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Lifecycle Unit 2 Test > Prenatal Diagnosis > Flashcards

Prenatal Diagnosis Flashcards

1
Q

Basic Principles

A

a. Screening the General Population for Common Disorders i. Down Syndrome ii. Congenital Birth Defectsb. Offer Screening to Risk Groups for Clustered Disorders i. Cystic Fibrosis ii. Tay Sachsc. Offer Screening to Families with Known Disorders

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2
Q

Components of Screening

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  1. Clinical history (maternal age)2. Family History: pedigree analysis3. Diagnostic tests in parents i. Hgb electrophoresis ( Sickle cell disease ) ii. DNA analysis for single gene disorders ( CF ) iii. Karyotypes ( Prior infant with aneuploidy )4. Screening tests for the fetus i. Maternal serum biochemical screening ii. Ultrasound ( first trimester with nuchal translucency ) iii. Ultrasound ( fetal anatomy survey) iv. Maternal serum cell free fetal DNA + microarray5. Options counseling
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3
Q

Targeted or Population Screening

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a. Targeted–> specific individuals due to history or exam1. Screen with history, exam, routine labs, or other data2. Examine highest risk subgroups, especially for rare diseases3. Could be screen-in or screen-out (example, GDM testing) -may need to be required4. Counseling issues are the same b. Population1. Everyone screened to identify disease or disease risk2. Can be opt-out 3. Example: neonatal metabolic screening 4. We offer screening or diagnosis to all for fetal evaluation

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4
Q

Shared Decision MakingMake sure to discuss the Screening and Diagnostic

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a. Screening tests for the fetus 1. Maternal serum biochemical screening 2. Ultrasound ( first trimester with nuchal translucency) 3. Ultrasound ( fetal anatomy survey) 4. Maternal serum cell free fetal DNA + microarrayb. Diagnostic tests for the fetus 1. Chorionic villus sampling 2. Amniocentesisc. Options counseling

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5
Q

Screening and Diagnostic Tests

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a. Screening: may not diagnos, but figure out risk -Assess risk -Quick -Noninvasive -?Less expensive -Widely accessible -High NPV -Low false positives -First step only -Pre and post test counselingb. Diagnostic–> gold standardtestAs close to truth as possibleMaybe longerMaybe invasiveMaybe special trainingGives a diagnosis if completedLast or first stepRisk and pre/post test counseling

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6
Q

Prenatal Screening

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a. Reassurance for at-risk familiesb. Prepare for the birth of a baby with anomaliesc. Develop plans for monitoring and for neonatal cared. Provide data to allow continuation decision makinge. MOST SCREENING (~98%) is normalf. MOST anomalies are in normal, low risk patients

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7
Q

Ultrasound

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a. NIH and ACOG indications for US: - Fetal presentation - Suspected multiple gestation - Establish due date - Suspected fetal death - Suspected oligohydraminos - Abnormal AFP b. Other Indications -Fetal Anatomy Survey -Placenta Location -Maternal Uterine/Pelvic Anatomy -Cervical Length Assessmentc. Technique is trans-abdominal or trans-vaginal approach

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8
Q

Estimating Gestational Age

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a. First Trimester i. Crown-rump lengthb. Second and third trimester i. Biparietal Diameter (BPD) ii. Abdominal Circumference (AC) iii. Femur Length (FL) iv. Earlier the US, the more accurate the datingc. Up to 9 weeks: +/- 5 days i. 9 weeks to 16 weeks: 7 days ii. 16 to 22 weeks: 10 days iii. 22 to 28 weeks: 14 days iv. 28 weeks on: 21 days

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9
Q

Transvaginal Ultrasound

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a. Long probe that goes in the vaginab. Will use to estimate shit

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10
Q

Estimating Age: Crown-Rump Length

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a. Used for the 1st trimester for gestational ageb. Very accurate predictor

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11
Q

First Trimester Analytes

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a. Look at Nuchal Bone and Nuchal Translucencyb. Can use this to predict 21 trisomy (down syndrome)

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12
Q

First Tri Screening (11-14w)

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a. Ultrasound i. 82-87 % detection of Down Syndrome ii. 5% screen positive iii. Larger NT is higher risk and higher risk of other anomalies iv. Nasal bone adds additional sensitivityb. Serum Biochemistry i. hCG ii. PAPP-Ac. Maternal factors i. Age ii. Prior h/o aneuploidy iii. Weight iv. Race v. Number of fetuses

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13
Q

Cervix on Transvaginal Ultrasound(after ~16w)

