Antenatal Ultrasound as a diagnostic modality for congenital anomalies in fetus (from fetal point of view)

1. ANTENATAL ULTRASOUND AS A
DIAGNOSTIC MODALITY FOR
CONGENITAL ANOMALIES
Presented by: Dr. Prashant Srivastava
MD (Pediatrics)

2. ULTRASOUND
• Important role in the care of pregnant women
• Safe, non-invasive, non-ionising radiation,
accurate and cost effective investigation for fetus
• Based on the principle of SONAR
• High frequency sound waves generated from a
transducer penetrate through tissues of different
densities and reflected energy to the transducer
is amplified and displayed on screen

3. Uses of Antenatal Ultrasound
1. Establish the presence of a living embryo/fetus
2. Age of pregnancy
3. Diagnosing congenital abnormalities in fetus
4. Position of fetus and placenta
5. Amount of amniotic fluid
6. Assess fetal well-being
It’s disadvantage is being observer dependency.

4. Antenatal USG in 1st Trimester
• Following fetal details are noted-
a. Recording the presence or absence of fetal life
b. Identification and documenting the fetal number
c. Gestational age
d. Major structural abnormalities (e.g anencephaly)

5. Antenatal USG in 2nd and 3rd Trimester
• Fetal viability, number.
• Amount of amniotic fluid
• Fetal age and growth estimation
Head Circumference and shape of skull
Femur Length
Abdominal Circumference
• Congenital abnormalities

6. Evaluation of Fetal Anatomic
Structures
• Cerebellum and Cerebral ventricles
• Spine
• Stomach-bowel, abdominal wall at the area
of the umbilical cord insertion
• Bladder and kidney
• All 4 limbs
• Four chamber view of the heart

7. Fetal Age Estimation in 1st Trimester
• Identification of Gestational sac- Correlation of fetal
age with LMP
• Fetal Age Estimation in 2nd & 3rd Trimester
i. Bi-parietal diameter measurement- Around 9
weeks until end of pregnancy
ii. Head circumference measurement-Gestational age
prediction when abnormal skull shape, measured
on same plane as bi-parietal diameter
iii. Abdominal Circumference measurement- Less
accurate for estimating gestational age
iv. Femur length- Fetal age assessment

8. Nuchal Translucency
• Evaluation of subcutaneous fluid behind the fetal
head, neck and torso between 11-13+6 weeks
gestation.
• Single most effective screening test for fetal
aneuploidy
• Increased nuchal thickness (>95th centile) is
associated with fetal chromosomal defects
• Fetuses with increased NT with normal karyotype
are at increased risk for structural anomalies
• Fetuses with increased NT must undergo detailed
2nd trimester scan and fetal Echo

9. Second Trimester USG
• Best performed at 18-20 weeks
• Detailed anatomic survey of fetus
• Approx. one-third of fetuses affected with trisomy
21 have a major or minor structural variation
identifiable on USG.
• Other detectable abnormalities- holoprosencephaly,
facial cleft, cystic hygroma, diaphragmatic hernia,
posterior fossa cyst, major heart defects, duodenal
atresia, hyperechoic bowel, omphalocele, early FGR,
talipes

10. • Detecting structural anomalies in 2nd trimester
helps in identifying abnormalities a/w severe
morbidity or incompatible with life and parents can
take a informed decision for MTP.(e.g anencehaly,
meningomyelocele)
• Few anomalies like urinary tract abnormalities,
microcephaly, skeletal dysplasia are progressive
and late in onset and may not be detectable at 18-
20 weeks USG.

