Diagnostic ultrasound ( PDFDrive )

1468 PART IV Obstetric and Fetal Sonography
FIG. 43.4 Three-Dimensional Assessment of Placental Volume in Second Trimester.
Amniochorionic
membrane
Umbilical
vein
Chorionic
plate
Fetal
circulation
Umbilical
arteries
Intervillous
space Main stem
villus
Chorion
Amnion
Decidua
parietalis
Anchoring villus
Decidua
basalis
Myometrium
Endometrial Endometrial
veins arteries
Maternal circulation
FIG. 43.5 Schematic Drawing of Placental Vasculature.
directly the trophoblasts of the villi 28 (Fig. 43.5). Maternal blood
low of the intervillous space depends on low from the spiral
arteries. Maternal vascular disease (e.g., hypertension) can directly
afect the pregnancy by limiting this blood low. 29
Intervillous blood low begins early in the irst trimester. 30-32
Color Doppler ultrasound has been used to detect this intervillous
and spiral artery low by 12 weeks’ gestation, but the low, if any,
that occurs before this time is not well understood. 33 Before 12
weeks, the presence of intervillous blood low by gray-scale
imaging may indicate failed pregnancy. 34
Color and power Doppler sonography have been used to
identify blood low in intraplacental villous arteries. 35 A decrease
in the number of detectable intraplacental villous arteries is
associated with IUGR. 36 hree-dimensional power Doppler
ultrasound provides a better appreciation of placental vascularity
and pathophysiology by assessing placental low and documenting
the amount of low in a given area. Because of its low variability
between sampling sites in varied parts of the placenta, 3D imaging
may have a future role in assessing low in high-risk pregnancies
(e.g., hypertension, IUGR). 37 Recent work by multiple researchers
has shown that 3D placental vascularization indices are lower
for those with preeclampsia, 19 are not aided by the inclusion of
pregnancy-associated plasma protein A (PAPP-A) and uterine
artery Doppler indices, 38 and may be improved with the addition