A

a. Cervic can be screened early in pregnancyb. See if there are any Preterm birth risksc. Measure cervix–> length correlates with risk for early birth

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14
Q

Transvaginal cervical length

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a. Can use cervical length as assessment for preterm birth

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15
Q

Trans-abdominal Ultrasound

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Estimating Age: Biparietal DiameterCan use this for screening as well–> age and date fetus

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16
Q

Estimating Age: Abdominal Circumference

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a. Can use this for screening as wellb. Age and date the fetus, measuring its growth

17
Q

Estimating Age: Femur Length

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a. Can use this for screening as wellb. Age and date the fetus, measuring its growth

18
Q

Hadlock Formula for Fetal WeightLog 10 birth weight =

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1.4787 + 0.001837 (BPD) 2 +0.0458 (AC) + 0.158 (FL) – 0.003343 (AC × FL)Algorithim with these different measurements

19
Q

Second Trimester Aneuploidy and ONTD Screening

A

a. Trisomy 13, 18 and 21b. Open Neural Tube Defectsc. Maternal Serum Analytes i. Alpha-feto protein (ONTD) ii. Unconjugated estriol iii. Human chorionic gonadotropin iv. Dimeric Inhibin-Ad, Ultrasound i. Nuchal translucency, anatomy

20
Q

Complications of Down Syndrome

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NeurologicalMost individuals with Down syndrome have mild (IQ: 50–69) or moderate (IQ: 35–50) intellectual disability with some cases having severe (IQ: 20–35) difficulties.Many developmental milestones are delayed with the ability to crawl typically occurring around 8 months rather than 5 months and the ability to walk independently typically occurring around 21 months rather than 14 months.[32]Children and adults with Down syndrome are at increased risk of epileptic seizures, which occur in 5–10% of children and up to 50% of adults.SensesBrushfield spots, visible in the irises of a baby with Down syndromeHearing and vision disorders occur in more than half of people with Down syndromeHeartThe rate of congenital heart disease in newborns with Down syndrome is around 40%, Of those with heart disease, about 80% have an atrioventricular septal defect or ventricular septal defect with the former being more common. Mitral valve problems become common as people age, even in those without heart problems at birth. Other problems that may occur include tetralogy of Fallot and patent ductus arteriosus.[39] People with Down syndrome have a lower risk of hardening of the arteries.[3]*CancerCancers of the blood are 10 to 15 times more common in children with Down syndrome.[18] In particular, acute lymphoblastic leukemia is 20 times more common and the megakaryoblastic form of acute myeloid leukemia is 500 times more commonEndocrineProblems of the thyroid gland occur in 20–50% of individuals with Down syndrome.[3][18] Low thyroid is the most common form, occurring in almost half of all individuals.GastrointestinalConstipation occurs in nearly half of people with Down syndrome and may result in changes in behavior.[18] One potential cause is Hirschsprung’s disease, occurring in 2–15%, which is due to a lack of nerve cells controlling the colon.Other frequent congenital problems include duodenal atresia, pyloric stenosis, Meckel diverticulum, and imperforate anus.[39] Celiac disease affects about 7–20% and gastroesophageal reflux disease is also more common

21
Q

Increased Risk for Aneuploidy

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a. Maternal age >35 at deliveryb. Dizygotic twins and maternal age >31c. Previous aneuploidyd. Parent with chromosomal translocation or inversione. History of triploidyf. Recurrent early pregnancy lossg. Patient or partner has aneuploidyh. Major structural defect on ultrasound

22
Q

Patterns of Analytes*Know this

A

a. Trisomy 21 *1. MS-AFP - Low 2. uE3 - Low *3. HCG -Increased 4. Inhibin A - Increased 5. PAPP-A - Decreasedb. Trisomy 18 *1. MS-AFP - Low 2. uE3 - Low *3. HCG -Increased 4. Inhibin A - Not used 5. PAPP-A - Decreasedc. Trisomy 13 1. PAPP-A- Decreasedd. Neural Tube Defect 1. MS-AFP- Increased 2. uE3 - Normal 3. HCG -Normal

23
Q

Cell Free Fetal DNA Testing

A

a. Non-invasive test with no miscarriage risk b. High sensitivity & specificity c. Available early in gestation d. Patients at increased risk for aneuploidy -AMA -Family history -Abnormal serum testing -Abnormal ultrasound

