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Ultrasound Detection of the Chromosomal Abnormalities DR. NABEEL BONDAGJI FRCSC, FACOG Associate Prof. Consultant King Abdulaziz University Hospital Consultant Perinatologist King Faisal Specialist Hospital & Research Center - Jeddah
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Introduction Spontaneous abortions 50% 50% trisomy 25% monosomy 10-15% mosaic Others Stillbirths/neonatal deaths 6-11% Live births 0.56% 1/3 autosomal, 1/3 sex xm, 1/3 other In AMA patients undergoing amnio (2.26%) 64% trisomy, 17% sex xm, 19% other
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Current Screening Methods Advanced maternal age (AMA) ( 35 yrs) Maternal serum screening (MSS, triple test. Free BHCG & Alpha HCG and the PAPPA Family/personal history Ultrasound
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Diagnostic Methods 1. Amniocentesis Early Mid trimester 2. CVS 3. Cordocentesis 4. Fetal cells in the maternal circulation (experimental)
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Frequency of aneuploidies vs the number of anomalies Number of anomalies PERCENTAGE
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How Good is Ultrasound in Detecting Anomalies? Chity et al BMJ 1991 84322 nd trimester U/S 74% detection rate 87% severe anomalies Lucle et al BMJ 1992 85232 nd trimester U/S 87.5% detection 92.9% severe anomalies
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Accuracy of Ultrasound in Detection of Chromosomal Abnormalities Variables: Trisomy 1885-90%detection Trisomy 1385%detection Trisomy 2160%detection
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Specific Chromosomal Abnormalities 1. Triploidy 2. Trisomy13 3. Trisomy18 4. Trisomy21 5. Monosomy 45 x 0 Turner S.
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Trisomy 21 (Down Syndrome) ULTRASOUND ABNORMALITIES ASSOCIATED WITH DOWN SYNDROME 1. Nuchal translucency (nuchal edema) 40% of D.S. at 13 weeks 2. Thickened nucal fold 2 nd trimester 5-33% down 3. Ventriculomegally 4. Flattened facial profile 1:660 M:F1:1
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5. Isolated pleural effusion 6. Congenital heart disease 50% of D.S. comment is endocardial cushion effect 7. Duodenal atresia 25% of Down (double bubble) 8.Ecogenic focus in the heart
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9. Dilatation of the renal pelvis 10. Short femure : 0.91 of the expected femur length increase the rate of detection sensitivity 68%, specificity 98%. (Benacerraf)
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11. Short humorous 12. Short fifth finger 13. The big toe separated from the rest (sandal sign) 14. Echogenic bowels 12.5% of Down babies +ve 5% folds increase in Down Syndrome
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Prognosis CHD – shorten the life span GI Defect I.Q. is limited 25-50 Hypotonia
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First Trimester Nuchal Edema Nicolaides et al (BMJ ’92) 827 women undergoing 1 st TM karyotyping Nuchal edema: Subcutaneous translucency between skin and overlying tissue 3mm 51/827 (6%) cases had nuchal edema (3mm- 8mm) Abnormal chromosomes 18/51 (35%) mainly T21) Only 10/776 (1%) with no nuchal edema were chromosomally abnormal
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First TM Nuchal Edema Nuchal edema 3mm assoc with 10x risk for Xm abn Mainly trisomies (T21) as in 2 nd TM NF Sensitivity for T21 is approx 75% Incidence of nuchal edema in normal is approx 4%
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Pondya and Nicalaides Ultrasound in OB/GYN 1995 1015 Amnio for Increasing Nuchal Translucency Thickness 3 mm3 times higher than expected on basis of age 4 mm18 times 5 mm28 times 6 mm36 times
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Echogenic Bowel Nyberg et al (Obstet Gynecol’91) 7% of T21 fetuses had echogenic bowel (2 nd TM) Scioscia et al (Am J ’92) 6/19 (32%) of fetuses with echogenic bowel had Xm abn 5 T21, 1 T18 HOWEVER, 4/6 had other abnormalities Crane et al 1/30 (3.3%) cases with echogenic bowel had T18
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Fetal Cerebral Ventriculomegaly Filly et al (’91): Posterior horns of lateral ventricles GA independent (15-40 weeks) Normal < 10mm (mean 6-7 mm) Borderline 10-12 mm (or 10-15 mm) Abnormal 15mm Should be routinely measured at 18 week scan