11. Soft Markers (Not abnormalities in
itself but indicate risk of congenital
abnormality)
Biometric Parameters Morphologic signs
 Short length of femur
 Short length of humerus
 Pyelectasis
 Increased nuchal fold
 Ventriculomegaly
 Hypoplastic or absent nasal
bone
 Early FGR
 Choroid plexus cyst
 Echogenic bowel
 Echogenic intracardiac foci
 Aberrant right subclavian
artery

12. COMMON FETAL
STRUCTURAL
ABNORMALITIES

13. Anterior Abdominal Wall Defects
• Gastroschisis, omphalocele, limb body wall
complex
• Omphalocele, if a/w other congenital
abnormalities and chromosomal aneuploidy, has
high risk of antenatal mortality.
• Isolated omphalocele has good post surgical
prognosis in neonatal period.
• Gastroschisis is not a/w other congenital
abnormalities, but complex postnatal period
depending on extent of organ involvement.

14. Omphalocele & Gastroschisis

15. • Limb body wall complex and pentalogy of
Cantrell are universally lethal during antenatal
life.
• Antenatal detection of these abdominal wall
defects helps in-
Planning for amniocentesis to detect
chromosomal anomalies in omphalocele a/w
other congenital anomalies
Delivery in a tertiary care centre with pediatric
surgery backup.

16. CNS Abnormalities
• Common neural tube defects- Anencephaly,
encephalocele, hydrocephalus with or without
spina bifida
• Large open neural tube defects, especially at
upper vertebral levels (cervical, thoracic) have
poor prognosis
• Smaller lesions like meningocele without cord
tethering may be detected later in pregnancy or
after birth due to small size and lack of classical
signs of tentorial herniation or neurological
deficits and have a good prognosis with surgery

17. Anencephaly & Encephalocele

18. Congenital Cardiac Defects
• Complex cardiac defects like hypoplastic left or
right ventricle, large atrioventricular septal
defects, valvular atresia/severe valvular stenosis-
worse prognosis due to anomaly itself or a/w
other congenital anomalies or chromosomal
aneuploidies.
• Cardiac defects which are relatively non-lethal or
have good surgical prognosis- Isolated septal
defects, isolated TGA, Fallot’s tetrology with
good size pulmonary artery, TAPVCs, milder
varieties of coarctation of aorta

19. Further antenatal monitoring is necessary for
Detection of worsening of cardiac function,
signs of heart failure or development of hydrops
Deciding the timing of delivery
Deciding the level of hospital care for delivery
with availabilty of NICU, cardiac surgeon and
cardiac anesthetist

20. Congenital Lung Malformation
• Fetal thoracic masses- CPAM,BPS
• If a/w hydrops, these are fatal.
• Congenital pulmonary airway malformation volume
ratio (CVR)- Helps in determining the risk of
development of hydrops.
• CVR- Volume of the mass normalized for gestational
age. CVR> 1.6 predicts increased risk of developing
hydrops.
• In post-natal period, early thoracoscopic surgery is
required if available & in competent hands and if
neonate is symptomatic

21. Congenital Diaphragmatic Hernia
• If diagnosed before 26 weeks, a/w liver
herniation and a low lung to head circumference
ratio (LHR<1)- Poor prognosis after birth
• LHR – Ratio of opposite normal lung area to
head circumference
• Antenatal management includes antenatal
monitoring for development of hydrops, cardiac
dysfunction, delivery at a tertiary care centre,
following standard protocols after birth after
initial stabilization and then, surgical
management

23. Fetal Genitourinary Anomalies
• Bilateral renal agenesis is incompatible with life
• Common- urinary tract dilation disorders like
PUJ obstruction, VUR, posterior urethral valves,
urethral atresia (complete/partial)
• All these present with varying degree of
hydronephrosis, depending on severity of
obstruction
• All urinary tract dilatation abnormalities need
antenatal USG monitoring at monthly intervals
for worsening, oligohydroamnios, cortical
thickness, echogenicity and fetal maturity

24. SFU Grading of Ante-natal HDN
Classification Renal pelvic anteroposterior
diameter (APD)
Second trimester Third trimester
Mild 4-6 mm 7-9 mm
Moderate 7-10 mm 10-15 mm
Severe >10 mm >15 mm

25. Gastrointestinal Anomalies
• USG findings- hyperechogenic bowel,
polyhdramnios
• Common anomalies- Esophageal atresia with or
without TEF, duodenal atresia, intestinal atresia
• Higher the obstruction, earlier the presentation
in antenatal period by polyhydramnios and
proximally dilated loops.
• Delivery at tertiary care centre and early surgical
intervention reduces morbidity and better
prognosis

