2. Sonography in obstetrics
• A great hallmark in obstetrical history began in the second half of the
20th century with the ability to image the pregnant uterus and its
contents
• Sonography in prenatal care includes first- and second trimester fetal
anatomic evaluation and specialized studies performed to
characterize abnormalities.
• National Institute of Child Health and Human Development (NICHD)
workshop concluded that “every fetus deserves to have a physical
examination” (Reddy, 2008)
3. Technology
• Ultrasound refers to sound waves traveling at a frequency above
20,000 hertz (cycles per second)
• The real-time image on the ultrasound screen is produced by sound
waves that are reflected back from fluid and tissue interfaces of the
fetus, amnionic fluid, and placenta.
• Digital images generated at 50 to more than 100 frames per second
undergo postprocessing that yields the appearance of real-time
imaging
• Higher-frequency transducers yield better image resolution, whereas
lower frequencies penetrate tissue more effectively
4. Foetal Safety
• The use of sonography for any nonmedical purpose, is considered
contrary to responsible medical practice and is not condoned by the
FDA and the American Institute of Ultrasound in Medicine (2012,
2013a)
• Prolonged ultrasound exposure may affect brain cell migration in fetal
mice (Rakic, 2006).
• However, no causal relationship has been demonstrated between
diagnostic ultrasound and recognized adverse effects in human
pregnancy
• All sonography machines are required to display two indices: the
thermal index and the mechanical index.
6. First-Trimester Sonography
• An intrauterine gestational sac is reliably visualized with transvaginal
sonography by 5 weeks, and an embryo with cardiac activity by 6
weeks.
• The embryo should be visible transvaginally once the mean sac
diameter has reached 20 mm—otherwise the gestation is
anembryonic
• Cardiac motion is usually visible with transvaginal imaging when the
embryo length has reached 5 mm
• At Parkland hospital, first-trimester demise is diagnosed if the embryo
has reached 10 mm without cardiac motion, taking into consideration
the standard error of the ultrasound measurements.
9. First-Trimester Fetal Anomaly Detection
• Research in this area has focused on anatomy visible at 11 to 14
weeks, to coincide with sonography performed as part of aneuploidy
screening
• A study of systematic anatomy evaluation between 11 and 14 weeks
yielded a detection rate of approximately 40 percent for non-
chromosomal abnormalities
• Identification varies considerably according to the specific
abnormality
• Thus, as first-trimester sonography is unreliable for detection of many
major abnormalities, it should not replace second-trimester
anatomical evaluation.
10. Second- and Third-Trimester Sonography
• There are three types of examinations: standard, specialized, and
limited
• Standard sonographic examination is the most commonly performed
• The fetal anatomical structures may be adequately assessed after
approximately 18 weeks
• There are several types of specialized examinations.
• The targeted examination is a detailed anatomical survey performed
when an abnormality is suspected on the basis of history, screening
test result, or abnormal findings from a standard examination
• A limited examination is performed to address a specific clinical
question
13. Foetal Biometry
• The estimates are most accurate when multiple parameters are used
and when nomograms derived from fetuses of similar ethnic or racial
background living at similar altitude are selected.
• Even the best models may over- or underestimate fetal weight by as
much as 15 percent (American Institute of Ultrasound in Medicine,
2013a
15. Foetal Biometry
• Menstrual dates are generally considered confirmed if an estimated
gestational age (EGA) based on a sonographic first-trimester crown-
rump length is within 1 week
• or if the EGA from biometry at 14 to 20 weeks is within 10 days
(ACOG, 2011).
• In the third trimester, the accuracy of sonography is only within 3 to 4
weeks.
• Sonographic evaluation performed to monitor fetal growth should
typically be performed at least 2 to 4 weeks after a prior examination
(American Institute of Ultrasound in Medicine, 2013a).
