital pelvic examination before ruling out placenta previa 1, 2
• Underestimating significance of bleeding, even if minimal
• Failing to use transvaginal ultrasound when transabdominal views are inadequate
• Discharging patients without definitive diagnosis of bleeding source
• Neglecting to administer Rh immunoglobulin to Rh-negative women with bleeding 2

Second trimester vaginal bleeding requires prompt and thorough evaluation as it is associated with significant maternal and fetal risks. The appropriate use of ultrasound is essential for accurate diagnosis and management planning.