Prenatal Diagnosis Flashcards
What are differences between a prenatal diagnostic test & prenatal screening
Screening: determines chance of genetic condition, negative = low chance not zero, positive = increased chance, no associated risk, identifies patients to offer additional testing to, widely available & affordable
Dx testing: provides/ rules out diagnosis, negative = usually rules out, positive= provides diagnosis, risk associated with procedure, usually more costly
What are invasive/diagnostic testing options
Chorionic villi sampling, amniocentesis, percutaneous umbilical blood sampling
During what gestational weeks can a CVS be performed
10w3d-13w6d
What are pros & cons of a CVS
Pros: first trimester & earliest diagnostic results
Cons: higher miscarriage risk (1 in 200), limb reductions in early <10 weeks, possibility for mosaicism (1-2%), maternal cell contamination possible, can’t perform all same tests as ammio
During what gestational weeks can an amniocentesis be performed
15w0d-20w6d
What are pros & cons of an amniocentesis
Pros: lower miscarriage risk (1/300), can test for neural tube defects, looks at actual fetal cells, lower risk of mosaicism than CVS
Cons: chorion & amnion can be fused, increased clubfoot risk in early, risk for needle puncture, possible maternal cell contamination
What is PUBS & what does it tell us
needle guided via ultrasound to fetal umbilical cord for fetal blood sample. Can test for fetal anemia & provide blood transfusions in cases of maternal alloimmunization or infection, can also help evaluate mosaicism found on amnio
Which diagnostic testing results come back first
FISH, 36-48 hours
How long do microarray & karyotype results take
Microarray 7-10 days, karyotype 1-3 weeks
What are some important things to discuss with consenting for prenatal microarray
Will identify almost all abnormalities detected on karyotype
Some conditions have varying severity which can not be predicted
Consanguinity can be found
Possibility for uncertain variants
In what diagnostic procedure can AFP be measured & what is the follow up testing
Amniocentesis
Elevated - reflux to AChE, if also present this is diagnostic for neural tube defect
What are indications for prenatal diagnostic testing
Advanced age, abnormal screening, previous pregnancy or child with condition, ultrasound findings, patient with known chromosome rearrangement, increased risk for single gene condition, wanting one
What event must have occurred for amniocentesis to be possible
Fusion of the amnion & chorion