16. Amnionic Fluid
• Amnionic fluid volume evaluation is a component of every second- or
third-trimester sonogram
• Oligohydramnios indicates that the volume is below normal range
• Hydramnios—also called polyhydramnios—is defined as amnionic
fluid volume above normal
• Measurements include either the single deepest vertical fluid pocket
or the sum of the deepest vertical pockets from each of four equal
uterine quadrants—the amnionic fluid index
• Deepest vertical pocket is normally between 2 and 8 cm, and the
amnionic fluid index normally ranges between 8 and 24 cm.
17. Fetal Anatomical Evaluation
• An important goal of second- and third-trimester sonography is to
systematically evaluate fetal anatomy.
• If a single ultrasound examination is planned for the purpose of
evaluating fetal anatomy, the ACOG(2011) recommends that it be
performed at 18 to 20 weeks
• If imaging is suboptimal, a follow-up examination may be helpful.
• If an abnormality is identified or suspected during a standard
examination of fetal anatomy, specialized sonography is indicated.
18. Second-Trimester Fetal Anomaly Detection
• The sensitivity of sonography for detecting fetal anomalies varies
according to factors such as gestational age, maternal habitus, fetal
position, equipment features, examination type, operator skill, and
the specific abnormality in question
• Every sonographic examination should include a frank discussion of
examination limitations
• The sensitivity of specialized sonography in experienced centers is
considered to be at least 80 percent (ACOG, 2011)
• Most anomalous infants—approximately 75 percent—occur in
pregnancies that are otherwise low-risk, that is, without an indication
for specialized sonography
19. NORMAL AND ABNORMAL FETAL ANATOMY
Brain and Spine
• Standard sonographic evaluation of the fetal brain includes three
transverse (axial) views
• The transthalamic view is used to measure the BPD and HC and includes
the midline falx, cavum septum pellucidum (CSP), and thalami
• The transventricular view includes the lateral ventricles, which contain the
echogenic choroid plexus
• The transcerebellar view is obtained by angling the transducer back
through the posterior fossa
• Imaging of the spine includes evaluation of the cervical, thoracic, lumbar,
and sacral regions
23. Neural-Tube Defects
• These result from incomplete closure of the neural tube by the
embryonic age of 26 to 28 days
• They are the second most common class of malformations after
cardiac anomalies
• Their prevalence was previously considered to be 1.4 to 2 per 1000
births
• Neural tube defects can be prevented with folic acid supplementation
• When isolated, neural-tube defect inheritance is multifactorial, and
the defect recurrence risk without periconceptional folic acid
supplementation is 3 to 5 percent
28. Agenesis of the Corpus Callosum
• The corpus callosum is the major fiber bundle connecting reciprocal
regions of the cerebral hemispheres and the frontal horns are
displaced laterally
• Also, there is mild enlargement of the atria posteriorly— such that
the ventricle has a characteristic “teardrop” appearance
• Prevalence of agenesis of the corpus callosum is 1 in 5000 births
• If the anomaly was still considered isolated following MR imaging,
normal developmental outcome was reported in 75 percent of cases,
and severe disability in 12 percent
29. Holoprosencephaly
• In early normal brain development, the prosencephalon or forebrain
divides into the telencephalon and diencephalon
• With holoprosencephaly, the prosencephalon fails to divide
completely into two separate cerebral hemispheres and into
underlying diencephalic structures
• The birth prevalence of holoprosencephaly is only 1 in 10,000 to
15,000.
• However, the abnormality has been identified in nearly 1 in 250 early
abortuses
32. Sacrococcygeal Teratoma
• This germ cell tumor is one of the most common tumors in neonates,
with a birth prevalence of approximately 1 per 28,000 (Derikx, 2006;
Swamy, 2008)
• It is believed to arise from the totipotent cells along Hensen node,
anterior to the coccyx.
• The tumor may be mature, immature, or malignant
• Internal pelvic components may be more challenging to visualize, and
fetal MR imaging should be considered.
