Placenta Previa, Emergency Medicine

Basics

Description

Placental tissue overlying or proximate to the internal cervical os
Uterine enlargement and cervical dilation cause placental vessels near the cervix to tear, resulting in vaginal bleeding
>90% of placenta previa diagnosed before 20 weeks will migrate and have normal placental location at term
If placenta covers the internal os by >20 mm, then previa is expected at birth
Increased amount of placental overlap (>15 " ô23 mm) predicts placenta previa present at birth
Causes 20% of all antepartum hemorrhage
Classifications:
- Complete placenta previa: Cervical os is completely covered by placenta
- Partial placenta previa: Cervical os is partially covered by placenta
- Marginal placenta previa: Edge of placenta is at margin of cervical os
- Low-lying placenta: Placenta edge is within 2 cm to cervical os

Etiology

Unknown etiology
Incidence: 4/1,000 births = 0.4% of pregnancies at term
Maternal mortality: 0.03%
Perinatal morbidity and mortality: Triple, due to preterm delivery
Factors affecting location of implantation:
- Increased number of curettages from spontaneous or induced abortions
- Abnormal endometrial vascularization
- Delayed ovulation
Risk factors:
- Multiparity (5% grand multiparous patients vs. 0.2% nulliparous)
- Multiple gestation
- Prior C-section (up to 3 â Ś increase, increases with number or prior C-sections)
- Increased maternal age (0.7% age <19 yr, 1% age ≥35 yr)
- Previous placenta previa (4 " ô8% recurrence)
- Smoking (2 " ô4 times increase)
- Male fetus (14% increase)
- Assisted fertilization
- Residence at higher altitude
- Asian maternal race
- Unexplained elevated maternal serum alpha fetal protein (MSAFP)
Associated conditions:
- Congenital anomalies
- Abnormal fetal presentation
- Preterm premature rupture of the membranes
- Amniotic fluid embolism; associated with pathologies of the placenta
- Vasa previa: Fetal vessels course through membranes and cover os
- Placenta accreta, increta, percreta (growth of placenta into uterine wall) occur in 5 " ô10% of patients with placenta previa; sustained bleeding may require C-section hysterectomy

Diagnosis

Signs and Symptoms

Painless vaginal bleeding in pregnancy after 20 wk is placenta previa until proven otherwise é á
History

Painless bright red vaginal bleeding in 70%
Uterine contraction in 20%
Common incidental finding on US in 2nd trimester (6% at 16 " ô18 wk)
1st episode of bleeding typically occurs at 27 " ô32 wk
Bleeding may range from minor to massive; number of bleeding episodes does not correlate with degree of placenta previa
Inciting factors " öusually 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 patients 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 é á

Diagnosis Tests & Interpretation

Lab

CBC, platelets
Type and screen; upgrade to cross-match if transfusion is indicated
Kleihauer " ôBetke (KB) " ödetects >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 " ô98% 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 " Ł of labor

Treatment

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 " ô35%
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 " ô34 wk to stimulate prenatal lung maturity
Emergency C-section or delivery for continued bleeding or fetal compromise

Medication

RhoGAM: 1 vial (300 Ä ╝g) 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 " ô4 g/h; adjust to contractions
Betamethasone: 12 mg IM q24h â Ś 2 doses

Follow-Up

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 " ô20 mm: Repeat US at 28 wk
- Placenta >20 mm over os is unlikely to resolve. C-section at 36 " ô37 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

Followup Recommendations

Patients with incidental finding of placenta previa found at <20 wk will need outpatient US to determine migration of placenta é á

Pearls and Pitfalls

Do not perform digital vaginal exam if suspect vaginal bleeding after 2nd trimester. Do US first
Sterile speculum exam and transvaginal US are safe and do not increase bleeding
Painless vaginal bleeding after 20 wk is placenta previa until proven otherwise
Painful vaginal bleeding after 20 wk is placental abruption until proven otherwise
The 2 above conditions can occur simultaneously

Additional Reading

Cunningham é áFG, Leveno é áKJ, Bloom é áSL, et al. Williams ' Obstetrics. 23rd ed. New York, NY: McGraw-Hill; 2009.
DynaMed. Placenta previa. 2009. Available at http://www.DynamicMedical.com
Hacker é áNF, Gambone é áJC, Hobel é áCJ. Hacker and Moores Essentials of Obstetrics and Gynecology. 5th ed. Philadelphia, PA: WB Saunders; 2010.
Lockwood é áCJ, Russo-Stieglitz é áK. Clinical manifestations and diagnosis of Placenta Previa. UpToDate; Wolters Kluwer; 2012. Available at http://www.uptodate.com/patients/content/topic.do?topicKey= ó ł ╝18112/pmocgerp3
Marx é áJA, Hockberger é áRS, Walls é áRM, et al. Rosen's Emergency Medicine: Concepts and Clinical Practice. 7th ed. St. Louis, MO: Mosby; 2009.
Scott é áJR, Gibbs é áRS, Karlan é áBY, et al. Danforth's Obstetrics and Gynecology. 10th ed. Philadelphia, PA: Lippincot Williams & Wilkins; 2008.

Codes

ICD9

641.00 Placenta previa without hemorrhage, unspecified as to episode of care or not applicable
641.01 Placenta previa without hemorrhage, delivered, with or without mention of antepartum condition
641.10 Hemorrhage from placenta previa, unspecified as to episode of care or not applicable
641.11 Hemorrhage from placenta previa, delivered, with or without mention of antepartum condition
641.03 Placenta previa without hemorrhage, antepartum condition or complication
641.0 Placenta previa without hemorrhage
641.1 Hemorrhage from placenta previa

ICD10

O44.00 Placenta previa specified as w/o hemorrhage, unsp trimester
O44.03 Placenta previa specified as w/o hemorrhage, third trimester
O44.10 Placenta previa with hemorrhage, unspecified trimester
O44.13 Placenta previa with hemorrhage, third trimester
O44.01 Placenta previa specified as w/o hemorrhage, first trimester
O44.02 Placenta previa specified as w/o hemor, second trimester
O44.0 Placenta previa specified as without hemorrhage
O44.11 Placenta previa with hemorrhage, first trimester
O44.12 Placenta previa with hemorrhage, second trimester
O44.1 Placenta previa with hemorrhage
O44 Placenta previa

SNOMED

36813001 Placenta previa (disorder)
198903000 Placenta previa with hemorrhage
198899007 placenta previa without hemorrhage - delivered (disorder)
198905007 Placenta previa with hemorrhage - delivered
15663008 placenta previa centralis (disorder)
24095001 placenta previa partialis (disorder)
7792000 Placenta previa without hemorrhage

Home

Erectile Dysfunction

Doctor123.org