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

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

INTRODUCTION

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 "Management of placenta previa".)

EPIDEMIOLOGY

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]:

                             

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Literature review current through: Jul 2017. | This topic last updated: Aug 04, 2017.
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