Diagnostic ultrasound ( PDFDrive )

1484 PART IV Obstetric and Fetal Sonography
but management is unclear, especially because documenting
circumferential looping of the umbilical cord around the fetal
neck is diicult because of the shadowing present late in
gestation.
he normal umbilical cord has three vessels; one vein carries
oxygenated blood to the fetus, and two arteries carry deoxygenated
blood from the fetus. In 1% to 2% of pregnancies, however, there
is only a single umbilical artery (Fig. 43.30, Video 43.15). he
diagnosis is made either by examining a free loop of cord in
the amniotic luid or by assessing the umbilical arteries around
FIG. 43.29 Edematous Cord. Transabdominal sonogram of a thirdtrimester
fetus shows an edematous area (arrow) of cord near the
abdominal umbilical cord insertion.
the fetal bladder. Although associated with aneuploidy as well as
many anomalies, especially renal and cardiac abnormalities, in
isolation a single umbilical artery has no functional importance.
Insertion Into the Placenta
he normal umbilical cord normally inserts into the central
portion of the placenta. Identifying the placental umbilical cord
insertion is important to recognize abnormalities of the umbilical
cord vessels, as with gray-scale imaging and color or power
Doppler sonography 165 (Fig. 43.31, Video 43.16).
Velamentous and Marginal Cord Insertions
A velamentous umbilical cord insertion refers to the situation
where the umbilical cord inserts into the membranes and not
the placental disc (Fig. 43.32, Video 43.15). A marginal cord
insertion (Fig. 43.33), also known as a battledore placenta,
occurs when the umbilical cord inserts into the very margin of
the placenta. Velamentous umbilical cord insertions occur in
approximately 1% of singleton pregnancies; marginal cord insertions
occur in approximately 7% of singletons. Both of these
cord insertions are more common in multiple gestations and
are also associated with single umbilical arteries 28 and are associated
with the smaller twins in monochorionic twin pregnancies
with discordant growth. 166
Velamentous umbilical cord insertions are sonographically
identiied throughout the second and third trimesters of pregnancy
with great reliability. Sepulveda et al. 167 identiied the placental
cord insertion in more than 99% of pregnancies, correctly
identifying all velamentous cord insertions using both gray-scale
and color Doppler sonography. 167 A velamentous cord insertion
has been identiied as early as 10 weeks’ gestation 168 and can be
routinely identiied on the 11- to 14-week irst-trimester scan. 169
Velamentous cord insertions are associated with IUGR, preterm
delivery, congenital anomalies, low Apgar scores, fetal and
A
B
FIG. 43.30 Single Umbilical Artery. (A) Gray-scale sonogram shows a single artery and a single vein. (B) Color Doppler ultrasound adjacent
to the fetal bladder shows a single umbilical artery. See also Video 43.15.