Diagnostic ultrasound ( PDFDrive )

1018 PART IV Obstetric and Fetal Sonography
A
B
C
D E F
G H I
FIG. 28.3 First-Trimester Ultrasound Images: Embryo and Fetus. (A) Normal embryo at 6.5 weeks’ gestation. Note embryonic pole (calipers)
adjacent to yolk sac. (B) Normal embryo at 8 weeks’ gestation. Note embryo (calipers) and adjacent yolk sac (arrow). (C) M-mode ultrasound from
same embryo as in B. Note normal heart rate of 160 beats/min. (D) Normal embryo at 9 weeks’ gestational age. Note embryo within amnion
(arrow) and umbilical cord (arrowhead). (E) Just lateral to image in D, note yolk sac (arrowhead) is located outside the amnion (arrow). (F) Sagittal
ultrasound at 10.5 weeks’ gestation. (G) Sagittal ultrasound at 11.5 weeks’ gestation. (H) Coronal view of face at 13 weeks’ gestation. (I) Sagittal
ultrasound of nuchal translucency (calipers) at 13 weeks’ gestation. See also Videos 28.1 and 28.2.
DNA screening alone. 10 Patients should be counseled that a
negative cell-free DNA test result does not ensure an unafected
pregnancy. According to a 2015 ACOG committee opinion,
“Given the performance of conventional screening methods, the
limitations of cell-free DNA screening performance, and the
limited data on cost-efectiveness in the low-risk obstetric population,
conventional screening methods remain the most appropriate
choice for irst-line screening for most women in the general
obstetric population.” 10
hus despite increased use of cell-free DNA testing, ultrasound
screening is still being performed by measuring nuchal
translucency between 11 and 14 weeks of gestation (see Fig.
28.3I). his measurement, in conjunction with maternal age
and serology, can be used to determine an individualized risk
of fetal aneuploidy (see Chapter 31). Increased use of maternal
serum screening, as well as irst- and second-trimester ultrasound
have reduced the number of interventional procedures
to detect aneuploidy while increasing the number of prenatal
diagnoses of aneuploidy. 11 Given the increased scanning late in
the irst trimester, it is also increasingly common for a limited
anatomic survey to be conducted in the late irst trimester.
Anomalies that should be detected this early include anencephaly
(Fig. 28.5) and omphalocele (Fig. 28.6). Although
substantial information can be obtained at this time, the irsttrimester
anatomic survey is unlikely to replace the secondtrimester
anatomic survey, since many structures are diicult