PLACENTA PREVIA

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

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