Prenatal US Findings Flashcards
What is the definition of a soft marker?
variations in normal anatomy that alone are unlikely to be of clinical significance
Provide examples of what a soft marker is.
hypoplastic nasal bone enlarged nuchal fold mild ventriculomegaly short humerus choroid plexus cyst echogenic bowel short femur intracardiac echogenic focus
What soft markers can we see on first trimester US?
increased nuchal translucency
cystic hygroma
absent or hypoplastic nasal bone
abdominal wall defects
What soft markers can be seen on second trimester US?
nuchal fold
echogenic intracardiac focus (IEF)
choroid plexus cyst
echogenic bowel
What is a nuchal translucency?
sonographic appearance of a collection of fluid under the skin behind the fetal neck
NT alone detects approximately _____% of fetuses with trisomy 21.
70
A NT of ____ mm is abnormal in the first trimester screening regardless of serum analytes.
3.5
What is a cystic hygroma?
lymphatic abnormal at neck extendign down fetal back of anterior wall (variation of increased nuchal translucency)
What size of NT is normally associated with Down Syndrome?
3-4 mm
What size of NT is normally associated with 45,X?
very large (7 mm, cystic hygroma)
What should you offer a patient whose fetus has an increased NT in the first trimester?
CVS (do not draw blood)
FISH, karyotype, array for all cases
Noonan panel (for CH or NT > 4 mm)
NIPT not recommended as first tier testing
fetal anatomical survey and fetal ECHO
additional genetic testing considered based on 2nd trimester US
Increased NT is almost always _____. What does this mean for the risk of the fetus?
transient
risk of fetal abnormality is NOT reduced by resolution
What disorder is primarily associated with increased NT?
Noonan’s (most common associated single-gene disorder)
What is the frequency of cystic hygromas?
1:285 pregnancies
What are the most common causes of cystic hygromas?
50% aneuploidy
(Down, Turner, Trisomy 18, or other)
50% euploidy
(cardiac anomaly, skeletal anomaly, fetal demise, normal at birth)
Absent or hypoplastic nasal bone can be seen as early as ____ weeks.
11
What is an absent/hypoplastic nasal bone?
no calcification below the skin of the nasal bridge on US (bone is less echogenic than overlying skin)
Which ethnic group(s) have absent/hypoplastic NTs as a powerful soft marker?
Caucasians
absent in 9-10% of euploid Afro/Afro-Caribbean, 2.5% Caucasian, 6-7% Asian fetuses
What is a nuchal fold?
measurement of skin fold in the neck region (distinct from the first trimester nuchal translucency)
What designates a nuchal fold as elevated?
greater than 6 mm
What is an increased nuchal fold primarily associated with?
Down Syndrome
What is an echogenic intracardiac focus (EIF)?
spot within the heart, most often L ventricle, that is brighter than bone
What is an EIF most commonly associated with?
mostly in normal fetuses (3-8%) especially in euploid Asian fetuses
weakly associated with Down Syndrome (LR 1-2)
What is a choroid plexus cyst?
bil or unil cyst in choroid plexus region of the fetal brain that normally (~95%) resolves by 26 weeks gestation
What is most commonly associated with choroid plexus cysts?
trisomy 18
What is echogenic bowel?
bowel has brightness equal to or greater than that of surrounding fetal bone
Provide examples of possible non-genetic causes of echogenic bowel.
intra-amniotic bleeding –> fetus swallowed blood (ask if mom had bleeding)
infection (CMV, toxoplasmosis)
GI pathology (obstruction, atresia)-cannot be ruled out until birth
third trimester IUGR
Provide examples of possible genetic causes of echogenic bowel.
Down Syndrome
Other chromosome disorders
Cystic Fibrosis (due to meconium ileus causing bowel obstruction)
Always offer _____ and _____ as part of diagnostic work-up.
karyotype
microarray
What are the questions to ask yourself during the pre-counseling assessment?
Does the anomaly appear isolated?
Are there abnormalities present in more than one organ system?
Is there one main syndromic association or multiple possible differentials?
What other key findings to make diagnosis cannot be visualized on US?
List the CNS anomalies visible on US.
Ventriculomegaly
Holoprosencephaly
What is Ventriculomegaly?
dilation of the lateral cerebral ventricles of the brain resulting in increased CSF (unilateral or bilateral)
What causes ventriculomegaly?
chromosome abnormalities (3-15% if isolated)
Genetic syndromes
fetal infection (CMV, toxoplasma most common)
other brain malformations or spina bifida
What is L1 syndrome?
hydrocephalus with aqueductal stenosis
also associated with corpus callosum abnormalities
X-Linked
the most common genetic couse of congenital hydrocephalus (1/30,000)
What is holoprosencephaly?
incomplete or absent division of the forebrain into distinct lateral cerebral hemispheres
What are physical characteristics of holoprosencephaly?
midline facial malformations in most (eg. cyclopia, hypotelorism, single nostril, midline clefting, single central incisor, flat nose, mild midface hypoplasia)
Describe the possible causes of holoprosencephaly.
sporadic (6%) chromosomal (30%)- typically trisomy 13 single- gene syndromes (18-25%) non-syndromic AD forms maternal diabetes (1%)
List the craniofacial abnormalities visible on US.
cleft lip with or w/o palate
What conditions are cleft lip/palate associated with?
aneuploidy (trisomy 13, trisomy 18, chromosome 18 deletions, 4p deletions)
teratogens- EtOH, maternal PKU, hyperthermia, anticonvulsants
amniotic bands
over 300 genetic syndromes (most often isolated)
What is the incidence of cleft lip and/or palate?
1/1000 (M>F)
What is the incidence of isolated cleft palate?