• Fetuses with tumors > 5 cm often require cesarean delivery, and
classical hysterotomy may be needed (Gucciaro, 2011)
33. Caudal Regression Sequence—Sacral Agenesis
• This rare anomaly is characterized by absence of the sacral spine and
often portions of the lumbar spine
• It is approximately 25 times more common in pregnancies with
pregestational diabetes (Garne, 2012).
• Sonographic findings include a spine that appears abnormally short,
lacks the normal lumbosacral curvature, and terminates abruptly
above the level of the iliac wings.
34. Face and Neck
• A fetal profile is not a required component of standard examination
but may be helpful in identifying cases of micrognathia
• Micrognathia should be considered in the evaluation of hydramnios
Facial Clefts (There are three main types of clefts)
• The first type, cleft lip and palate
• The second type of cleft is isolated cleft palate
• A third type of cleft is median cleft lip
38. Thorax
• The lungs appear as homogeneous structures surrounding the heart
and are best visualized after 20 to 25 weeks’ gestation
• In the four-chamber view of the chest, they comprise approximately
two thirds of the area, with the heart occupying the remaining third
• The thoracic circumference is measured at the skin line in a transverse
plane at the level of the four-chamber view
• Various abnormalities may be seen sonographically as cystic or solid
space-occupying lesions.
39. Congenital Diaphragmatic Hernia
• This is a defect in the diaphragm through which abdominal organs herniate
into the thorax.
• It is left-sided in approximately 75 percent of cases, right-sided in 20
percent, and bilateral in 5 percent (Gallot, 2007)
• The prevalence of congenital diaphragmatic hernia (CDH) is approximately
1 per 3000 to 4000 births
• Associated anomalies and aneuploidy occur in 40 percent of cases
• In population-based series, the presence of an associated abnormality
reduces the overall survival rate of neonates with diaphragmatic hernia
from approximately 50 percent to about 20 percent
• In the absence of associated abnormalities, the major causes of mortality
are pulmonary hypoplasia and pulmonary hypertension
41. Congenital Cystic Adenomatoid Malformation
• This abnormality represents hamartomatous overgrowth of terminal
bronchioles that communicates with the tracheobronchial tree
• It is also called CPAM—congenital pulmonary airway malformation,
based on an understanding that not all histopathologic types are
cystic or adenomatoid
• The prevalence is estimated to be 1 per 6000 to 8000 births
• Sonographically, congenital cystic adenomatoid malformation (CCAM)
is a well-circumscribed thoracic mass that may appear solid and
echogenic or may have one or multiple variably sized cysts
42.
43. Extra-lobar Pulmonary Sequestration
• Also called a bronchopulmonary sequestration, this abnormality is an
accessory lung bud “sequestered” from the tracheobronchial tree,
that is, a mass of non-functioning lung tissue
• Most cases diagnosed prenatally are extra-lobar, which means they
are enveloped in their own pleura
• Overall, however, most sequestrations present in adulthood and are
intra-lobar—within the pleura of another lobe
• Lesions have a left-sided predominance and most often involve the
left lower lobe
44. Congenital High Airway Obstruction Sequence
(CHAOS)
• This rare anomaly usually results from laryngeal or tracheal atresia
• The normal egress of lung fluid is obstructed, and the
tracheobronchial tree and lungs become massively distended
• Sonographically, the lungs appear brightly echogenic, and the bronchi
are dilated with fluid
• Flattening and eversion of the diaphragm is common, as is
compression of the heart.
• Venous return is impaired and ascites develops, typically followed by
hydrops
46. Heart
• Cardiac malformations are the most common class of congenital
anomalies, with an overall prevalence of 8 per 1000 births
• Almost 90 percent of cardiac defects are multifactorial or polygenic in
origin
• The most frequent chromosomal abnormality found in those with a heart
defect is trisomy 21
• Traditionally, detection of congenital cardiac anomalies has been more
challenging than anomalies of other organ systems
47. Basic Cardiac Examination
• Standard cardiac assessment includes a four-chamber view
• Evaluation of rate and rhythm, and evaluation of the left and right
ventricular outflow tracts
• Evaluation of the cardiac outflow tracts may aid in detection of
abnormalities not initially appreciated in the four-chamber view.
