18.05.13 Summary of ultrasound findings and chromsome abnormalities Flashcards
What are the three major groups of foetal abnormality?
- Neural tube defects
2) Chromosome abnormalities
3) Congenital Heart Defects
What are the aims of first trimester ultrasound examination? When can this be performed?
11+2/40 - 14+1/40
1) Check the viability of the pregnancy
2) dating
3) Identified multiple regnancies
4) Placental localization
5) Detecting foetal anomalies
What is the single most powerful marker available today for differentiating Down syndrome pregnancies from euploid pregnancies?
First timerster measurement of the foetal nuchal translucency space (NT); the subcutaneous collection of fluid under the skin of the foetal neck. >3.5mm deemed significant.
Allows detection of 75-80% of fetuses with aberrant karyotype.
What are the possible causes of a raised NT? How can a raised NT progress?
1) Cardiac failure due to secondary or structural malformation
2) Abnormal or delayed development of the lymphatic system
Can progress into nuchal oedema, cystic hygroma or foetal hydrops in the second trimested.
May regress
A raised NT is associated with an increased risk of chromosomal disorders. Which are the most common?
T21, T18, T13 and Turner syndrome (respectively).
Tripoloidy - less common
Give some examples of structural malformations can be detected in the first trimester ultrasound scan?
Absent nasal bone Regurgitant flow across tricuspid valve (Doppler evaluation of foetal ductus venosus) Holoprosencephaly Omphalocele Megacystis Limb abnormalities
What can a Doppler evaluation of the foetal ductus venosus show? What association does this have with chromosome aneuploidy?
Doppler evaluation of foetal ductus venosus - regurgitant flow across the tricuspid valve is associated with aneuploidy and foetal cardiac malformations (75% of T21 vs 7% chromosomally normal).
What can be detected during nasal bone sonography? What association does this have with chromosome abnormalities?
Nasal bone presence/absence - not visible in 60-70% of T21, 55% of T18 and 34% T13 (may not be seen in 2% of abnormal)
What is holoprosencephaly? What is its association with chromosome abnormalities?
Physiological failure of the brain to divide into lobes or hemispheres. 30% of cases will have a chromosome abnormality. T13 T18 7q36 SSH gene at 7q36 responsible for HPE
What is omphalocele? What is its association with chromosome aneuploidy?
Herniation of the foetal abdominal contents due to the physiological failure of the abdomen to close around the umbilical cord.
60% from 12 weeks scan will have a chromosome abnormality (35% in mid-gestation due to high rate of IUD).
T13
T18
Beckwith-Wiedemann
What is megacystis? What chromosome abnormalities can it be associated with?
Enlarged foetal bladder due to ureteric obstruction.
T13
T18
Give some examples of limb abnormalities that can be detected on the first trimester scan and the chromosomal abnormalities they are associated with.
Relative shortening of the long bones: T21, T18, triploidy and Turner syndrome
Syndactyly is associated with triploidy
Clinodactyly and sandal gap - T2
Polydactyly - T13
Overlapping fingers, rocker-bottom feet, talipes - T18
When can a mid-trimester foetal anomaly scan be performed?
18+0/40 - 20+6/40
Give five possible scan findings in a 2nd trimester T21 pregnancy?
25% of second trimester T21 pregnancies will have major congenital anomalies detectable by ultrasound.
1) Brachycephaly
2) Nail hypoplasia
3) Nuchael oedema
4) Cardiac defects (mainly AVSDs, ToF)
5) Intracardiac echogenic foci
6) Duodenal atresia (30% with have T21)
7) Echogenic bowel
8) Sandal gap
9) Clinodactyly of the fifth finger
10) Transverse palmar crease
11) Hydrops
12) IUGR
13) Renal anomalies
14) Syndactyly
Give five possible scan findings in a 2nd trimester T18 pregnancy?
1) Choroid plexus cyst
2) Absent corpus callosum
3) Enlarged cisterna magna
4) Facial cleft
5) Micrognathia
6) Nuchael oedema
7) Heart defects e.g. VSD
8) Horeshoe kidney and other renal defects
9) Diaphragmatic hernia
10) Oesophageal atresia
11) Exomphalos
12) Single umbilical artery
13) Echogenic bowel
14) IUGR
15) Overlapping fingers, talipes/rocker-bottom feet
16) Substantially decreased placental volume
17) Neural tube defects
18) Radial hypoplasia
Give five possible scan findings in a 2nd trimester T13 pregnancy?
