Official reprint from UpToDate®
www.uptodate.com ©2017 UpToDate, Inc. and/or its affiliates. All Rights Reserved.

Placenta previa: Epidemiology, clinical features, diagnosis, morbidity and mortality

Charles J Lockwood, MD, MHCM
Karen Russo-Stieglitz, MD
Section Editors
Deborah Levine, MD
Vincenzo Berghella, MD
Deputy Editor
Vanessa A Barss, MD, FACOG


Placenta previa refers to the presence of placental tissue that extends over the internal cervical os. Sequelae include the potential for severe bleeding and preterm birth, as well as the need for cesarean delivery.

Placenta previa should be suspected in any pregnant woman beyond 20 weeks of gestation who presents with vaginal bleeding. For women who have not had a second-trimester ultrasound examination, bleeding after 20 weeks of gestation should prompt sonographic determination of placental location before digital vaginal examination is performed because palpation of the placenta can cause severe hemorrhage.

This topic will discuss the epidemiology, clinical features, diagnosis, morbidity, and mortality of placenta previa. The natural history of placenta, risk of bleeding, and management are reviewed separately. (See "Placenta previa: Management".)


Prevalence — In systematic reviews, the pooled prevalence of placenta previa is about 4 per 1000 births, but varies worldwide [1,2]. The prevalence is several-fold higher around 20 weeks of gestation (as high as 2 percent), but most previas identified early in pregnancy resolve before delivery. (See 'Natural history' below.)

Risk factors — Major risk factors for placenta previa include [3-15]:

To continue reading this article, you must log in with your personal, hospital, or group practice subscription. For more information on subscription options, click below on the option that best describes you:

