Vasa previa refers to the presence of large placental vessels crossing the cervical opening ahead of the presenting part. These vessels are relatively fragile and sensitive to trauma, which may result in sudden hemorrhage or thrombosis. Fetal demise may occur if the condition is not recognized and managed appropriately.


Main associations for vasa previa:

(1) abnormal placentation

(2) abnormal insertion of the umbilical cord

(3) abnormal fertility

(3) abnormalities felt on physical examination


Abnormal placentation:

(1) bilobed placenta (2 separate disks of approximately equal size)

(2) succenturiate placenta (accessory disk)

(3) 3 or more plates (rare)

(4) low lying placenta (near the cervical canal)


Abnormal insertion of the umbilical cord:

(1) velamentous insertion

(2) marginal insertion


Abnormal fertility:

(1) multiple pregnancies (twins, triplets, etc.)

(2) pregnancy secondary to in vitro fertilization


Abnormal physical examination:

(1) palpable umbilical cord

(2) palpable structure thought to represent an amniotic band


The presence of one or more of these findings should prompt transvaginal Doppler ultrasonography.


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