26. Ano-rectal Malformation
• USG – Less sensitive and specific to detect ARM
• Frequently a/w sacral agenesis and lower limb
hypoplasia as part of caudal regression
syndrome
• VACTERL- Association between vertebral, anal,
cardiovascular, tracheo-esophageal, renal and
limb malformation

27. • USG findings suggestive of ARM
i. Absence of the circular rim of hypo-
echogenicity in the perineum- Imperforate anus
ii. Enterolithiasis and dilated fetal colon – Indirect
evidence of ARM
• Suspected ARM need fetal MRI in 3rd trimester

28. GUT ROTATIONAL ANOMALIES
• Antenatal USG shows polyhydramnios, distended
stomach, collapsed bowel loops, ascites
• ‘Single bubble’ sign due to distended stomach point
towards rotational anomalies
• Whirlpool sign- Abnormal relationship b/w SMA &
SMV
• Barber pole sign- Duodenal atresia
• Some anomalies like fetal volvulus can be life
threatening
• If twisting of bowel loops cause twisting of
mesenteric artery, it lead to bowel necrosis

29. Biliary System Anomalies
• USG is less specific for detecting
abnormalities of biliary system antenatally
• Abnormalities that might be detected-
Agenesis, left-sided, septated or bilobed gall-
bladder
• GB with an irregular wall a/w a cyst of the
extrahepatic biliary tract should raise
suspicion of CBA.

30. Antenatal diagnosis of PUV
• Bladder wall thickening >3 mm is considered
abnormal.
• Amniotic fluid volume and appearance of fetal
renal cortex- predictors of post-natal renal
function.
• Presence of bilateral hydroureteronephrosis with
or without oligohydramnios
• Dilated posterior urethra with a thickened fetal
bladder- characteristic appearance of keyhole

31. • Megacystitis- Large Fetal bladder
measuring>10 mm in sagittal plane, non-
specific indicator of PUV, uretral atresia or
stenosis, prune belly syndrome, megacystis-
microcolon-intestinal hypoperistalsis
syndrome and cloacal anomalies.

32. DISORDERS OF AMNIOTIC
FLUID AND THEIR RELATION
WITH FETAL CONGENITAL
ANOMALIES

33. Oligohydramnios
• Amniotic fluid <200 ml at term or amniotic fluid
volume <5th centile for gestational age
• AFI<5 cm at 28-40 weeks or single vertical pocket
<2 cm
• It can be due to-
Renal agenesis, urinary obstruction
Spontaneous rupture of membranes
IUGR, Intrauterine infection
Fetal chromosomal and structural anomalies
(potter’s syndrome)
Drugs: PG inhibitors, ACE inhibitors

35. Fetal complications due to
Oligohydramnios
• Abortion/Intrauterine fetal death
• Prematurity
• Deformities- CTEV, contractures, amputation
• Malpresentations
• Fetal distress
• MAS
• Low APGAR

36. Polyhdramnios
• Amniotic liquor >2000 ml
• AFI >25 cm or >95th centile for gestational age and a
large vertical pocket >8 cm
• Excessive production of liquor amnii can be due to
 Anencephaly, open spina bifida, transudation from
exposed meninges
 absence of fetal swallowing reflex,
esophageal/duodenal atresia/neonatal intestinal
atresia, facial clefts/neck masses,
 hydrops fetalis, cardiothoracic anomalies
 Aneuploidy, multiple pregnancy

38. CONCLUSION
• Antenatal USG is a good diagnostic technique for
detecting major congenital abnormalities in
babies.
• It helps in directing towards further diagnostic
evaluation like amniocentesis, CVS, fetal MRI,
genetic testing etc
• It helps in taking decision towards continuation
or termination of pregnancy
• It helps in choosing place of delivery and better
perinatal & postnatal management

39. THANK YOU