Prenatal diagnosis of genetic disorders and congenital defects Flashcards
(25 cards)
What is the principal aim of prenatal diagnosis?
To supply at-risk families with information for informed choices during pregnancy.
What are some potential benefits of prenatal testing?
- Providing reassurance to at-risk families when the result is normal
- Providing risk information to couples hesitant to begin a pregnancy
- Allowing psychological preparation for the birth of an affected baby
- Helping healthcare professionals plan delivery and care for diagnosed infants
- Providing risk information for couples considering pregnancy termination.
What is an example of a population screening test in prenatal diagnosis?
Analysis of maternal serum at 15 weeks’ gestation for α-fetoprotein (AFP) levels.
What is amniocentesis?
The withdrawal of amniotic fluid during pregnancy for diagnostic testing.
What does amniocentesis analyze?
- Amniocytes for cytogenetic studies
- Biochemical assays
- DNA-based diagnosis.
What is the risk of fetal loss associated with amniocentesis?
No more than 0.2% to 0.3% above the background risk.
What is the purpose of fluorescence in situ hybridization (FISH) in amniocentesis?
To provide an indication of fetal aneuploidy in 1 to 2 days.
What are the indications for prenatal diagnosis by amniocentesis?
- Maternal age >35 years
- Previous child with chromosome abnormality
- History of structural chromosome abnormality in one parent
- Family history of genetic defect
- Increased risk of neural tube defect due to family history
- Abnormal screening results.
What is pseudomosaicism in the context of amniocentesis?
Apparent mosaicism caused by the generation of an extra chromosome during in vitro cell culture.
What is confined placental mosaicism?
Mosaicism observed in placental material that is not present in the fetus.
What is percutaneous umbilical blood sampling (PUBS)?
A method to access fetal blood through ultrasound-guided puncture of the umbilical cord.
What are the primary applications of PUBS?
- Cytogenetic analysis of fetuses with structural anomalies
- Diagnosis of hematological diseases
- Confirmation of mosaicism.
What are the measurable enzymes for Maple syrup urine disease?
Branched-chain ketoacid decarboxylase
What is the significant advantage of using Magnetic Resonance Imaging (MRI) over ultrasound?
Greater resolution
What is the primary purpose of noninvasive prenatal screening (NIPS)?
To isolate fetal cells and cell-free fetal DNA from maternal blood
What technique is often used to analyze cell-free DNA (cfDNA) for aneuploidy detection?
High-throughput sequencing
What is the purpose of performing preimplantation genetic diagnosis (PGD)?
To diagnose genetic diseases before embryo implantation
What is tested to determine if an egg contains a disease-causing mutation?
The polar body’s DNA is tested
This method assumes that if the polar body contains a mutation, the egg does not.
What is the assumption made when the polar body contains a mutation?
The egg does not contain the mutation
This is based on the genetic contribution of the ovum.
In what cases is polar body diagnosis most useful?
- When only the mother is at risk for transmitting a mutation
- When testing for aneuploidy
Most aneuploidies are contributed by the mother.
What does PGD stand for?
Preimplantation Genetic Diagnosis
PGD is commonly used in conjunction with in vitro fertilization.
Who commonly uses PGD?
Couples who have resorted to in vitro fertilization
They wish to test for diagnosable genetic conditions.
What is a limitation of PGD?
It is costly and technically challenging
Its availability is still somewhat limited.
What types of cells can preimplantation genetic diagnosis be carried out on?
- Polar bodies
- Blastomeres
- Blastocyst cells
Various techniques like PCR analysis, FISH, aCGH, or sequencing can be performed.
