Diagnostic ultrasound ( PDFDrive )

CHAPTER 28 Overview of Obstetric Imaging 1021
A
B
C
D
FIG. 28.7 Overview of Uterus, Cervix, and Fetal Position. (A) Sagittal sonogram of uterus shows a normal-appearing cervix (C) and an anterior
placenta (P), with the placental tip far away from the internal cervical os. B, Bladder. (B) Transverse sonogram of posterior placenta (P). (C)
Transabdominal image of normal-appearing cervix (arrow on internal os). Note bladder (B) and fetal head (H). With the head as the presenting part,
the fetus is in cephalic position. (D) Transvaginal sonogram of normal-appearing cervix (calipers). See also Video 28.3.
Transverse and longitudinal scans of the entire uterine cavity
are then performed for assessment of fetal cardiac activity, amniotic
luid volume, localization of the placenta, and determination
of fetal presentation and situs (Fig. 28.8). Knowledge of the
plane of section across the maternal abdomen, combined with
the position of the fetal spine and right-sided and let-sided
structures within the fetal body, allows accurate determination
of fetal position and identiication of normal and pathologic
anatomy. Some congenital anomalies, such as dextrocardia, will
be recognized only if a structure is identiied as “abnormal” by
virtue of its atypical position related to the position of the fetus.
Biometry is performed to estimate gestational age and fetal
weight (Fig. 28.9). Assessment of gestational age in the second
and third trimesters is discussed in more detail in Chapter 42.
Additional views in routine obstetric sonography include the
head and face (Fig. 28.10, Video 28.4), heart (Fig. 28.11, Videos
28.5 and 28.6), abdomen and pelvis (Fig. 28.12, Video 28.7),
spine (Fig. 28.13, Video 28.8), extremities (Fig. 28.14), and
umbilical cord (Fig. 28.15, Video 28.9).
Other specialized sonographic examinations include fetal
Doppler sonography, biophysical proile, fetal echocardiography,
and additional biometric measurements.
he high-risk, targeted, detailed, or level II scan should have
a speciic indication that requires a detailed fetal sonogram,
performed by a clinician with expertise in obstetric imaging. 13,14
his high-risk scan is performed when an anomaly is suspected