Latest SMFM Guidelines: Third Trimester Bleeding Between 34w0d and 36w6d Gestation

SUMMARY:

SMFM provides guidance on the management of patients who present with bleeding in the late preterm period (34w0d to 36w6d).  The following are the key highlights and recommendations:

Placenta Previa

  • Stable and no other obstetric complications: Deliver between 36w0d to 37w6d (Grade1B)
  • Mild late preterm bleeding with 1 or more prior bleeding episodes that occurred <34 weeks of gestation: Consider delivery due to risk of recurrent bleeding
  • Mild bleeding 34 to 35 weeks with resolution by time of evaluation: Management is less clear
  • Do not perform routine cervical length screening to determine who will bleed in late preterm period as data in limited on appropriate management (Grade 2C)

Placenta Accreta

  • Definition: Abnormal trophoblast infiltration beyond the fibrinoid Nitabuch layer
    • Placenta increta: Placenta invades myometrium
    • Placenta percreta: Placenta invades beyond the myometrium
  • Incidence: <1% (in absence of placenta previa unless > 5 prior cesareans
  • Risk factors
    • Placenta previa and previous cesarean (most common)
    • Uterine surgery | Advanced maternal age | Smoking | Multiparity
  • Stable: Deliver between 34 to 37 weeks (Grade 1C)
    • If patient is stable, it is reasonable to briefly delay delivery to coordinate requisite multidisciplinary team
  • ACOG/SMFM recommendations (2019)
    • Delivery for suspected accreta, increta or percreta at 34w0d to 35w6d

Vasa Previa

  • Definition: Placental implantation that overlies or abuts the internal cervical os
  • Presentation: Painless bleeding
  • Incidence
    • Seen in 1 to 4% of second trimester ultrasound exams
    • 10 to 20% of previas diagnosed at 20 weeks gestation will remain a previa in the late 3rd trimester
  • Stable: Deliver between 34 to 37 weeks (Grade 1C)

Placental Abruption

  • Definition: Placental separation, either partial or complete, prior to delivery
  • Incidence: 0.5 to 1%
  • Classic presentation
    • Abdominal pain and bleeding
    • Nonreassuring fetal heart rate tracing (approximately 60%)
  • Risk factors: Hypertension | Smoking | PPROM | Cocaine abuse | Uterine myomas, and previous abruption
  • No clinical trials regarding ideal timing for delivery
    • Stable with high clinical index of suspicion: Delivery in late preterm or early term (expert opinion)
    • Diagnosis unclear, minimal bleeding, both mother and fetus stable: Delivery may be delayed with close surveillance and ongoing fetal testing
    • Active bleeding: Delivery as with any other active hemorrhage case

KEY POINTS:

Delivery Considerations

  • If patient actively bleeding, delivery is indicated if the following are present
    • Significant vaginal bleeding
    • Abnormal laboratory results including such as acute anemia or coagulopathy
    • Abnormal fetal heart tracing
    • Maternal status unstable
  • If actively hemorrhaging, do not delay delivery for purpose of administering antenatal corticosteroids (Grade 1B)
  • Do not perform fetal lung maturity testing in late preterm period to guide management if there is an indication for delivery (Grade 1B)
  • Administer antenatal corticosteroids if (Grade 1A)
    • Delivery expected within 7 days
    • Gestational age is between 34w0d to 36w6d
    • Antenatal corticosteroids have not previously been administered
  • Cesarean section for placenta previa, vasa previa or accreta
    • For other clinical scenarios, vaginal delivery may be appropriate if
      • No contraindication for vaginal delivery
      • Fetal status is stable
    • Small amount of late preterm bleeding that has resolved by the time the patient presents may be treated expectantly if the following conditions met (no evidence-based recommendations currently available)
      • Both mother and fetus stable
      • Absence of active bleeding or contractions
      • Patient lives close to the hospital

Ultrasound Evaluation

  • Perform ultrasound exam to evaluate placental location prior to digital vaginal exam
    • Placental previa: Use transvaginal ultrasound
    • Vasa previa: Pulsed-wave Doppler may help identify a fetal arterial vessel (with FH rate) or fetal vessels with venous flow
  • Placenta accreta: Ultrasound can be used, but sensitivity (89 to 92%) and specificity (92 to 97%) less than that of placenta previa and vasa previa
  • Placental abruption: Use clinical suspicion/judgement to determine management as ultrasound can miss this diagnosis in 20 to 50% of the cases
  • MRI in women who are actively bleeding is not recommended

