Diagnostic ultrasound ( PDFDrive )

CHAPTER 28 Overview of Obstetric Imaging 1017
A
B
C
FIG. 28.1 Normal First-Trimester Ultrasound Images: Pregnancy
Location and Adnexa. (A) Transabdominal sagittal sonogram shows an
intrauterine gestational sac. (B) Transverse image to the left of uterus
shows normal appearance for the ovary (arrow). (C) Transvaginal color
Doppler image shows normal hypervascular rim around corpus luteum.
FIG. 28.2 Normal First-Trimester Measurement of Sac Diameter.
Transvaginal sagittal image shows sagittal measurement of sac
diameter (calipers). Measurements in three orthogonal planes are averaged
to calculate the mean sac diameter. Note yolk sac within the gestational
sac.
variety of medical professionals performing and interpreting
ultrasound in a variety of clinical settings, thresholds for the
diagnosis of a failed pregnancy have been increased in order to
not misdiagnose a potentially viable pregnancy. hese issues are
discussed in detail in Chapter 30.
In cases of multiple gestation, irst-trimester scans should
document the fetal number as well as the amnionicity and
chorionicity (Fig. 28.4). Chapter 32 discusses the assessment of
multifetal pregnancies.
In addition, the American College of Obstetricians and
Gynecologists (ACOG) recommends that prenatal testing for
aneuploidy be ofered to all pregnant women. 10 Clinicians must
understand current screening options (and the tradeofs between
them), including traditional serum analysis (with or without
nuchal translucency ultrasonography) or cell-free DNA so that
they can discuss these options appropriately with the patient.
Cell-free DNA testing uses DNA from the placenta to assess the
risk of the fetus having a chromosomal abnormality; it does not
assess risk for fetal anomalies such as neural tube defects or
ventral wall defects. Management decisions, including termination
of the pregnancy, should not be based on the results of the cell-free