1) Holoprosencephaly +/- cleft lip/palate
2) IUGR
3) Microcephlay
4) Cardiac (AVD or VSD)
5) Renal abnormalities and often large and echogenic kidneys
6) Exomphalos
7) Post-axial polydactyly
What kind of triploidy may continue past 20 weeks? What are some indications of this type of pregnancy on the 2nd trimester scan?
Diandy - rarely past 20 weeks Digyny - may persist into the third trimester. Placenta is thin and the foetus shows: 1) severe asymmetrical growth restriction 2) Mild ventriculomegaly 3) Micrognathia 4) Cardiac abnormalities 5) Myelomenigocoele 6) Syndactly 7) Hitch-hiker toe deformity 8) Holoprosencephaly 9) Dandy-Walker malformation
What are the common indications of a Turner syndrome pregnancy on 2nd trimester scan?
Large nuchal cystic hygroma.
75% of foetus with cystic hygroma will have a chromosome abnormality and 95% of these is Turner syndrome.
Generalised oedema Mild pleural effusions and ascites Cardiac abnormalities Horseshoe kidney Hydrops IUGR
What features may indicated mosaic trisomy 2 on a 2nd trimester scan?
1) absent gall bladder
2) Talipes
3) Renal cysts
What features may indicated mosaic trisomy 7 on a 2nd trimester scan?
1) Low set ears
2) Talipes/rocker-bottom feet
3) Clitoromegaly
4) Renal agenesis
What features may indicated mosaic trisomy 8 on a 2nd trimester scan?
1) Skeletal anomalies
2) Cardiac defects
3) Renal abnormalities
What features may indicated mosaic trisomy 9 on a 2nd trimester scan?
1) IUGR
2) Microphthalmia
3) Cardiac defects
4) Vermis hypoplasia
5) Enlarged renal cysts
What chromosome abnormality is associated with Pallister-Killian syndrome. What are the possible prenatal indications of this syndrome?
Mosaic tetrasomy 12p
1) Congenital diaphragmatic hernia
2) Short limbs
3) Abnormal hands and feet
What chromosome abnormality is associated with Wolf-Hirschhorn syndrome. What are the possible prenatal indications of this syndrome?
4p16. 3 deletion
1) IUGR
2) Microcephaly
3) Cleft lip
4) Heart defects
What chromosome abnormality is associated with Cri-du-chat syndrome. What are the possible prenatal indications of this syndrome?
5p15 deletion
1) CHD
2) Cleft lip and palate
What chromosome abnormality is associated with Miller-Dieker syndrome. What are the possible prenatal indications of this syndrome?
17p13.3 deletion
Lissencephaly
What chromosome abnormality is associated with Williams syndrome. What are the possible prenatal indications of this syndrome?
7q11. 23 deletion
1) IUGR
2) Nasal bone hypoplasia
3) Cardiac defects
What chromosome abnormality is associated with Di-George syndrome. What are the possible prenatal indications of this syndrome?
22q11. 2 deletion
1) Cardiac defects (particularly outflow tract defects, ToF)2) Renal abnormalities
3) IUGR
4) Polyhydramnios
5) Cleft lip and palate
6) Thymic hypoplasia
What genetic/chromsome abnormality is associated with Roberts syndrome. What are the possible prenatal indications of this syndrome?
ESCO2 gene can be tested where mutations are known. PCS on solid stain chromosome preps.
1) Severe limb shortening (upper limbs more affected)
2) Oligodactyly
3) Thumb aplasia
4) Cleft lip
5) Cystic kidneys.
What are some prenatal SCAN indications of UPD?
UPD7mat (SRS) asymmetrical growth restriction
UPD11pat (BWS) Overgrowth in association with omphalocele
UPD14mat - small thorax and polyhydramnios
What are the antentally detectable songraphic features of achondroplasia?
May not be detectable until the 3rd trimester
1) Short femur length measurement <5th centil
2) Trident hand - 2,3,4 fingers similar in length
3) Frontal bossing