• These may include tetralogy of Fallot, transposition of the great
vessels, or truncus arteriosus.
51. Ventricular Septal Defect.
• This is the single most common congenital cardiac anomaly and
occurs in approximately 1 per 300 births
• Even with adequate visualization, the prenatal detection rate of
ventricular septal defect (VSD) is low
• A defect may be appreciated in the membranous or muscular portion
of the interventricular septum in the four-chamber view, and color
Doppler demonstrates flow through the defect.
• Fetal VSD is associated with aneuploidy, particularly with coexistent
other congenital abnormalities, and fetal karyotyping should be
offered
52. Endocardial Cushion Defect.
• This is also called an atrioventricular (AV) septal defect or AV canal defect.
• It develops in approximately 1 per 2500 births and is associated with
trisomy 21 in more than half of cases
• The endocardial cushions are the crux of the heart, and defects jointly
involve the atrial septum primum, interventricular septum, and medial
leaflets of the mitral and tricuspid valves
• Endocardial cushion defects associated with heterotaxy are more likely to
have conduction system abnormalities resulting in third-degree AV block
53. Hypoplastic Left Heart Syndrome
• This anomaly occurs in approximately 1 per 4000 births
• Once considered a lethal prognosis, it is now estimated that 70
percent of infants may survive to adulthood
• Morbidity remains high, and developmental delays are common.
• Sonographically, the left side of the heart may appear so small that it
is difficult to appreciate a ventricular chamber.
• There may be no visible inflow or outflow and may be reversal of flow
in the ductus arteriosus
54. Tetralogy of Fallot
• This anomaly occurs in approximately 1 per 3500 births
• It is characterized by four components: ventricular septal defect, an
overriding aorta, pulmonary valve abnormality, and right ventricular
hypertrophy
• The last does not present before birth
• The prognosis following postnatal repair is usually excellent, and 20-
year survival rates exceed 95 percent
• Cases with pulmonary atresia have a more complicated course
55. Cardiac Rhabdomyoma
• This is the most common cardiac tumor.
• Approximately 50 percent of cases are associated with tuberous
sclerosis, an autosomal dominant disease with multiorgan system
manifestations
• Cardiac rhabdomyomas appear as well-circumscribed echogenic
masses, usually within the ventricles or outflow tracts
• There may be one or multiple; they may increase in size during
gestation; and occasionally, inflow or outflow obstruction may result
• In the absence of obstruction or very large size, the prognosis is
relatively good from a cardiac standpoint.
56. M-Mode
• Motion-mode imaging is a linear display of cardiac cycle events, with
time on the x-axis and motion on the y-axis
• It is used frequently to measure fetal heart rate
• If there is an abnormality of heart rate or rhythm, M-mode imaging
permits separate evaluation of atrial and ventricular waveforms
• Thus, it is particularly useful for characterizing arrhythmias and their
response to treatment
• M-mode can also be used to assess ventricular function and atrial and
ventricular outputs.
58. Premature Atrial Contractions.
• Called atrial extrasystoles, these are the most common fetal
arrhythmia
• They represent cardiac conduction system immaturity and typically
resolve later in gestation or in the neonatal period
• Premature atrial contractions are not associated with major structural
cardiac abnormalities, although they sometimes occur with an atrial
septal aneurysm
• 2 percent, affected fetuses are later identified to have a
supraventricular tachycardia (SVT) that requires urgent treatment
59. Abdominal Wall
• Gastroschisis and omphalocele, collectively termed ventral wall
defects, are relatively common fetal anomalies.
