AUTHOR AND EDITOR INFORMATION

Section 1 of 10  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• References

INTRODUCTION

Section 2 of 10  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• References

Background

Placenta previa is an obstetric complication that occurs in the second and third trimesters of pregnancy. It may cause serious morbidity and mortality to both the fetus and the mother. It is one of the leading causes of vaginal bleeding in the second and third trimesters.

Placenta previa is generally defined as the implantation of the placenta over or near the internal os of the cervix.

• Total placenta previa occurs when the internal cervical os is completely covered by the placenta.
• Partial placenta previa occurs when the internal os is partially covered by the placenta.
• Marginal placenta previa occurs when the placenta is at the margin of the internal os.
• Low-lying placenta previa occurs when the placenta is implanted in the lower uterine segment. In this variation, the edge of the placenta is near the internal os but does not reach it.

Pathophysiology

The exact etiology of placenta previa is unknown. The condition may be multifactorial and is postulated to be related to multiparity, multiple gestations, advanced maternal age, previous cesarean delivery, previous abortion, and possibly, smoking.

Unlike first trimester bleeding, second and third trimester bleeding is usually secondary to abnormal placental implantation.

Frequency

United States

Placenta previa complicates approximately 5 of 1,000 deliveries and has a mortality rate of 0.03%. Recent data recorded from 1989-1997 indicated placenta previa occurs in 2.8 per 1000 live births in the United States.

Mortality/Morbidity

• The maternal mortality rate secondary to placenta previa is approximately 0.03%. Babies born to women with placenta previa tend to weigh less than babies born to women without placenta previa. The risk of neonatal mortality is higher for placenta previa babies versus pregnancies without placenta previa.
• The great majority of deaths are related to uterine bleeding and the complication of disseminated intravascular coagulopathy.
• In early pregnancy, a partial previa can often self-correct as the uterus enlarges and the placental site moves cephalad.

Race

Significance of race is somewhat controversial. Some studies suggest an increased risk of placenta previa among African Americans and Asians, while other studies cite no difference.

Age

Women older than 30 years are 3 times more likely to have placenta previa than women younger than 20 years.

CLINICAL

Section 3 of 10  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• References

History

• Vaginal bleeding
• • It is apt to occur suddenly during the third trimester.
  • Bleeding is usually bright red and painless. Some degree of uterine irritability is present in about 20% of the cases.
  • Initial bleeding is not usually profuse enough to cause death; it spontaneously ceases, only to recur later.
  • The first bleed occurs (on average) at 27-32 weeks' gestation.
  • Contractions may or may not occur simultaneously with the bleeding.

Physical

• Profuse hemorrhage
• Hypotension
• Tachycardia
• Soft and nontender uterus
• Normal fetal heart tones (usually)
• Vaginal and rectal examinations
• • Do not perform these examinations in the ED because they may provoke uncontrollable bleeding.
  • Perform examinations in the operating room under double set-up conditions (ie, ready for emergent cesarean delivery).

Causes

• Prior uterine insult or injury
• Risk factors
• • Prior placenta previa (4-8%)
  • First subsequent pregnancy following a cesarean delivery
  • Multiparity (5% in grand multiparous patients)
  • Advanced maternal age
  • Multiple gestations
  • Prior induced abortion
  • Smoking

DIFFERENTIALS

Section 4 of 10  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• References

Other Problems to be Considered

Vasa previa
Infection
Vaginal bleeding
Lower genital tract lesions
Bloody show

WORKUP

Section 5 of 10  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• References

Lab Studies

• Beta-human chorionic gonadotropin (beta-hCG) subunit
• Rh compatibility
• Fibrin split products (FSP) and fibrinogen levels
• Prothrombin time (PT)/activated partial thromboplastin time (aPTT)
• Type and hold for at least 4 units
• Complete blood count (CBC)
• Apt test to determine fetal origin of blood (as in the case of vasa previa)
• Wright stain applied to a slide smear of vaginal blood, looking for nucleated red blood cells (RBCs), not adult blood
• Lecithin/sphingomyelin (L/S) ratio for fetal maturity, if needed

