Term
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Definition
examination of asymptomatic individuals to determine if they are at high probability of developing certain genetic condition
Inexpensive and non invasive tests |
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Term
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Definition
| Determination of the presence of a disease |
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Term
| Indications for prenatal diagnosis |
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Definition
1. Maternal age - used to be indicator - now open to any age
2. Structural abnormality in parent
3. Previous child with chromosomal abnormality
4. Risk based on family history or based on results of screening
5. Sex determination (for X linked disorders)
6. Family history of NTD
7. Elevated AFP |
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Term
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Definition
15-18 weeks
Fetal cells sent for FISH and chromosome analysis
Supernatant sent for serum markers such as AFP |
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Term
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Definition
NTD
Fetal blood contamination
Fetal abnormalities
Placental abnormalities |
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Term
| Risk of fetal loss with amniocentesis |
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Definition
T&T: 1/1600 over baseline
Meta analysis: 0.6% increased risk
Commonly quoted: 1/300-1/500 |
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Term
| Complications of amniocentesis (excluding miscarriage) |
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Definition
Feto-maternal hemorrhage
Leakage of amniotic fluid
Infection
Respiratory distress
Increased risk of transmission of HepB and HIV |
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Term
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Definition
10-14 weeks
Not acceptable due to high risk |
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Term
| Chorionic villus sampling |
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Definition
10-12 weeks
Can be performed transcervical (more risky) or transabdominal (safer)
Cannot determine AFP
Sometimes there is mosaicism |
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Term
| Risk of fetal loss with CVS |
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Definition
T&T: 1/100 over baseline
Meta analysis: 2.4% increase over amnio = 3.0% over baseline
Commonly quoted: 1-1.5% risk of miscarriage |
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Term
| Complications of CVS (excluding miscarriage) |
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Definition
Bleeding and subchorionic hematoma
PROM
Rh-sensitization
Fetal abnormalities - no longer seen with skilled operators |
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Term
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Definition
16-20 weeks and after
Most important tool for detecting major anomalies
15-50% of structural anomalies can be detected
50-80% of cardiac anomalies detected after 20 weeks |
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Term
| Revised risk of major anomalies to fetus after prenatal diagnosis |
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Definition
Initial risk: 3-5%
After US: 1.5%-2.5%
After genetic testing: 1.1-2.1% |
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Term
| Fetal blood sampling (FBS) |
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Definition
More rare, not common
Used when fast results are needed, impending fetal death
2.8% risk of fetal loss |
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Term
| Preimplantation genetic diagnosis (PGD) |
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Definition
Testing on single blastomere from blastocyst (IVF)
Limitations with regard to number of probes, chance of mosaicism
No fetal risk! |
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Term
| Detection rate (sensitivity) |
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Definition
| Ratio of affected fetuses determined by screen over the total # of affected fetuses |
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Term
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Definition
| Ratio of normal fetuses thought to be affected over total # of normal fetuses |
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Term
| Time to results of prenatal lab studies |
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Definition
Karyotype: 2 weeks
FISH: 3 days
CGH: 1 week
US: Immediate |
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Term
| Cell-free fetal DNA circulating in maternal blood |
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Definition
Emerging technology
Using RT-PCR can do prenatal diagnosis
ex. Downs |
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