Gastroschisis
• Full-thickness abdominal wall defect typically located to the right of
the umbilical cord insertion
• The prevalence is 1 per 2000 to 4000 pregnancies
• Gastroschisis is the one major anomaly more common in fetuses of
younger mothers, and the average maternal age is 20 year
• Gastroschisis is not associated with an increased risk for aneuploidy,
and the survival rate approximates 90 percent
61. Abdominal Wall
Omphalocele
• This anomaly complicates approximately 1 per 3000 to 5000
pregnancies
• In more than half of cases, omphalocele is associated with other
major anomalies or aneuploidy
• It also is a component of syndromes such as Beckwith–Wiedemann,
cloacal exstrophy, and pentalogy of Cantrell.
• Smaller defects confer an even greater risk for aneuploidy
• Like other major anomalies, identification of an omphalocele
mandates a complete anatomical evaluation, and fetal karyotyping is
recommended
63. Body Stalk Anomaly
• Also known as limb-body-wall complex or cyllosoma
• This is a rare, lethal anomaly characterized by abnormal formation of
the body wall coelom
• There is close approximation or fusion of the body to the placenta,
and an extremely short umbilical cord
• Acute angle scoliosis is another feature. Amnionic bands are often
identified.
64. Gastrointestinal Tract
• The stomach is visible in nearly all fetuses after 14 weeks’ gestation
• The liver, spleen, gallbladder, and bowel can be identified in many
second- and third-trimester fetuses.
• If the stomach is not seen on an initial evaluation, the examination
should be repeated, and targeted sonography should be considered.
• Non-visualization of the stomach may be secondary to impaired
swallowing.
• And, underlying causes may include esophageal atresia, a craniofacial
abnormality, or a CNS or musculoskeletal abnormality such as
arthrogryposis
65. Gastrointestinal Atresia
• Bowel atresia is characterized by obstruction and proximal bowel
dilatation
• In general, the more proximal the obstruction, the more likely it is to
be associated with hydramnios
• This may at times necessitate large volume amniocentesis, also
termed amnioreduction
• Esophageal atresia occurs in approximately 1 in 4000 births
• More than half have associated anomalies and/or genetic syndromes
66. Gastrointestinal Atresia
• Duodenal atresia occurs in approximately 1 in 10,000 births
• It is characterized by the sonographic double-bubble sign, which
represents distention of the stomach and the first part of the
duodenum
• This finding is usually not present before 22 to 24 weeks’ gestation
• Approximately 30 percent of affected fetuses have an associated
chromosomal abnormality or genetic syndrome, particularly trisomy
21
68. Kidneys and Urinary Tract
• The fetal kidneys are visible adjacent to the spine, frequently in the
first trimester and routinely by 18 weeks’ gestation
• The length of the kidney is about 20 mm at 20 weeks, increasing by
approximately 1.1 mm each week thereafter
• With advancing gestation, the kidneys become relatively less
echogenic, and a rim of perinephric fat aids visualization of their
margins.
• Fetal urine production increases from 5 mL/hr at 20 weeks to
approximately 50 mL/hr at term
69. Renal Pelvis Dilatation
• This finding is present in 1 to 5 percent of fetuses.
• In 40 to 90 percent of cases, it is transient or physiological and does
not represent an underlying abnormality
• In approximately a third of cases, a urinary tract abnormality is
confirmed in the neonatal period.
• Most frequently, this is either ureteropelvic junction (UPJ) obstruction
or vesicoureteral reflux (VUR).
• Although various thresholds have been defined, the pelvis is typically
considered dilated if it exceeds 4 mm in the second trimester or 7 mm
in the third trimester
72. Duplicated Renal Collecting System
• This occurs when the upper and lower poles of the kidney—called
moieties—are each drained by a separate ureter
• Duplication is more common in females and is bilateral in 15 to 20
percent of cases
• It is recognized in approximately 1 per 4000 pregnancies
• Sonographically, an intervening tissue band separates two distinct
renal pelves.
