Prenatal Diagnosis Flashcards
What is prenatal testing?
It is used to detect abnormalities in a fetus’ genes or chromosomes before birth-offered when there is an increased risk of having a child with a genetic condition due to mother’s age, family history, ethnicity, or US exam.
a needle is inserted transabdominally into the amniotic cavity, and a sample of aniotic fluid is withdrawn
amniocentesis
What is amniocentesis used to look at?
chromosome studies, enzyme measurements, and or DNA analysis
What is an AFP elevation associated with?
an open NTD
Where is AFP produced?
mainly in the liver, secreted into the fetal circulation, and excreted through the kidneys into the amniotic fluid by fetal urine
What are the two approaches for Chorionic Villus sampling?
transcervical and transabdominal
What does a sample from CVS obtain? What is it used for?
fetal trophoblastic cells used for DNA and chromosome analysis
When is CVS performed?
During 10-12 week of pregnancy
When is amniocentesis preformed?
during 15-16 week of pregnancy
the highly vascular outer embryonic membrane that is associated with the allantois in the formation of the placenta
chorion
When is maternal serum screening performed?
during the 1st and 2nd trimesters
When is the maternal serum screen for alpha-fetoprotein for alpha-fetoprotein?
16 weeks
What decreases the incidence of NTDs?
folic acid supplementation starting at least 1 month before conception and continuing through the first trimester reduces by nearly 75%
when does first trimester screening take place?
weeks 11 and 13
When does second trimester screening take place?
weeks 15 and 20
what is abnormally observed in the PAPP-A and free B-hCG levels in the first trimester?
PAPP-A and free B-hCG levels depressed below normal in all trisomies except B-hCG is elevated in Down’s syndrome
What is abnormally observed in uE3, AFP, Free B-hCG and inhibin 3 in the second trimester?
Maternal serum AFP, free B-hCG, uE3 and inhibin A are all depressed below normal in all trisomies, except B-hCG and inhibin A are elevated in Down’s Syndrome
What is ultrasound used for?
to identify multiple pregnancies, detect fatal malformations such as congenital heart defects, neural tube defects, cleft lip and palate
Ultrasound for chromosomal aneuploidy uses what?
fetal aneuploidy marker of nuchal translucency (NT)
What does the fetal aneuploidy marker of nuchal translucency (NT) do?
quantifies the subcutaneous translucency between the skin and soft tissue overlying the cervical spine
What are fetal echocardiograms used for?
analysis of congenital heart defects
When is the earliest that an echocardiogram can be conducted?
16-18 weeks gestation
When can fetal sex be determined?
After the 15th week
How is preimplantation genetic diagnosis done?
remove a polar body or biopsy a single cell of analysis prior to in vitro fertilization