Laboratory Evaluation

  • Depends on clinical status and may include
    • CBC and platelets
    • Type and cross
    • Coag studies: PT/PPT/INR/fibrinogen
    • If transfusion likely: BUN, Cr and lytes
  • Wall clot test
    • Place blood in plain (red top) tube
    • Normal expectation is clot within 6 min
  • Rh negative patient
    • Assess maternal-fetal hemorrhage
      • Quantitative rosette test
      • Qualitative Kleihauer-Betke stain
      • Flow cytometry
    • Administer standard Rh immunoglobulin dose of 300 μg
      • Increase as needed based on quantitative testing

Initial Stabilization for Delivery

  • 2 large-bore intravenous lines
  • Obtain results from lab testing above, especially blood type
    • O-neg blood may need to be identified and prepared in the interim
  • Crossmatch for an initial 2 to 4 U of blood
  • Utilize hemorrhage protocol in units where available
  • Fetal heart monitoring is indicated

Evidence Grading System

  • 1A: Strong recommendation | High-quality evidence
  • 1B: Strong recommendation | Moderate-quality evidence
  • 2C: Weak recommendation | Low-quality evidence

Learn More – Primary Sources:

Society for Maternal-Fetal Medicine (SMFM) Consult Series #44: management of bleeding in the late preterm period

ACOG SMFM Committee Opinion 831: Medically Indicated Late-Preterm and Early-Term Deliveries

Placenta Previa – Nomenclature, Diagnosis and Clinical Management

Clinical Actions:

The incidence of placenta previa is 1/200 pregnancies. Most cases of placenta previa will be identified prenatally by prenatal ultrasound. The following is recommended regarding mode and timing of delivery

  • Placenta previa: Cesarean delivery only
  • Placenta edge is ≥2.0 cm from the internal cervical os
    • Trial of labor is appropriate
  • Placental edge is between 1.0 cm and 2.0 cm from the internal cervical os
    • Management is uncertain
  • Timing of delivery in stable cases
    • ACOG/SMFM: 36w0d to 37w6d
  • Hospitalize when there are contractions or vaginal bleeding
  • Consider corticosteroids to enhance pulmonary maturity when there is vaginal bleeding <34 weeks gestation
  • The benefits of tocolysis, bed rest, pelvic rest and reduced activity is uncertain

Synopsis:

The nomenclature has been modified and the terms partial and marginal have been eliminated. All placentas which overlie or abut the internal cervical os (to any degree) should be referred to as placenta previa. A placenta which is near to but not overlying the os is termed a low-lying placenta.

Key points:

  • Role of ultrasound
    • Transvaginal ultrasound is the recommended approach
    • Transvaginal ultrasound is more accurate than transabdominal approach
    • If placenta previa is suspected on transabdominal ultrasound, a transvaginal ultrasound should be performed
  • Placenta previa identified during second trimester ultrasound
    • Placenta previa may be seen in 1 to 4% of second trimester ultrasound exams
    • 10 to 20% of previas diagnosed at 20 weeks gestation will remain a previa in the late 3rd trimester
    • Repeat ultrasound at 32 weeks gestation
  • The incidence of placenta previa is increased by
    • Number of previous cesarean sections
    • Number of previous spontaneous deliveries
    • the number of elective terminations
    • prior uterine surgery
    • maternal parity
    • maternal age
    • smoking
    • cocaine use
    • multiple gestations
    • prior placenta previa
  • Fetal complications are primarily those associated with prematurity
  • There is an increased risk of postpartum hemorrhage in patient with placenta previa
  • General anesthesia may increase blood loss without improving safety


Learn More – Primary Sources:

Abnormal Placentation: Placenta Previa, Vasa Previa, and Placenta Accreta

Society for Maternal-Fetal Medicine (SMFM) Consult Series #44: management of bleeding in the late preterm period

The Incidence of Postpartum Hemorrhage in Pregnant Women with Placenta Previa: A Systematic Review and Meta-Analysis

Analysis of first and second trimester maternal serum analytes for the prediction of morbidly adherent placenta requiring hysterectomy