73. Renal Agenesis
• The prevalence of bilateral renal agenesis is approximately 1 per 8000
births, whereas that of unilateral renal agenesis is 1 per 1000 birth
• When a kidney is absent, the ipsilateral adrenal gland typically
enlarges to fill the renal fossa, termed the lying down adrenal sign
• In addition, color Doppler imaging of the descending aorta will
demonstrate absence of the renal artery
• If renal agenesis is bilateral, no urine is produced. The resulting
anhydramnios leads to pulmonary hypoplasia, limb contractures, and
a distinctively compressed face
74. Multi-cystic Dysplastic Kidney
• This severe form of renal dysplasia results in a nonfunctioning kidney.
• The nephrons and collecting ducts do not form normally, such that
primitive ducts are surrounded by fibromuscular tissue, and the
ureter is atretic
• Sonographically, the kidney contains numerous smooth-walled cysts
of varying size that do not communicate with the renal pelvis and are
surrounded by echogenic cortex
• Unilateral multicystic dysplastic kidney (MCDK) has a prevalence of 1
per 4000 births.
• Bilateral MCDK develops in approximately 1 per 12,000 birth
75. Polycystic Kidney Disease
• Of the hereditary polycystic diseases, only the infantile form of
autosomal recessive polycystic kidney disease (ARPKD) may be
reliably diagnosed prenatally
• ARPKD is a chronic, progressive disease that involves the kidneys and
liver.
• It results in cystic dilatation of the renal collecting ducts and
congenital hepatic fibrosis
• Severe oligohydramnios confers a poor prognosis
• Autosomal dominant polycystic kidney disease (ADPKD), which is far
more common, usually does not manifest until adulthood
76. Bladder Outlet Obstruction
• Distal obstruction of the urinary tract is more frequent in male
fetuses, and the most common etiology is posterior urethral valves
• Characteristically, there is dilatation of the bladder and proximal
urethra, termed the “keyhole” sign, and the bladder wall is thick
• Oligohydramnios, particularly before mid pregnancy, portends a poor
prognosis because of pulmonary hypoplasia.
77. Skeletal Abnormalities
• The 2010 revision of the Nosology and Classification of Genetic
Skeletal Disorders includes an impressive 456 skeletal abnormalities in
40 groups that are defined by molecular, biochemical, and/or
radiographic criteria
There are two types of skeletal dysplasias:
• Osteochondrodysplasias—the generalized abnormal development of
bone and/or cartilage,
• and dysostoses—which are abnormalities of individual bones, for
example, polydactyly.
78. Skeletal Dysplasias
• The prevalence of skeletal dysplasias approximates 3 per 10,000
births.
• Evaluation of a pregnancy with suspected skeletal dysplasia includes a
survey of every long bone
• As well as the hands and feet, skull size and shape, clavicles, scapulae,
thorax, and spine
79. Clubfoot—Talipes Equinovarus
• This disorder is notable for a deformed talus and shortened Achilles
tendon.
• The affected foot is abnormally fixed and positioned with equinus—
downward pointing, varus—inward rotation, and forefoot adduction
• Most cases are considered malformations, with a multifactorial
genetic component.
• Sonographically, the footprint is visible in the same plane as the tibia
and fibula
• Clubfoot is approximately 1 per 1000 births, with a male:female ratio
of 2:1
80. Limb-Reduction Defects
• Documentation of the arms and legs is a component of the standard
examination.
• A limb-reduction defect is the absence of all or part of one or more
extremities
• Absence of an entire extremity is termed amelia
• Limb-reduction defects are associated with numerous genetic
syndromes, such as Roberts syndrome, an autosomal recessive
condition characterized by tetraphocomelia
• Limb-reduction defects may occur in the setting of a disruption such
as amnionic band sequence