Subscribers log in here

Literature review current through: Nov 2017. | This topic last updated: Aug 04, 2017.
The content on the UpToDate website is not intended nor recommended as a substitute for medical advice, diagnosis, or treatment. Always seek the advice of your own physician or other qualified health care professional regarding any medical questions or conditions. The use of this website is governed by the UpToDate Terms of Use ©2017 UpToDate, Inc.
  1. Faiz AS, Ananth CV. Etiology and risk factors for placenta previa: an overview and meta-analysis of observational studies. J Matern Fetal Neonatal Med 2003; 13:175.
  2. Cresswell JA, Ronsmans C, Calvert C, Filippi V. Prevalence of placenta praevia by world region: a systematic review and meta-analysis. Trop Med Int Health 2013; 18:712.
  3. Ananth CV, Smulian JC, Vintzileos AM. The association of placenta previa with history of cesarean delivery and abortion: a metaanalysis. Am J Obstet Gynecol 1997; 177:1071.
  4. National Institutes of Health Consensus Development Conference Statement. NIH Consensus Development Conference: Vaginal Birth After Cesarean: New Insights. March 8–10, 2010.
  5. Ananth CV, Demissie K, Smulian JC, Vintzileos AM. Placenta previa in singleton and twin births in the United States, 1989 through 1998: a comparison of risk factor profiles and associated conditions. Am J Obstet Gynecol 2003; 188:275.
  6. Demissie K, Breckenridge MB, Joseph L, Rhoads GG. Placenta previa: preponderance of male sex at birth. Am J Epidemiol 1999; 149:824.
  7. Yang Q, Wu Wen S, Caughey S, et al. Placenta previa: its relationship with race and the country of origin among Asian women. Acta Obstet Gynecol Scand 2008; 87:612.
  8. Rosenberg T, Pariente G, Sergienko R, et al. Critical analysis of risk factors and outcome of placenta previa. Arch Gynecol Obstet 2011; 284:47.
  9. Iyasu S, Saftlas AK, Rowley DL, et al. The epidemiology of placenta previa in the United States, 1979 through 1987. Am J Obstet Gynecol 1993; 168:1424.
  10. Macones GA, Sehdev HM, Parry S, et al. The association between maternal cocaine use and placenta previa. Am J Obstet Gynecol 1997; 177:1097.
  11. Rasmussen S, Albrechtsen S, Dalaker K. Obstetric history and the risk of placenta previa. Acta Obstet Gynecol Scand 2000; 79:502.
  12. Gurol-Urganci I, Cromwell DA, Edozien LC, et al. Risk of placenta previa in second birth after first birth cesarean section: a population-based study and meta-analysis. BMC Pregnancy Childbirth 2011; 11:95.
  13. Downes KL, Hinkle SN, Sjaarda LA, et al. Previous prelabor or intrapartum cesarean delivery and risk of placenta previa. Am J Obstet Gynecol 2015; 212:669.e1.
  14. Karami M, Jenabi E, Fereidooni B. The association of placenta previa and assisted reproductive techniques: a meta-analysis. J Matern Fetal Neonatal Med 2017; :1.
  15. Shobeiri F, Jenabi E. Smoking and placenta previa: a meta-analysis. J Matern Fetal Neonatal Med 2017; 30:2985.
  16. Lavery JP. Placenta previa. Clin Obstet Gynecol 1990; 33:414.
  17. Klar M, Michels KB. Cesarean section and placental disorders in subsequent pregnancies--a meta-analysis. J Perinat Med 2014; 42:571.
  18. Clark SL, Koonings PP, Phelan JP. Placenta previa/accreta and prior cesarean section. Obstet Gynecol 1985; 66:89.
  19. Getahun D, Oyelese Y, Salihu HM, Ananth CV. Previous cesarean delivery and risks of placenta previa and placental abruption. Obstet Gynecol 2006; 107:771.
  20. Gilliam M, Rosenberg D, Davis F. The likelihood of placenta previa with greater number of cesarean deliveries and higher parity. Obstet Gynecol 2002; 99:976.
  21. Weis MA, Harper LM, Roehl KA, et al. Natural history of placenta previa in twins. Obstet Gynecol 2012; 120:753.
  22. Rose GL, Chapman MG. Aetiological factors in placenta praevia--a case controlled study. Br J Obstet Gynaecol 1986; 93:586.
  23. Oyelese Y, Smulian JC. Placenta previa, placenta accreta, and vasa previa. Obstet Gynecol 2006; 107:927.
  24. Dashe JS, McIntire DD, Ramus RM, et al. Persistence of placenta previa according to gestational age at ultrasound detection. Obstet Gynecol 2002; 99:692.
  25. Mouer JR. Placenta previa: antepartum conservative management, inpatient versus outpatient. Am J Obstet Gynecol 1994; 170:1683.
  26. Becker RH, Vonk R, Mende BC, et al. The relevance of placental location at 20-23 gestational weeks for prediction of placenta previa at delivery: evaluation of 8650 cases. Ultrasound Obstet Gynecol 2001; 17:496.
  27. Taipale P, Hiilesmaa V, Ylöstalo P. Transvaginal ultrasonography at 18-23 weeks in predicting placenta previa at delivery. Ultrasound Obstet Gynecol 1998; 12:422.
  28. Rosati P, Guariglia L. Clinical significance of placenta previa detected at early routine transvaginal scan. J Ultrasound Med 2000; 19:581.
  29. Oppenheimer L, Holmes P, Simpson N, Dabrowski A. Diagnosis of low-lying placenta: can migration in the third trimester predict outcome? Ultrasound Obstet Gynecol 2001; 18:100.
