eMedicine Specialties > Emergency Medicine > Obstetrics & Gynecology

Placenta Previa

Author: Patrick Ko, MD, Clinical Assistant Professor, Department of Emergency Medicine, New York University Medical School; Assistant Program Director, Department of Emergency Medicine, North Shore University Hospital
Coauthor(s): Young Yoon, MD, Associate Director, Assistant Professor, Department of Emergency Medicine, Mount Sinai Medical Center
Contributor Information and Disclosures

Updated: Aug 23, 2007

Introduction

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

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

More on Placenta Previa

Overview: Placenta Previa
Differential Diagnoses & Workup: Placenta Previa
Treatment & Medication: Placenta Previa
Follow-up: Placenta Previa
References
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References

  1. 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].

  2. 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].

  3. Crane S, Chun B, Acker D. Treatment of obstetrical hemorrhagic emergencies. Curr Opin Obstet Gynecol. Oct 1993;5(5):675-82. [Medline].

  4. 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].

  5. 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].

  6. Glynn JC, Plaat F. Prothrombin complex for massive obstetric haemorrhage. Anaesthesia. Feb 2007;62(2):202-3. [Medline].

  7. 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].

  8. 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].

  9. 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].

  10. Rathore SS, McMahon MJ. Racial variation in the frequency of intrapartum hemorrhage. Obstet Gynecol. Feb 2001;97(2):178-83. [Medline].

  11. 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].

  12. 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].

  13. Taber. Manual of Gynecologic and Obstetric Emergencies. 2nd ed. Philadelphia, Pa: WB Saunders Co; 1984:313-318.

  14. 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].

  15. Timor-Tritsch IE, Monteagudo A. Diagnosis of placenta previa by transvaginal sonography. Ann Med. Jun 1993;25(3):279-83. [Medline].

  16. Williams, Cunningham, Macdonald. Williams' Obstetrics. 19th ed. Norwalk, Conn: Appleton & Lange; 1993:836-841.

  17. 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].

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Further Reading

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Keywords

disseminated intravascular coagulopathy, placenta previa, vaginal bleeding, pregnancy complications, obstetric complications, total placenta previa, partial placenta previa, marginal placenta previa, low-lying placenta previa, internal cervical os, abnormal placental implantation, uterine bleeding

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Contributor Information and Disclosures

Author

Patrick Ko, MD, Clinical Assistant Professor, Department of Emergency Medicine, New York University Medical School; Assistant Program Director, Department of Emergency Medicine, North Shore University Hospital
Patrick Ko, MD is a member of the following medical societies: American College of Emergency Physicians and Society for Academic Emergency Medicine
Disclosure: Nothing to disclose.

Coauthor(s)

Young Yoon, MD, Associate Director, Assistant Professor, Department of Emergency Medicine, Mount Sinai Medical Center
Young Yoon, MD is a member of the following medical societies: Society for Academic Emergency Medicine
Disclosure: Nothing to disclose.

Medical Editor

Joseph J Sachter, MD, FACEP, Consulting Staff, Department of Emergency Medicine, Muhlenberg Regional Medical Center
Joseph J Sachter, MD, FACEP is a member of the following medical societies: American Academy of Emergency Medicine, American College of Emergency Physicians, American College of Physician Executives, American Medical Association, and Society for Academic Emergency Medicine
Disclosure: Nothing to disclose.

Pharmacy Editor

Francisco Talavera, PharmD, PhD, Senior Pharmacy Editor, eMedicine
Disclosure: Nothing to disclose.

Managing Editor

Mark Zwanger, MD, MBA, Assistant Professor, Department of Emergency Medicine, Thomas Jefferson University
Mark Zwanger, MD, MBA is a member of the following medical societies: American Academy of Emergency Medicine, American College of Emergency Physicians, and American Medical Association
Disclosure: Nothing to disclose.

CME Editor

John Halamka, MD, Chief Information Officer, CareGroup Healthcare System, Assistant Professor of Medicine, Department of Emergency Medicine, Beth Israel Deaconess Medical Center; Assistant Professor of Medicine, Harvard Medical School
John Halamka, MD is a member of the following medical societies: American Academy of Emergency Medicine and Society for Academic Emergency Medicine
Disclosure: Nothing to disclose.

Chief Editor

Pamela L Dyne, MD, Associate Professor, Program Director, Department of Medicine, Division of Emergency Medicine, University of California at Los Angeles School of Medicine
Pamela L Dyne, MD is a member of the following medical societies: American College of Emergency Physicians, American Institute of Ultrasound in Medicine, and Society for Academic Emergency Medicine
Disclosure: Nothing to disclose.

 
 
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