Placenta Previa

Published on 30/05/2015 by admin

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Last modified 30/05/2015

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Chapter 216 Placenta Previa

INTRODUCTION

Description: Placenta previa is implantation of the placenta in a location that leaves part or all of the cervical os covered. This is associated with potentially catastrophic maternal bleeding and obstruction of the uterine outlet. Several degrees are recognized: total, partial, marginal, and low-lying placenta. These degrees may vary with cervical dilation or gestational age.

Prevalence: Seen in 0.3% to 0.5% of deliveries.

Predominant Age: Reproductive, average age 29 years.

Genetics: No genetic pattern.

ETIOLOGY AND PATHOGENESIS

Causes: Implantation by the zygote low in the uterine cavity (in close proximity to the cervical os). Defective decidual vascularization, resulting from inflammation or atrophy, has been implicated.

Risk Factors: Multiparity, advanced maternal age (>35: 1% of deliveries, >40: 2%), prior cesarean delivery (two to five times increase), induced abortion, smoking (2-fold increase), cocaine use, multiple gestation, high altitude, and prior abortion.

CLINICAL CHARACTERISTICS

Signs and Symptoms

• Painless vaginal bleeding (70%, generally not present until late second or early third trimester); may be catastrophic in amount, although initial episodes are rarely fatal; blood is maternal in origin

• Uterine hyperactivity possibly present with bleeding (20%)

• Heavy or prolonged bleeding after delivery

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Netters Obstetrics and Gynecology