Diagnostic ultrasound ( PDFDrive )

1020 PART IV Obstetric and Fetal Sonography
FIG. 28.6 Omphalocele at 11 Weeks’ Gestational Age. Sagittal
view of fetus (calipers) shows a large, abdominal wall defect (arrow).
two levels of scanning is that the standard, basic, routine, or
level I examination is performed routinely on pregnant patients
(Figs. 28.7 to 28.15, Videos 28.3) to 28.9. he methods to obtain
all the required images are described in detail in subsequent
chapters. his chapter provides a collage of igures as a guide
for the anatomic survey and common additional views obtained
during a fetal survey.
In general, the “standard fetal anatomic survey” refers to
the second-trimester scan, typically performed between 16
and 22 weeks of gestation. When anatomic surveys are performed
at 20 to 22 weeks’ gestational age, there is less need
for repeat scans to document normal anatomy compared to
studies performed earlier in pregnancy. 12 However, there are
practical considerations when determining the optimal timing
of studies. In well-dated pregnancies in women who are unlikely
to want amniocentesis, a survey at 20 to 22 weeks’ gestation is
optimal. However, if a pregnancy is not well-dated, an earlier
scan may be needed both to establish accurate dates for the
pregnancy and to assess the anatomy. Some centers ofer the
scan at 16 weeks’ gestation to coincide with performance of
genetic amniocentesis and/or midtrimester quadruple serum
screening.
he level I examination consists of investigation of the
maternal uterus and ovaries, the cervix, and placenta (Fig.
28.7, Video 28.3), as well as a systematic review of fetal
anatomy. Adnexal cysts are common in pregnant women. In
early pregnancy a cyst is most likely the corpus luteum. If a
cyst appears atypical or enlarges beyond the middle second trimester,
it should be further assessed. Leiomyoma position and
size should be documented. If the myometrium appears thin
in the lower uterine segment (e.g., <3 mm in a woman with
prior cesarean section), the myometrium should be measured
with transvaginal sonography and should be followed later in
pregnancy because the thin myometrium puts the woman at
risk for uterine dehiscence and/or rupture. It is helpful to
begin the examination with a sagittal midline view to assess
the cervix. If the cervix appears abnormally short or if placenta
previa is suspected, a vaginal scan can then be performed.
Survey Guidelines for Second- and Third-Trimester Ultrasound
GENERAL SURVEY
Cardiac activity: document with M-mode
Presentation: cephalic, breech, transverse, variable
Fetal number: for multiples, amnionicity/chorionicity,
concordance with size, amniotic luid
Maternal anatomy: uterus, adnexa, and cervix
Gestational age and fetal weight assessment
Biparietal diameter
Head circumference
Abdominal circumference
Femur length
Amniotic luid
Estimate as normal
If abnormal, quantify if high or low
Placenta: position
FETAL ANATOMIC SURVEY
Head, Face, and Neck
Cerebellum
Choroid plexus
Cisterna magna
Lateral cerebral ventricles
Midline falx
Cavum septi pellucidi
Upper lip
Chest
Four-chamber view
Outlow tracts
Abdomen
Stomach (presence, size, and situs)
Kidneys, bladder
Umbilical cord insertion site into fetal abdomen
Umbilical cord vessel number
Spine
Cervical, thoracic, lumbar, and sacral
Extremities
Legs and arms
Genitalia (Sex)
In multiple gestations and when medically indicated
Modiied from Collaborative Subcommittee. ACR–ACOG–AIUM–SRU practice parameter for the performance of obstetrical ultrasound. American
College of Radiology; 2014. 5