24
Q

Principles of Fetal Trisomy 21Maternal Blood Sample Using DNA Sequencing

A

Several blood markers can be measured to predict the risk of Down syndrome during the first or second trimester. Testing in both trimesters is sometimes recommended and test results are often combined with ultrasound resultsIn the second trimester, often two or three tests are used in combination with two or three of: α-fetoprotein, unconjugated estriol, total hCG, and free βhCG detecting about 60–70% of cases.Serum tests *1. MS-AFP - Low *2. uE3 - Low *3. HCG -Increased 4. Inhibin A - Increased 5. PAPP-A - Decreased

25
Q

Massively Parallel Sequencing

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Does not differentiate fetal vs. maternal DNA.Over-representation of Chromosome 21 fragments in an affected pregnancy is significant and can be measured with high precision

26
Q

Consider this analyte: AFP

A

Where is alpha feto protein made?What is alpha feto protein?AFP is a major plasma protein produced by the yolk sac and the liver during fetal development. It is thought to be the fetal form of serum albumin. AFP binds to copper, nickel, fatty acids and bilirubin and is found in monomeric, dimeric and trimeric forms.How is AFP cleared?What is it a marker for?AFP is measured in pregnant women through the analysis of maternal blood or amniotic fluid, as a screening test for a subset of developmental abnormalities. Some of the diseases in which AFP will be elevated in a person are listed below:-Omphalocele -Hepatocellular carcinoma/hepatoma: ↑ α-fetoproteinNeural tube defects: ↑ α-fetoprotein in amniotic fluid and maternal serum-Nonseminomatous germ cell tumors-Yolk sac tumorAtaxia telangiectasia: Elevation of AFP is used as one factor in the diagnosis of ataxia telangiectasia.Tumors: AFP can also be used as a biomarker to detect a subset of tumors in non-pregnant women, men, and children. A level above 500 nanograms/milliliter of AFP in adults can be indicative of hepatocellular carcinoma, germ cell tumors, and metastatic cancers of the liver.

27
Q

Elevated AFP is NOT only ONTD

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a. Incorrect datingb. Maternal – fetal hemorrhagec. Multiple gestationsd. Other anomaliese. Placentation abnormalitiesf. Unexplained

28
Q

Rates of DS Detection at Various False Pos Rates False Pos Rates at Various DS Detection Rates

A

All tests include maternal age and gestational ageDouble test-AFP and hCG, triple test-; quad-, combined test-PAPP-A, free beta hCG, and NT, IS-PAPP-A, NT, quad screenWhen evaluating the effectiveness of screening tests you need to consider the sensitivity (detection rate) as well as the FP rate which influences how many women will have an invasive procedure based on the result of the screening test (assuming that all women who test positive elect to have the invasive test)This also has an effect on the number of unaffected fetuses lost.

29
Q

Second Trimester Markers of Down Syndrome

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Nuchal thickeningNasal bone hypoplasia/absenceBrachycephalyShort ear lengthEchogenic intracardiac focusEchogenic bowelRenal pelvis dilationWidened iliac angleClinodactylyShort femur or short humerus

30
Q

Diagnostic Tests (Gold Standard)

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a. Amniocentesisb. Chorionic Villus Samplingc. Percutaneous Blood Sampling

31
Q

Amniocentesis

A

Performed after 15 weeks

32
Q

Chorionic Villus Sampling

A

a. Detects genetic, metabolic & DNA abnormalitiesb. Sample from developing placentac. Performed at 10-13 weeksd. Does not detect neural tube defectse. Earlier than amniocentesisf. Abdominal or transvaginal route

33
Q

Know the Trisomy and Neural Tube patterns

A

a. Trisomy 21 *1. MS-AFP - Low 2. uE3 - Low *3. HCG -Increased 4. Inhibin A - Increased 5. PAPP-A - Decreasedb. Trisomy 18 *1. MS-AFP - Low 2. uE3 - Low *3. HCG -Increased 4. Inhibin A - Not used 5. PAPP-A - Decreasedc. Trisomy 13 1. PAPP-A- Decreasedd. Neural Tube Defect 1. MS-AFP- Increased 2. uE3 - Normal 3. HCG -Normal

34
Q

Trisomy 21 vs Neural Tube

A

Trisomy 21 *1. MS-AFP - Low 2. uE3 - Low *3. HCG -Increased 4. Inhibin A - Increased 5. PAPP-A - Decreased Neural Tube Defect 1. MS-AFP- Increased 2. uE3 - Normal 3. HCG -Normal

35
Q

Trisomy 18 and 13 compared

A

Trisomy 18 *1. MS-AFP - Low 2. uE3 - Low *3. HCG -Increased 4. Inhibin A - Not used 5. PAPP-A - DecreasedTrisomy 13 1. PAPP-A- Decreased

Lifecycle Unit 2 Test (19 decks)

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