Imaging Studies

• Transabdominal ultrasonography
• • A simple, precise, and safe method to visualize the placenta, this ultrasonography has an accuracy of 93-98%.
  • False-positive results can occur secondary to focal uterine contractions or bladder distention.
• Transvaginal ultrasonography
• • Recent studies have shown that the transvaginal method is safer and more accurate than the transabdominal method. Transvaginal ultrasonography is also considered more accurate than transabdominal ultrasonography. In one study, 26% of placental localization diagnosed by transabdominal ultrasonography was later changed using transvaginal ultrasonography.
  • The angle between the transvaginal probe and the cervical canal is such that the probe does not enter the cervical canal. Some advocate insertion of the probe no more than 3 cm for visualization of the placenta.
• Transperineal ultrasonography: Transperineal ultrasonography has been suggested as an alternate method, especially when instrumentation of the vaginal canal with a probe is a concern. A recent study suggests that transperineal ultrasonography may compliment transabdominal ultrasonography and help eliminate false-positive results using the transabdominal method alone.
• Magnetic resonance imaging (MRI): MRI has been suggested as a safe and alternate method and may be useful in determining the presence of placenta accreta. A large trial determining the efficacy and safety of the use of MRI during pregnancy has not been performed, and further investigation is required.

Other Tests

• Kleihauer-Betke test, if concerned about fetal-maternal transfusion
• Bedside clot test

Procedures

• If the location of the placenta is unknown and sonography is not available, a double set-up bimanual examination under anesthesia (EUA) may be performed in the operating room.

TREATMENT

Section 6 of 10  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• References

Prehospital Care

The key to prehospital care is to ensure hemodynamic stability of the patient and transfer to an appropriate facility.

Emergency Department Care

• Because of the potential morbidity and mortality secondary to profuse bleeding, obtain immediate gynecologic consultation, if available. Before gynecologic consultation or transfer, the hemodynamic stability of the patient should be addressed. This includes the establishment of 2 large-bore intravenous access lines with intravenous crystalloids or blood products, as necessary.
• Obtain continuous fetal monitoring, if available.
• If the fetus is preterm and immediate delivery is unnecessary (eg, fetus <37 weeks' gestation and hemorrhage not present), the patient may be treated expectantly on an outpatient basis.
• If the fetus is reasonably mature (ie, >37 weeks' gestation) and the patient is in labor or if severe hemorrhage is present, therapy is directed at the delivery of the fetus. The patient should receive crystalloids and/or blood, and the patient should be transferred to the operating room with double set-up conditions.
• A trial of labor may be considered for anterior marginal previa, including oxytocin (Pitocin) augmentation.

Consultations

Consult an obstetrician.

MEDICATION

Section 7 of 10  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• References

The ED goal should be directed at the hemodynamic stability of the patient. The primary therapeutic agents should be intravenous crystalloids and/or transfusions.

Recent studies are now using prothrombin complex and recombinant factor VII to control hemorrhage associated with obstetric complications and placenta previa.

Drug Category: Corticosteroids

Steroids may be administered after consultation with a gynecologist, if vaginal bleeding is mild and intermittent, if the patient is not in labor, and if gestation is less than 37 weeks.

Drug Category: Tocolytics

Some specialists advocate tocolytics to promote the time for expectant management of symptomatic placenta previa. They should only be used after consultation with an obstetrician. A recent study seems to suggest that the use of tocolytics increases the duration of pregnancy and increases the baby's birth weight without causing adverse effects on the mother and the fetus.

FOLLOW-UP

Section 8 of 10  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• References

Further Inpatient Care

• Bed rest in the hospital may be recommended for some women with bleeding. A select population of women may be eligible for outpatient management.

Deterrence/Prevention

• Patients with placenta previa should decrease activity to avoid rebleeding.
• Pelvic examinations and intercourse should be avoided.
• Some women will bleed and possibly go into labor without any inciting cause.

Complications

• Maternal mortality (rare)
• Rebleeding
• Intrauterine growth retardation (IUGR)
• Congenital anomalies
• Fetal anemia and Rh isoimmunization

Prognosis

• Patients with complete placenta previa tend to have poorer pregnancy outcomes. They tend to deliver more prematurely and may require hysterectomies at the time of delivery.

