Usefulness of Magnetic Resonance Imaging in Antenatal Diagnosis of Vasa Previa: A Case Report

Vasa previa is a condition in which vessels unprotected by the umbilical cord or
placenta reside on the amniotic membranes and run in the vicinity of the internal
cervical os. Antenatal diagnosis is extremely important for the prognosis of the
fetus. The patient was a 27 year-old primiparous woman. At 33 weeks of gestation,
ultrasonography showed vessels were between the fetal head and the internal
cervical os, the placenta was implanted on the posterior wall, and the vessels could
be followed to the posterior surface of the bladder along the anterior uterine wall.
The site of umbilical cord insertion was difficult to assess by ultrasonography. MRI
showed a velamentous insertion that attached to the lower anterior wall near
the internal os, and the vessels were on the internal os. The fetal umbilical cord
vessels, which were not covered by Walton's jelly, were within 2 cm of the internal
cervical os. Vasa previa was diagnosed. At 33 weeks and 3 day of gestation, the
uterine contractions increased, and the patient underwent an emergency cesarean
section to prevent rupture of the vasa previa. The membranes were ruptured by
avoiding the vessels, and an 1872-g girl infant was delivered with Apgar scores of
7 and 8. Macroscopic assessment of the placenta and membranes demonstrated
vasa previa and velamentous insertion of the umbilical cord. MRI is useful not only
for the definitive diagnosis of the vasa previa but also for determining the position
of the uterine incision at the time of cesarean section.

Author(s):

Yara N, Kinjo T, Ohki Y, Kinjyo Y, Chinen Y, Nitta H, Masamoto H, Mekaru K and Aoki Y

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