Prenatal Testing Flashcards
What does first trimester screening aka first trimester combined test?
- The blood test to measure pregnancy-associated plasma protein-A (PAPP-A) and Human chorionic gonadotropin (HCG). PAPP A and HCG. 2. Ultrasound exam to measure nuchal cord translucency
What is HCG? PAPP-A?
HCG is a glycoprotein hormone produced by the placenta during pregnancy and PAPP-A is a key regulator of insulin-like growth facroe bioavailability essential for normal fetal development
What can you visualize with ultrasound? What are the benefits? When are the routine ultrasounds?
Diagnose multiple pregnancies or major structural abnormalities. Non-invasive, no risk, highly skilled operator. Routine at 8-12 weeks and 18-20 weeks
What do you check for at 8-12 week ultrasound? 18-20
Heartbeat, gestational age, nuchal translucency, neural tube defect. At 18-20 easier visulalization of the fetus.
What could nuchal thickening be a sign of?
nuchal thickening cases present in 75% of down syndrome cases. Also present in congential heart disease, and 5% are healthy fetuses
What is alpha-fetoprotein? What could elevated levels indicate? Decreased levvels?
AFP is present in amniotic fluid, its the fetal equivalent to albumin. Leakage = elevated in 75% of neural tube defect cases or mean multiple pregnancies. Decreased in 60%-70% of Down Syndrome cases
What is the prenatal triple test for?
AFP, UG and hCG. Performed to corroborate diagnosis. When taken together, could give good indication of Down Syndrome
What is quadruple screening and when is it done?
Taken at 16 weeks of gestion. AFP, UE = unconjugated estriol, HCG, DIA - inhibin A
What does Cell-free DNA test AKA noninvasive genetic screening screen for? When? How?
Fetal aneuploidy. Week 10. Tests the number of trophpblastic DNA fragments in maternal circulation, excess means that there is a high risk of aneuploidy.
What is amniocentesis and when is it performed?
Ultrasound guided aspiration of 10-20mL of amniotic fluid. The fluid is spun down and can be used for AFP or karyotype. At 15-20 weeks of high risk of complications.
What can amniocentesis cells be used for?
Karyotype analysis, quantitative fluorescent PCS to investigate the presence and copy number of specific genes. Usually around 16 weeks because there is sufficient amniotic fluid.
What is chorionic villus sampling? What are the cells used for? How can it be done procedurally
AKA placental biopsy at later stages. Culture to expand the cells, extract DNA for biochemical tests like PCR, karyotype. Can be done trancervical or transabdominal. Can be done during the first trimester
What is fetoscopy? What are some complications?
Transabdominal endoscope, seldom performed now. 3-5% risk of miscarriage
What is twin to twin transfusion syndrome (TTTS)?
A prenatal condition in which twins share unequal amounts of the placentas blood supply resulting in the two fetuses growing at different rates
What is cordocentesis used for?
Fetoscopy used to cample blood from the fetus to diagnose blood-related disorders. From week 20