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Isolated Mild Ventriculomegaly Summary of published cases (Achiron ’89-92) Incidence of fetal trisomy: 11/92 (12%) Spontaneous resolution in utero: 17 (18%)
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Benacerraf and Group Scoring System Nucal Fold =2 Major structural defect =2 e.g. endocardial cushion, ompholocele, etc. Short femur & S = 1 Echogenic focus = 1 Pylactasis = 1 Echogenic Bowel = 1 Assoc with 2 or more will detect 81% of Down fetuses
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TRISOMY 18 Incidence:1:3000 1:5000 M:F 1:3
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Ultrasound Abnormalities Limb abnormalities clenched hand and overlapping of the fingers Rocker-Bottom feet Micrognethia Congenital Heart Disease in 80% – VSD comment – TGV Fallot Tetralogy
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choroid plexus cyst 25% 2-9% of CPC associated with trisomy 18 Omphalocele 25% Enlarged cisterna magna 15% Echogenic chordae tendaneai 35% Diaphragmatic hernia 30% associated of aneuploidy and the majority are 18%
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The Posterior Fossa Includes cerebellum and cisterna magna Measures 1-10 mm (>10mm abnormal) Abnormalities: Dandy Walker malformation Dandy Walker variant Large cisterna magna (“Mega-cisterna magna”)
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Large Cisterna Magna Cisterna magna 10mm Vermis intact, hydrocephalus usually absent Nyberg et al (Obstet Gynecol\91) 33 fetuses cisterna magna > 10mm Assoc anomalies 30/33 (90%) Chromosome abnormalities 8/33 (55%) T18 (12), T13 (3), other (3) Correlated with absence of ventriculomegaly and presence of other anomalies
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Prognosis: lethal poor prognosis 70% antenatal still birth 85% die in 1 st year all senses profound mental retardation - failure to thrive - hearing defect - visual difficulties - seizures
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Ultrasound Abnormalities Associated with Trisomy 13 Single umbilical artery Midline cleft, Cyclops(45%) Microcephaly(12%) Incidence 1:50001:10000 Births
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Holoprosencephaly(40%) polydactly and syndactaly Scalp defect A S D, VSD and hypoplastic left heart .agenesis of the corpus collosum
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Holoprosencephaly Failure of cleavage of pros encephalon Alobar, semilobar and lobar Assoc with facial defects (cyclope, proboscis, clefts) Incidence of chromosome abnormalities: 40-60% Usually Trisomy 13 Also trisomy 18, triploidy, 5p+, 13 q-,18p-.
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Agenesis of Corpus Callosum Associated with variety of Xm abnormalities Trisomy 13, 18, 8, triploidy and translocations Bertino et al (J U/S Med’87) 1/8 (14%) with fetus with agenesis CC: Trisomy 8
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Prognosis Lethal Poor Prognosis 50% dies 1 st two months 90% dies 1 st year Survivors will develop profound mental retardation
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Ultrasound Abnormalities Associated with Triploidy Severe IUGR (early onset) Oligohydramnios Molar degeneration of the placenta Holoprosencephaly & agenesis CC Prognosis:lethal antenatally mosaicM.R.
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Turner Syndrome Ultrasound Abnormalities Cystic hygroma 90% of Turner CHD aortic coarctation Renal agenesis & pelvic kidney and horse shoe kidney Hydrops fetalis 1:50001:1000
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Prognosis: With hydrops mortality approaches 100% survivor: Degree of CHD Hearing defect 50% Absence of 2 nd sexual character and infertility Skeletal growth retardation Normal intelligence
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Nuchal Cystic Hygroma Azar et al (Fetal Diag Ther ’91) Abnormal chromosomes: 75% Turner’s syndrome (45 x0): 94% Assoc CHD 48%, renal 20%, abn biometry 90% Normal chromosomes: 25% Associated abnormalities: 75% Live born healthy: 2-3%
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Thank You
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