Clinical features, diagnosis, and course of placenta previa
- Charles J Lockwood, MD, MHCM
Charles J Lockwood, MD, MHCM
- Section Editor — Obstetrics
- Senior Vice President, USF Health
- Dean, Morsani College of Medicine
- Professor, Obstetrics and Gynecology
- University of South Florida
- Karen Russo-Stieglitz, MD
Karen Russo-Stieglitz, MD
- Consulting Perinatologist
- Morristown Medical Center
- Section Editors
- Deborah Levine, MD
Deborah Levine, MD
- Section Editor — Imaging
- Professor of Radiology
- Director of Ob/Gyn Ultrasound
- Department of Radiology
- Beth Israel Deaconess Medical Center
- Susan M Ramin, MD
Susan M Ramin, MD
- Section Editor — Obstetrics
- Professor of Obstetrics and Gynecology
- Baylor College of Medicine
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 woman beyond 20 weeks of gestation who presents with painless vaginal bleeding. For women who have not had a second trimester ultrasound examination, antepartum 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.
INCIDENCE AND RISK FACTORS
In a systematic review including 58 observational studies of placenta previa, incidence ranged from 3.5 to 4.6 per 1000 births . The incidence is severalfold higher early in gestation, but most of these cases resolve before delivery (see 'Ultrasound presentation and course' below).
Purported risk factors, some of which are interdependent, include [2-13]:
●Previous placenta previa
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- INCIDENCE AND RISK FACTORS
- CLINICAL FEATURES
- Ultrasound presentation and course
- Associated conditions
- - Transabdominal
- - Transvaginal
- Magnetic resonance imaging
- DIFFERENTIAL DIAGNOSIS
- Exclusion of placenta accreta
- MORBIDITY AND MORTALITY
- INFORMATION FOR PATIENTS
- SUMMARY AND RECOMMENDATIONS