  30. Cho JY, Lee YH, Moon MH, Lee JH. Difference in migration of placenta according to the location and type of placenta previa. J Clin Ultrasound 2008; 36:79.
  31. Fan D, Wu S, Liu L, et al. Prevalence of antepartum hemorrhage in women with placenta previa: a systematic review and meta-analysis. Sci Rep 2017; 7:40320.
  32. Cotton DB, Read JA, Paul RH, Quilligan EJ. The conservative aggressive management of placenta previa. Am J Obstet Gynecol 1980; 137:687.
  33. Silver R, Depp R, Sabbagha RE, et al. Placenta previa: aggressive expectant management. Am J Obstet Gynecol 1984; 150:15.
  34. McShane PM, Heyl PS, Epstein MF. Maternal and perinatal morbidity resulting from placenta previa. Obstet Gynecol 1985; 65:176.
  35. Crane JM, van den Hof MC, Dodds L, et al. Neonatal outcomes with placenta previa. Obstet Gynecol 1999; 93:541.
  36. Ruiter L, Eschbach SJ, Burgers M, et al. Predictors for Emergency Cesarean Delivery in Women with Placenta Previa. Am J Perinatol 2016; 33:1407.
  37. Reddy UM, Abuhamad AZ, Levine D, et al. Fetal imaging: executive summary of a joint Eunice Kennedy Shriver National Institute of Child Health and Human Development, Society for Maternal-Fetal Medicine, American Institute of Ultrasound in Medicine, American College of Obstetricians and Gynecologists, American College of Radiology, Society for Pediatric Radiology, and Society of Radiologists in Ultrasound Fetal Imaging workshop. Obstet Gynecol 2014; 123:1070.
  38. Thurmond A, Mendelson E, Böhm-Vélez M, et al. Role of imaging in second and third trimester bleeding. American College of Radiology. ACR Appropriateness Criteria. Radiology 2000; 215 Suppl:895.
  39. McClure N, Dornal JC. Early identification of placenta praevia. Br J Obstet Gynaecol 1990; 97:959.
  40. Oppenheimer L, Society of Obstetricians and Gynaecologists of Canada. Diagnosis and management of placenta previa. J Obstet Gynaecol Can 2007; 29:261.
  41. Quant HS, Friedman AM, Wang E, et al. Transabdominal ultrasonography as a screening test for second-trimester placenta previa. Obstet Gynecol 2014; 123:628.
  42. Timor-Tritsch IE, Yunis RA. Confirming the safety of transvaginal sonography in patients suspected of placenta previa. Obstet Gynecol 1993; 81:742.
  43. Sunna E, Ziadeh S. Transvaginal and transabdominal ultrasound for the diagnosis of placenta praevia. J Obstet Gynaecol 1999; 19:152.
  44. Smith RS, Lauria MR, Comstock CH, et al. Transvaginal ultrasonography for all placentas that appear to be low-lying or over the internal cervical os. Ultrasound Obstet Gynecol 1997; 9:22.
  45. Sherman SJ, Carlson DE, Platt LD, Medearis AL. Transvaginal ultrasound: does it help in the diagnosis of placenta previa? Ultrasound Obstet Gynecol 1992; 2:256.
  46. Leerentveld RA, Gilberts EC, Arnold MJ, Wladimiroff JW. Accuracy and safety of transvaginal sonographic placental localization. Obstet Gynecol 1990; 76:759.
  47. Tuzovic L. Complete versus incomplete placenta previa and obstetric outcome. Int J Gynaecol Obstet 2006; 93:110.
  48. Oya A, Nakai A, Miyake H, et al. Risk factors for peripartum blood transfusion in women with placenta previa: a retrospective analysis. J Nippon Med Sch 2008; 75:146.
  49. Dola CP, Garite TJ, Dowling DD, et al. Placenta previa: does its type affect pregnancy outcome? Am J Perinatol 2003; 20:353.
  50. Bahar A, Abusham A, Eskandar M, et al. Risk factors and pregnancy outcome in different types of placenta previa. J Obstet Gynaecol Can 2009; 31:126.
  51. Ghourab S. Third-trimester transvaginal ultrasonography in placenta previa: does the shape of the lower placental edge predict clinical outcome? Ultrasound Obstet Gynecol 2001; 18:103.
  52. Zaitoun MM, El Behery MM, Abd El Hameed AA, Soliman BS. Does cervical length and the lower placental edge thickness measurement correlates with clinical outcome in cases of complete placenta previa? Arch Gynecol Obstet 2011; 284:867.
  53. Saitoh M, Ishihara K, Sekiya T, Araki T. Anticipation of uterine bleeding in placenta previa based on vaginal sonographic evaluation. Gynecol Obstet Invest 2002; 54:37.
  54. Ghi T, Contro E, Martina T, et al. Cervical length and risk of antepartum bleeding in women with complete placenta previa. Ultrasound Obstet Gynecol 2009; 33:209.
  55. Stafford IA, Dashe JS, Shivvers SA, et al. Ultrasonographic cervical length and risk of hemorrhage in pregnancies with placenta previa. Obstet Gynecol 2010; 116:595.
  56. Sekiguchi A, Nakai A, Okuda N, et al. Consecutive cervical length measurements as a predictor of preterm cesarean section in complete placenta previa. J Clin Ultrasound 2015; 43:17.
  57. Shin JE, Shin JC, Lee Y, Kim SJ. Serial Change in Cervical Length for the Prediction of Emergency Cesarean Section in Placenta Previa. PLoS One 2016; 11:e0149036.
  58. Dawson WB, Dumas MD, Romano WM, et al. Translabial ultrasonography and placenta previa: does measurement of the os-placenta distance predict outcome? J Ultrasound Med 1996; 15:441.
