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31 Cards in this Set

  • Front
  • Back
What are amniocytes?
They are the cells in amniotic fluid, which come from different sources in the pregnancy.
When is the stardard amniocentesis done?
At 16 to 20 weeks of pregnancy (in 2nd trimester).
What is the most common indication for amniocentesis?
Advanced maternal age (35 yrs or great at time of delivery).
How long does it take to receive the results of chromosomal studies?
Approx 2 weeks
How long doe sit take to receive the results of DNA & metabolic studies?
May take longer than 2 weeks epending on the number of cells needed for analysis.
What are five complications of amniocentesis?
1. Spotting after the procedure.
2. Needle stick of the fetus.
3. Infection
4. Leakage of amniotic fluid.
5. Pregnancy loss
What is the risk of pregnancy loss following amniocentesis?
0.5% (1 in 200)
How are amniocytes grown?
Directly on coverslips.
How accurate is amniocentesis for chromosomal problems?
Virtually 100% accurate.
How is chorionic villus sampling performed?
Via transcervical biopsy of chorionic villi using a flexible catheter and directed by ultrasonography.
How is amniocentesis performed?
Via transabdominal insertion of a needle under ultrasound guidance.
Can a transabdominal approach to chorionic villus sampling be performed?
Yes, using a spinal needle.
What are the two types of analyses used with chorionic villus sampling?
1. Direct analysis = analysis of chorionic ectoderm (results w/in 24 hrs).
2. Standard tissue culture = analysis of chorionic mesoderm (results in 2-4 weeks).
When is chorionic villus sampling performed?
At 10-12 weeks gestation (first trimester)
Can we evaluate for neural tube defects using chorionic villus sampling?
What are the studies performed using amniocentesis?
1. Direct analysis of amniotic fluid for alpha-fetoprotein or acetylcholinesterases (risk factors for NTDs)
2. Karyotyping & Metabolic Studies
3. Cytogenetic studies
4. Enzyme analysis
5. Molecular analysis
What studies are performed using CVS?
The same as amniocentesis except no alpha-fetoprotein or acetylcholinesterase analysis.
What are some problems/difficulties associated w/ chorionic villus sampling?
The chance for contamination by maternal cells is greatly increased over that for amniocentesis. Also, mosaicism is much more common.
What is confined placental mosaicism?
Mosaicism seen in the placenta but not in the fetus; likely seen in CVS because of the type of cells studied.
How accurate is chorionic villus sampling?
Because trophoblast analysis may not always reflect the genetic makeup of the fetus, it's not as accurate as the culturing of cells seen in amniocentesis.
How is fetal blood sampling performed?
A transabdominal needle is inserted under ultrasound guidance; it is penetrated near the insertion site into the placenta.
How can we confirm that origin of blood sample in FBS is actually from the fetus.
Measurement of MCV -- fetal RBCs are 120-160 fl, while adult RBCs are 80-95 fl.
When is FBS performed?
After 20 weeks gestation
What are the studies done in FBS?
The same except for the measurement of alpha-fetoprotein.
What is FBS generally useful for?
Detecting fetal infections and fetal anemia.
What is the risk of fetal loss after performing FBS?
Approx 1%
How accurate is FBS?
If fetal blood sample confirmed, FBS is very accurate.
What is preimplantation genetic diagnosis?
It is analysis of either the polar body or a blastomere removed from the 4-8 cell stage of blastocyst development.
Why is preimplantation genetic diagonis performed?
It was developed to be used in conjunction with IVF; it can determine whether an embryo is affected with a particular genetic disorder.
What is the main difficulty with preimplantation genetic diagnosis?
It is based on analysis of a single or very few cells.
When do fetal cells begin to cross the placenta?
In the first trimester.