I. Definition: obstruction of or proximity to internal cervical os by the placenta

  1. Vasa Previa = placental vessel lying across cervical os, e.g. from main placenta to succenturiate lobe; if bleeding, the hemorrhage is of FETAL blood

II. Clinical presentation: 

  1. Classically, painless bleeding in the 3rd trimester (most commonly at 29-30 weeks gestation)
  2. Pain from labor may be present
  3. May occur in the 2nd trimester as well
  4. Often first bleed is after intercourse

III. Risk factors:

  1. Prior endometrial or myometrial trauma
  2. Multiparity
  3. Advanced maternal age
  4. Prior cesarian section (RR 1.5 for 2nd birth if first was by cesarian; RR 2.0 for 3rd birth if first two were by cesarian) (Obs. Gyn. 107:771, 2006--JW)
  5. Prior induced abortion or D & C
  6. Multiple gestation

IV. Diagnosis: ultrasound (has 7% false-negative rate as of 1980)

V. Sequelae: associated with small for gest. age infants; increased risk of subsequent cerebral palsy

VI. Management:

  1. Avoid digital pelvic examination; gentle speculum exam OK
  2. If bleeding is severe, immediate c/s
  3. Labs: CBC, PT/PTT, Type & Cross; transfuse as needed
  4. Electronic fetal monitoring
  5. Tocolytics if with uterine contractions (can be stimulated by bleeding); Mg is "agent of choice" (ACOG rvw).
  6. If remote from term:
    1. If stable, consider amniocentesis for fetal maturity
    2. RhoGAM if Rh-negative
    3. Pelvic rest
    4. Expectant management
  7. Deliver by c/s unless low-lying or marginal previa (in which case vaginal delivery with close backup and c/s availability is acceptable).
  8. Anticipate placenta accreta which often comes along with previa
  9. Risk stratification in pts with placenta previa
    1. In a prospective study in 68 pts with placenta previa, short cervical length (3cm or less) on transvaginal ultrasound at 32wks was associated with sig. greater incidence of hospitalization for bleeding (75% vs. 28%) and preterm delivery (RR about 3) (Obs. Gynecol. 116:595, 2010-JW)

(Source: Clin. Obs. Gyn 33:414, 1990; 2002 Advanced Life Support in Obstetrics course syllabus; American Academy of Family Physicians)