SIGNS AND SYMPTOMS 
Painlessvaginal bleeding in pregnancy after 20 wk is placenta previa until proven otherwise
History
- Painless bright red vaginal bleeding in 70%
- Uterine contraction in 20%
- Common incidental finding on US in 2nd trimester (6% at 16–18 wk)
- 1st episode of bleeding typically occurs at 27–32 wk
- Bleeding may range from minor to massive; number of bleeding episodes does not correlate with degree of placenta previa
- Inciting factors—usually no cause; recent intercourse or heavy exercise may contribute
- Initial bleeding is often self-limited and not lethal, but often recurs
Physical Exam
- Never do a digital exam or instrument probe of the cervix in 2nd-trimester vaginal bleeding until placenta previa is ruled out
- Sterile speculum exam can be safely performed prior to US to identify if blood is from the os, a vaginal lesion, or hemorrhoids
- Blood seen at patient's feet is a sign of heavy bleeding
- Hypotension and tachycardia may indicate hemorrhagic shock
- Fetal heart tones should be monitored along with other vital signs
ESSENTIAL WORKUP
Vaginal ultrasonography is the diagnostic procedure of choice
DIAGNOSIS TESTS & INTERPRETATION
Lab
- CBC, platelets
- Type and screen; upgrade to cross-match if transfusion is indicated
- Kleihauer–Betke (KB)—detects > 5 mL of fetal cells in maternal circulation (it takes only 0.1 mL to sensitize mother if Rh negative)
- If coagulopathy suspected (rare): Prothrombin time/partial thromboplastin time, fibrin-split products, fibrinogen (< 300 mg/dL is abnormal)
- Rh status
Imaging
- Transabdominal US: 93–98% accurate:
- False negative: Obesity, posterior or lateral placenta, fetal head over cervical os
- False positive: Overdistended bladder
- No sufficient accuracy for placenta previa position, need to obtain transvaginal US if placenta previa is detected or uncertain findings
- Transvaginal US: 100% accurate:
- Vaginal probe does not exacerbate bleeding
- Color flow Doppler US: Used to determine placenta accreta
- MRI: May be useful in evaluating placental abnormalities such as accreta and percreta
DIFFERENTIAL DIAGNOSIS
- Placenta abruption (may occur concurrently)
- Uterine rupture
- Fetal vessel rupture
- Cervical/vaginal trauma
- Cervical/vaginal lesions
- Bleeding disorder
- Spontaneous abortion
- "Bloody show" of labor
[Outline]
PRE-HOSPITAL
- Patient with vaginal bleeding at > 24 wk should be transported to a facility that can handle high risk and premature delivery
- Place patient in left lateral recumbent position if hypotensive in 2nd half of pregnancy
- O2 and IV as with other patients
INITIAL STABILIZATION/THERAPY
- Resuscitation for hemorrhagic shock as with any source with monitoring of fetus and higher cut off of blood transfusion
- ABCs
- 2 large-bore IVs with normal saline (NS) or lactated Ringer (LR) for resuscitation
- Left lateral recumbent position if hypotensive in 2nd half of pregnancy
- Fluid resuscitation
- Blood transfusion for hematocrit (Hct) < 30 or hypotension not responding to fluids
- Fresh-frozen plasma if coagulopathy
- Fetal monitoring (heart rate < 120 or > 160 bpm is abnormal)
- Immediate OB consultation for symptomatic patients
ED TREATMENT/PROCEDURES
- Emergent OB consultation for patients with active bleeding
- Volume resuscitation with 2 large-bore IVs with NS or LR
- Blood transfusion to keep Hct 30–35%
- RhoGAM if mother is Rh negative
- Fetal monitoring
- Keep NPO and on bed rest until considered stable by OB
- Magnesium sulfate only for contractions of preterm labor when delivery is not recommended
- Antenatal steroids (betamethasone) at 24–34 wk to stimulate prenatal lung maturity
- Emergency C-section or delivery for continued bleeding or fetal compromise
MEDICATION
- RhoGAM: 1 vial (300 µg) IM if not already given at 28 wk; may need > 1 vial if KB indicates > 15 mL of fetal RBS
- Magnesium sulfate: 6 g IV over 20 min, then 2–4 g/h; adjust to contractions
- Betamethasone: 12 mg IM q24h × 2 doses
[Outline]
DISPOSITION
Admission Criteria
- Active bleeding placental previa is a potential obstetric emergency, and all patients should be admitted
- Select patients may be managed on outpatient basis if bleeding is resolved. In consultation with OB
Discharge Criteria
- Asymptomatic patients
- Bed rest is not necessary. Avoid strenuous physical activity. Report bleeding or contractions
- < 20 wk and placenta not over the os: No special follow up necessary
- < 20 wk and placenta 0–20 mm: Repeat US at 28 wk
- Placenta > 20 mm over os is unlikely to resolve. C-section at 36–37 wk
- Pelvic rest (no intercourse or tampons in vagina) if placenta previa found after 28 wk or at any time if associated with bleeding
- 70% of patients will have a 2nd episode of bleeding
FOLLOW-UP RECOMMENDATIONS
Patients with incidental finding of placenta previa found at < 20 wk will need outpatient US to determine migration of placenta
[Outline]
- Cunningham FG, Leveno KJ, Bloom SL, et al. Williams' Obstetrics. 23rd ed. New York, NY: McGraw-Hill; 2009.
- DynaMed. Placenta previa. 2009. Available at http://www.DynamicMedical.com
- Hacker NF, Gambone JC, Hobel CJ. Hacker and Moore's Essentials of Obstetrics and Gynecology. 5th ed. Philadelphia, PA: WB Saunders; 2010.
- Lockwood CJ, Russo-Stieglitz K. Clinical manifestations and diagnosis of Placenta Previa. UpToDate; Wolters Kluwer; 2012. Available at http://www.uptodate.com/patients/content/topic.do?topicKey=~18112/pmocgerp3
- Marx JA, Hockberger RS, Walls RM, et al. Rosen's Emergency Medicine: Concepts and Clinical Practice. 7th ed. St. Louis, MO: Mosby; 2009.
- Scott JR, Gibbs RS, Karlan BY, et al. Danforth's Obstetrics and Gynecology. 10th ed. Philadelphia, PA: Lippincot Williams & Wilkins; 2008.
See Also (Topic, Algorithm, Electronic Media Element)
Placental Abruption