Patient Education

• For excellent patient education resources, visit eMedicine's Pregnancy and Reproduction Center and Women's Health Center. Also, see eMedicine's patient education articles Pregnancy, Bleeding and Vaginal Bleeding.

MISCELLANEOUS

Section 9 of 10  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• References

Medical/Legal Pitfalls

• Instruments or fingers should not be placed near the cervix during a vaginal examination because uncontrolled bleeding can result. Do not perform vaginal or rectal examinations in the ED.

REFERENCES

Section 10 of 10

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• References

• Ananth CV, Smulian JC, Vintzileos AM. The effect of placenta previa on neonatal mortality: a population-based study in the United States, 1989 through 1997. Am J Obstet Gynecol. May 2003;188(5):1299-304. [Medline].
• Besinger RE, Moniak CW, Paskiewicz LS, Fisher SG, Tomich PG. The effect of tocolytic use in the management of symptomatic placenta previa. Am J Obstet Gynecol. Jun 1995;172(6):1770-5; discussion 1775-8. [Medline].
• Crane S, Chun B, Acker D. Treatment of obstetrical hemorrhagic emergencies. Curr Opin Obstet Gynecol. Oct 1993;5(5):675-82. [Medline].
• Dola CP, Garite TJ, Dowling DD, Friend D, Ahdoot D, Asrat T. Placenta previa: does its type affect pregnancy outcome?. Am J Perinatol. Oct 2003;20(7):353-60. [Medline].
• Gidiri M, Noble W, Rafique Z, Patil K, Lindow SW. Caesarean section for placenta praevia complicated by postpartum haemorrhage managed successfully with recombinant activated human coagulation Factor VIIa. J Obstet Gynaecol. Nov 2004;24(8):925-6. [Medline].
• Glynn JC, Plaat F. Prothrombin complex for massive obstetric haemorrhage. Anaesthesia. Feb 2007;62(2):202-3. [Medline].
• Iyasu S, Saftlas AK, Rowley DL, Koonin LM, Lawson HW, Atrash HK. The epidemiology of placenta previa in the United States, 1979 through 1987. Am J Obstet Gynecol. May 1993;168(5):1424-9. [Medline].
• Otsubo Y, Shinagawa T, Chihara H, Araki T. Conservative management of a case of placenta praevia percreta. Aust N Z J Obstet Gynaecol. Nov 1999;39(4):518-9. [Medline].
• Rani PR, Haritha PH, Gowri R. Comparative study of transperineal and transabdominal sonography in the diagnosis of placenta previa. J Obstet Gynaecol Res. Apr 2007;33(2):134-7. [Medline].
• Rathore SS, McMahon MJ. Racial variation in the frequency of intrapartum hemorrhage. Obstet Gynecol. Feb 2001;97(2):178-83. [Medline].
• Sharma A, Suri V, Gupta I. Tocolytic therapy in conservative management of symptomatic placenta previa. Int J Gynaecol Obstet. Feb 2004;84(2):109-13. [Medline].
• Smith RS, Lauria MR, Comstock CH, Treadwell MC, Kirk JS, Lee W, et al. Transvaginal ultrasonography for all placentas that appear to be low-lying or over the internal cervical os. Ultrasound Obstet Gynecol. Jan 1997;9(1):22-4. [Medline].
• Taber. Manual of Gynecologic and Obstetric Emergencies. 2^nd ed. Philadelphia, Pa: WB Saunders Co; 1984:313-318.
• Taylor VM, Peacock S, Kramer MD, Vaughan TL. Increased risk of placenta previa among women of Asian origin. Obstet Gynecol. Nov 1995;86(5):805-8. [Medline].
• Timor-Tritsch IE, Monteagudo A. Diagnosis of placenta previa by transvaginal sonography. Ann Med. Jun 1993;25(3):279-83. [Medline].
• Williams, Cunningham, Macdonald. Williams' Obstetrics. 19^th ed. Norwalk, Conn: Appleton & Lange; 1993:836-841.
• Zhang J, Savitz DA. Maternal age and placenta previa: a population-based, case-control study. Am J Obstet Gynecol. Feb 1993;168(2):641-5. [Medline].

Article Last Updated: Aug 23, 2007