Article Sections

Introduction

Vasa previa is a rare condition in which unprotected fetal vessels overlie the internal cervical os.  These vessels are prone to injury and bleeding, leading to potentially severe and unpredictable complications (eg, fetal exsanguination); the risk for vessel injury and bleeding is particularly high during labor and delivery.

Pathophysiology

Normal fetal vessels travel in the umbilical cord surrounded by thick, gelatinous tissue (Wharton jelly), which provides protection.

Vasa previa is an aberrant condition in which the fetal vessels are unprotected (because they are surrounded only by thin fetal membranes) and overlie the internal cervical os ( Figure 1).  As a result, the vessels are exposed and prone to compression (leading to fetal asphyxiation) or tearing and subsequent bleeding (leading to fetal exsanguination).

The timing of vasa previa rupture is unpredictable, but the risk is particularly high during labor and delivery because cervical dilation, uterine contractions, and rupture of membranes can easily injure the fetal vessels.

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