Diagnostic ultrasound ( PDFDrive )

1384 PART IV Obstetric and Fetal Sonography
A B C
FIG. 40.7 Campomelic Dysplasia and Pulmonary Hypoplasia. Coronal ultrasound images of the thorax in triplet pregnancy at 27 weeks’
gestation. (A) Normal triplet A shows normal convex contour of the thorax. Calipers measure the scapula. (B) Triplet B shows a bell-shaped
thorax. (C) Radiograph of triplet B conirms a bell-shaped thorax consistent with pulmonary hypoplasia.
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Dizygotic twin pregnancies are at similar risk for skeletal
abnormalities as singleton pregnancies, and the frequency is
increased two to three times in monozygotic twins. Both monozygotic
and dizygotic twins can be discordant for genetic and
nongenetic skeletal abnormalities. Twin pregnancies are generally
discordant and overall, about 15% of twins are concordant for
the same anomaly. 40,41
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FIG. 40.8 Normal Ribs: Three-Dimensional Ultrasound.
and dysplasia, limb defects), campomelic dysplasia, and chromosome
abnormalities. hree-dimensional ultrasound volume images
aid in accurately counting the number of ribs (Fig. 40.8).
Ultimately, a detailed examination of each bone may be
required to determine the fetal condition. Speciic dysmorphic
features of bones (e.g., clavicular or scapular hypoplasia; aplasia
of ibula, tibia, or radius; platyspondyly) can be helpful to further
deine a speciic skeletal dysplasia. A detailed evaluation of the
cardiovascular, genitourinary, gastrointestinal, and central nervous
system should be done concurrently with the musculoskeletal
evaluation.
Additional Diagnostic Techniques
Three-Dimensional Ultrasound
hree-dimensional ultrasound is becoming an increasingly
useful complement to two-dimensional ultrasound in diagnosis
of skeletal dysplasia and pulmonary hypoplasia. High-contrast
structures such as the fetal skeleton are especially amenable to
three-dimensional ultrasound-rendering sotware and postprocessing
techniques. 42 Surface-rendering capabilities are
particularly useful for visualizing subtle facial dysmorphism
(such as low-set or deformed ears, micrognathia, or lattening of
the facial proile associated with midface hypoplasia), evaluating
cranial distortion due to craniosynostosis, or assessing hand and
foot abnormalities. 43 However, there are insuicient published
data to gauge the diagnostic performance of this modality 44-46
(Fig. 40.9).
Radiography
he role of prenatal radiography is limited. Typically, two ilms
might be performed: an anteroposterior view, placing the fetus
over the hollow of the pelvis, and an angulated view, with the
fetus projected down, away from the maternal sacrum. he
appearance of short limbs of normal shape and the presence of
growth recovery lines can be useful in distinguishing severe IUGR
from a skeletal dysplasia. 31 In contrast, postnatal radiography
plays an extremely important role in deining the characteristic
radiologic features found in many skeletal anomalies.
Three-Dimensional Computed Tomography
hree-dimensional low-dose computed tomography (CT) may
have a better diagnostic yield than two-dimensional ultrasound