Features of chromosomal abnormalities in TIFFA scan
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Chromosomal Abnormalities on TIFFA Scan
TIFFA (Targeted Imaging for Fetal Anomalies) is a detailed mid-trimester anomaly scan performed between 18–22 weeks of gestation. It systematically evaluates fetal anatomy and is a key tool for detecting structural markers of chromosomal aneuploidies.
Hard Markers (Major Structural Anomalies — High Predictive Value)
These are significant structural defects strongly associated with chromosomal abnormalities:
Central Nervous System
| Finding | Associated Aneuploidy |
|---|---|
| Agenesis of corpus callosum | Trisomy 18, 13 |
| Holoprosencephaly | Trisomy 13, 18 |
| Neural tube defects (spina bifida, anencephaly) | Trisomy 18 |
| Mega cisterna magna / Dandy-Walker malformation | Trisomy 18, 13 |
| Ventriculomegaly (>10 mm) | Trisomy 21, 18 |
| Choroid plexus cysts (CPCs) | Trisomy 18 (bilateral CPCs) |
Cardiac
| Finding | Associated Aneuploidy |
|---|---|
| Ventricular septal defect (VSD) | Trisomy 21, 18, 13 |
| AV canal defect (AVSD) | Trisomy 21 (strongly) |
| Hypoplastic left heart | Trisomy 18 |
| Transposition of great arteries | Monosomy X (Turner) |
| Tetralogy of Fallot | Trisomy 21, 18 |
| Coarctation of aorta | Turner syndrome |
Facial
| Finding | Associated Aneuploidy |
|---|---|
| Cleft lip and/or palate | Trisomy 13 (midline), 18 |
| Hypotelorism / cyclopia | Trisomy 13 |
| Proboscis | Trisomy 13 |
| Micrognathia | Trisomy 18 |
Abdominal / GI
| Finding | Associated Aneuploidy |
|---|---|
| Omphalocele | Trisomy 18, 13 |
| Duodenal atresia ("double bubble") | Trisomy 21 |
| Esophageal atresia | Trisomy 18, 21 |
| Diaphragmatic hernia | Trisomy 18 |
Musculoskeletal / Extremities
| Finding | Associated Aneuploidy |
|---|---|
| Rockerbottom feet | Trisomy 18 |
| Overlapping fingers (clenched fist) | Trisomy 18 |
| Radial aplasia | Trisomy 18 |
| Polydactyly | Trisomy 13 |
| Talipes equinovarus (clubfoot) | Trisomy 18 |
| Short limbs / skeletal dysplasia | Various |
Renal / Urinary
| Finding | Associated Aneuploidy |
|---|---|
| Renal agenesis / Potter sequence | General chromosomal disorders |
| Horseshoe kidney | Turner syndrome (45X) |
| Echogenic kidneys | Trisomy 13 |
Soft Markers (Minor Ultrasound Features — Adjust Risk; Low Predictive Value Alone)
These are minor findings that increase the risk of aneuploidy when isolated but do not indicate anomaly by themselves:
| Soft Marker | Primary Association |
|---|---|
| Nuchal fold thickening (≥6 mm at 16–22 wks) | Trisomy 21 (strongest soft marker) |
| Short femur (< 5th centile) | Trisomy 21 |
| Short humerus | Trisomy 21 |
| Echogenic bowel | Trisomy 21, cystic fibrosis |
| Echogenic intracardiac focus (EIF) | Trisomy 21 (especially bilateral; moderate LR) |
| Mild renal pelvis dilatation / pyelectasis (AP ≥ 4 mm) | Trisomy 21 |
| Choroid plexus cysts (bilateral) | Trisomy 18 |
| Ventriculomegaly (mild, 10–12 mm) | Trisomy 21 |
| Single umbilical artery (2-vessel cord) | Trisomy 18 |
| Sandal gap (wide 1st–2nd toe space) | Trisomy 21 |
| Absent/hypoplastic nasal bone | Trisomy 21 |
| Clinodactyly (curved 5th finger) | Trisomy 21 |
Note: When two or more soft markers are present together, the likelihood ratio for trisomy 21 rises significantly, warranting invasive testing.
Chromosome-Specific Summary
Trisomy 21 (Down Syndrome)
- Nuchal fold thickening, duodenal atresia, AVSD, short femur/humerus, EIF, echogenic bowel, absent nasal bone, sandal gap, mild ventriculomegaly, clinodactyly, pyelectasis
Trisomy 18 (Edwards Syndrome)
- Clenched fists / overlapping fingers, rockerbottom feet, choroid plexus cysts, IUGR, omphalocele, cardiac defects, micrognathia, single umbilical artery, neural tube defects, polyhydramnios (due to swallowing difficulty)
Trisomy 13 (Patau Syndrome)
- Holoprosencephaly, cyclopia/hypotelorism, proboscis, cleft lip/palate (midline), polydactyly, IUGR, echogenic kidneys, cardiac defects, omphalocele
Turner Syndrome (45,X0)
- Cystic hygroma (most common), horseshoe kidney, coarctation of aorta, lymphedema, hydrops fetalis
Triploidy (69,XXX or 69,XXY)
- Severe early-onset IUGR, large placenta (with molar changes), oligohydramnios, mild ventriculomegaly, cardiac defects, 3-4 toe syndactyly
Clinical Approach
- Isolated soft marker → Reassess with prior risk (age, serum screen); usually no invasive testing needed if low background risk
- Multiple soft markers → Significantly elevated risk; offer genetic counseling and consider invasive testing (amniocentesis/CVS)
- Any hard marker (major structural anomaly) → High association with chromosomal abnormality; karyotyping / chromosomal microarray strongly recommended
- Combined with biochemical screening (NIPT, quad screen) → Risk stratification is most accurate when imaging and biochemical data are integrated
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