1/2500 (M1:F2)
What are syndromic causes of cleft lip?
Van der Woude syndrome
Holoprosencephaly
DiGeorge (22q11.2 deletion)
Name the two types of abdominal wall defects.
omphalocele and gastroschisis
When is it abnormal to see midgut herniation of abdominal contents?
after 12 weeks gestational age
What conditions are associated with omphaloceles?
chromosomal (30-40%) genetic syndromes increased risk for IUGR and IUFD polyhydramnios other anomalies (50-75%) Increased MS-AFP
What US finding would change the risk of anomalies when an omphalocele is present?
herniated (giant) liver reduces risk for aneuploidy
What syndrome is most commonly associated with omphaloceles?
Beckwith-Wiedemann (BWS)
What is Beckwith-Wiedemann Syndrome?
overgrowth syndrome and imprinting disorder of region of 11p15 resulting in macrosomia, macroglossia, ear pits, visceromegaly, enlarged placenta, neonatal hypoglycemia
What factors are thought to be associated with gastroschisis?
young maternal age (<20 years)
cigarette smoking and drug abuse
What are other risk associated with gastroschisis found on US?
increased risk for IUGR, prematurity, and IUFD
low risk for aneuploidy
lower risk for other anomalies and syndromes
typically isolated
increased MS-AFP
What is congenital diaphragmatic hernia?
weakened or incompletely developed diaphragm resulting in abdominal contents enter thorax, impeding lung and heart development
85% found on the L side
What genetic etiologies are highly associated with diaphragmatic hernia?
karyotype abnormalities (10-35%)- trisomy 18 most common copy number variabts on array (3-13%) >20 monogenic disorders (eg. Cornelia de Lang)
List the genetic causes most greatly associated with the following congenital heart defects: TOF/Conotruncal arch abnormalities coarctation of aora supravalvular aortic stenosis pulmonary stenosis AV canal defect Ebstein anomaly heart block
22q11.2 deletion Turner Williams Noonan Down Lithium Maternal Lupus
What are rhabdomyomas?
most common cardiac tumor diagnosed in utero (normally not until the third trimester)
most regress after birth and don’t cause long-term cardiac complications (can rarely progress in growth resulting in cardiac output obstruction and a need for surgical resection
What kinds of testing should be offered to a pt whose fetus has rhabdomyoma(s) on US?
amnio for molecular diagnosis
microarray adn TSC1, TSC2 sequencing and deletion/duplication analysis
What teratogens are associated with ambiguous genitalia/disorders of sexual development?
progesterone, androgens, maternal androgen overproduction
What genetic etiologies are normally associated with ambiguous genitalia/disorders of sexual development?
predominately classic 21-OH deficiency CAH in females
low diagnostic yield in males
What is ambiguous genitalia?
undifferentiated external genitalia, or discordance between genetic sex and anatomic sex
What conditions are associated with ambiguous genitalia?
campomelic dysplasia
Smith-Lemli-Opitz
What is recommended to help distinguish between the AR and AD types of Polycystic Kidney Disease?
renal US and thorough family history
Describe the defining features of AR polycystic kidney disease.
bil massively enlarged echogenic kidneys (>4 SD above the mean) may or may not have visible cysts oligo-or anhydramnios non-visualized bladder Potter sequence
Describe the defining features of AD polycystic kidney disease.
moderately enlarged, echogenic kidneys (1.5-2 SD above the mean)
may or may not have visible cysts
expect normal AFV
What is radial hypoplasia/aplasia?
spectrum of upper extremity anomalies involving partial or complete absence of the radius bone
What is associated with US findings of hypoplasia/aplasia?
vascular accident/abnormal blood vessel development
chromosomal (trisomy 18, 13, mosaic trisomy 21)
medications (valproic acid, thalidomide, methotrexate)
Mendelian disorders
List the radial ray syndromes.
Fanconi anemia Cornelia de Lange Hold Oram (Heart and Hand) VACTERL TAR (thrombocytopenia absent radius) Roberts syndrome
What is Fanconi anemia?
absent, hypoplastic, supernumerary thumbs
How is Fanconi anemia diagnosed?
chromosomal breakage studies on cultured amniocytes
Describe the inheritance of achondroplasia.
AD
80% de novo
99% caused by two recurrent mutations in FGFR3
associated with advanced paternal age
What is Thanatophoric Dysplasia?
most common lethal skeletal dysplasia
caused by recurrent FGFR3 mutation
characterized by bowed femurs, “telephone receivers” in type I
colverleaf skull with straight femur in type II
What is a clubfoot?
positional abnormality of the foot where it is adducted and fixed
occuring most commonly in males (2:1)
44% bilateral (R more common if unilateral)
What conditions are associated with clubfoot?
> 200 chromosomal and genetic syndromes (chromosomal in 3-11%)
uterine environment decreased amniotic fluid, fibroids, uterine anomaly)
amniocentesis at <15 weeks (increases risk)
secondary to CNS anomaly or NTD (can be)
List the possible etiologies of Intrauterine Growth Restriction.
chromosomal (trisomy 18, 13, triploidy, UPD7 or 14, microdeletion/duplications)
genetic syndromes (numerous)
placental insufficiency
fetal infections (CMV, toxoplasma)
maternal factors (constitutional, renal disease, HTN, vascular)
small for gestational age
_____ is most likely when there are multiple anomalies, and ______ is normally associated with diffuse, multi-system anomalies.
syndromic
chromosomal
Describe the most likely etiologies in the setting of a negative family history.
multifactorial (most common for isolated birth defects but must exclude other etiologies before indicating this)
chromosomal (low risk)
single gene disorders (de novo AD mutations, AR disorders, x-linked disorders in the context of small amounts of males in the family)
