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20 Cards in this Set
- Front
- Back
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Indications for prenatal diagnosis
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-previous child with autosomal trisomy
-parent carrier of chromosomal rearrangement -previous child, patient or spouse with a neural tube defect -abnormal second trimester maternal screen -abnormal 1st trimester screen -pregnancy at risk for diagnosable genetic disorder -ultra sound findings |
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Types of Diagnostic Tests in Prenatal Diagnosis
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-CVS
-Amnio -PUBS-percutaneous umblical sampling -PGD |
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Amnioocentesis: when? Accuracy
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- start at 15 weeks, traditional time 16-18 weeks
-not usually performed after 22 weeks -accuracy >99% |
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What are the risks of amnio?
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Fetal injury: rare
Maternal infection: rare Abruption: non-existent Spontaneous loss: 1 in 500 to 1 in 1000 |
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Detection of NTD's with Amnio
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-99.5% detection by amnio measuring AFAFP and presence/absence of acetylcholinesterase
-compared with 80-95% detection by ultrasound alone |
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CVS
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-10-12 weeks days for transcervival
-transabdominal approach at any age -approximatley 99% accurate -risk of complications similar for amnio |
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CVS Indications
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SAME FOR AMNIO EXCEPT:
1) inaccurate for NTD (cannot measure AFP) 2) too late for abnormal second trimester screen |
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CVS Mosacism: how often? how often true mosaics?
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-1-2% of cases
-20% are true mosaics -80% confined placental mosaicism -consider UPD testing |
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Banana and Lemon Sign
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Indication of neural tube defects
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Duodenal Atresia
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30% incidence of downs syndrome
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Ventral Wall Defects
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Omphalocele: much higher risk of anomalie (60%)
Gastrochisis: (24%) |
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Common U/S findings in Trisomy 21 (soft markers vs true birth defects)
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-increased nuchal thickness
-echogenic bowel -echogenic intracardiac focus -short humerus -short femur -dilated renal pelvis -cardiac defect TRUE Birth Defects -Cystic hygroma with or without hydrops -cerebral ventricular dilation -duodenal atresia |
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Associated with Echogenic Bowel
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Down sx
cytomegalovirus intra-amniotic bleed placental insufficiency |
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Echogenic Intracardia Focus
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Slight increase risk for down syndrome
common in asian descent and not useful |
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Heart Defects and Down Syndrome
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-50% have congenital heart defect
-AVSD most common (59%) -others seen |
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Common U/S Findings in Trisomy 18
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Choroid plexus cysts (minor marker, common in general)
Clenched hands Rocker bottom feet delayed growth heart defects omphalocele |
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Choroid Plexus Cyst
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-Slight association with trisomy 18
-all disappear by 24 weeks gestation -not associated with other CNS abnormalities |
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Trisomy 13
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-Cleft palate
-polydactyly delayed growth heart defects holoprosenscephaly |
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PGD: Two methods
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1. Polar body (opposite of diagnosis)
2. PGD itself |
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Shortcomings of PGD
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1. Failure of PCR
2. Allele Dropout 3. Sperm Contamination 4. Cost 5. Low pregnancy rates with IVF 6. Limited availability |