  59. Simon EG, Fouche CJ, Perrotin F. Three-dimensional transvaginal sonography in third-trimester evaluation of placenta previa. Ultrasound Obstet Gynecol 2013; 41:465.
  60. Warshak CR, Eskander R, Hull AD, et al. Accuracy of ultrasonography and magnetic resonance imaging in the diagnosis of placenta accreta. Obstet Gynecol 2006; 108:573.
  61. Silver RM, Landon MB, Rouse DJ, et al. Maternal morbidity associated with multiple repeat cesarean deliveries. Obstet Gynecol 2006; 107:1226.
  62. Grobman WA, Gersnoviez R, Landon MB, et al. Pregnancy outcomes for women with placenta previa in relation to the number of prior cesarean deliveries. Obstet Gynecol 2007; 110:1249.
  63. Sheiner E, Shoham-Vardi I, Hallak M, et al. Placenta previa: obstetric risk factors and pregnancy outcome. J Matern Fetal Med 2001; 10:414.
  64. Gemer O, Segal S. Incidence and contribution of predisposing factors to transverse lie presentation. Int J Gynaecol Obstet 1994; 44:219.
  65. Olive EC, Roberts CL, Algert CS, Morris JM. Placenta praevia: maternal morbidity and place of birth. Aust N Z J Obstet Gynaecol 2005; 45:499.
  66. Brenner WE, Edelman DA, Hendricks CH. Characteristics of patients with placenta previa and results of "expectant management". Am J Obstet Gynecol 1978; 132:180.
  67. Varma TR. Fetal growth and placental function in patients with placenta praevia. J Obstet Gynaecol Br Commonw 1973; 80:311.
  68. Newton ER, Barss V, Cetrulo CL. The epidemiology and clinical history of asymptomatic midtrimester placenta previa. Am J Obstet Gynecol 1984; 148:743.
  69. Ananth CV, Demissie K, Smulian JC, Vintzileos AM. Relationship among placenta previa, fetal growth restriction, and preterm delivery: a population-based study. Obstet Gynecol 2001; 98:299.
  70. Räisänen S, Kancherla V, Kramer MR, et al. Placenta previa and the risk of delivering a small-for-gestational-age newborn. Obstet Gynecol 2014; 124:285.
  71. Weiner E, Miremberg H, Grinstein E, et al. The effect of placenta previa on fetal growth and pregnancy outcome, in correlation with placental pathology. J Perinatol 2016; 36:1073.
  72. Comeau J, Shaw L, Marcell CC, Lavery JP. Early placenta previa and delivery outcome. Obstet Gynecol 1983; 61:577.
  73. Harper LM, Odibo AO, Macones GA, et al. Effect of placenta previa on fetal growth. Am J Obstet Gynecol 2010; 203:330.e1.
  74. Nørgaard LN, Pinborg A, Lidegaard Ø, Bergholt T. A Danish national cohort study on neonatal outcome in singleton pregnancies with placenta previa. Acta Obstet Gynecol Scand 2012; 91:546.
  75. Kancherla V, Räisänen S, Gissler M, et al. Placenta previa and risk of major congenital malformations among singleton births in Finland. Birth Defects Res A Clin Mol Teratol 2015; 103:527.
  76. Kancherla V, Räisänen S, Gissler M, et al. Placenta previa and risk of major congenital malformations among singleton births in Finland. Birth Defects Res A Clin Mol Teratol 2015; 193:527.
  77. Crane JM, Van den Hof MC, Dodds L, et al. Maternal complications with placenta previa. Am J Perinatol 2000; 17:101.
  78. Fan D, Xia Q, Liu L, et al. The Incidence of Postpartum Hemorrhage in Pregnant Women with Placenta Previa: A Systematic Review and Meta-Analysis. PLoS One 2017; 12:e0170194.
  79. Clark, SL. Placenta previa and abruptio placentae. In: Creasy RK, Resnik R (Eds): Maternal Fetal Medicine: Principles and Practice. WB Saunders, Philadelphia 1999. p. 616.
  80. Abenhaim HA, Azoulay L, Kramer MS, Leduc L. Incidence and risk factors of amniotic fluid embolisms: a population-based study on 3 million births in the United States. Am J Obstet Gynecol 2008; 199:49.e1.
  81. Fong A, Chau CT, Pan D, Ogunyemi DA. Amniotic fluid embolism: antepartum, intrapartum and demographic factors. J Matern Fetal Neonatal Med 2015; 28:793.
  82. Spiliopoulos M, Puri I, Jain NJ, et al. Amniotic fluid embolism-risk factors, maternal and neonatal outcomes. J Matern Fetal Neonatal Med 2009; 22:439.
  83. Salihu HM, Li Q, Rouse DJ, Alexander GR. Placenta previa: neonatal death after live births in the United States. Am J Obstet Gynecol 2003; 188:1305.
  84. Vahanian SA, Lavery JA, Ananth CV, Vintzileos A. Placental implantation abnormalities and risk of preterm delivery: a systematic review and metaanalysis. Am J Obstet Gynecol 2015; 213:S78.
  85. Zlatnik MG, Cheng YW, Norton ME, et al. Placenta previa and the risk of preterm delivery. J Matern Fetal Neonatal Med 2007; 20:719.
  86. Schneiderman M, Balayla J. A comparative study of neonatal outcomes in placenta previa versus cesarean for other indication at term. J Matern Fetal Neonatal Med 2013; 26:1121.
  87. Jang DG, Jo YS, Lee SJ, Lee GS. Risk factors of neonatal anemia in placenta previa. Int J Med Sci 2011; 8:554.
  88. Vergani P, Ornaghi S, Pozzi I, et al. Placenta previa: distance to internal os and mode of delivery. Am J Obstet Gynecol 2009; 201:266.e1.