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Genetics > Prenatal > Flashcards

Prenatal Flashcards

1
Q

Name 9 conditions that ACMG recommends carrier screening for in individuals of Ashkenazi Jewish descent

A
  1. Tay Sachs
  2. Canavan disease
  3. Gaucher disease
  4. Cystic fibrosis (founder mutations)
  5. Familial dysautonomia
  6. Niemann Pick Type A
  7. Fanconi anemia Group C
  8. Bloom syndrome
  9. Mucolipidosis Type IV
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2
Q

What is the risk of miscarriage associated with CVS or amniocentesis?

A

Amniocentesis: 1/400 or 0.25%
CVS: about 1%

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3
Q

What are the 3 chromosomal mechanisms for Down syndrome?

A

Trisomy 21-~95%
Robertsonian translocation 5%
Isochromosome 21 ~1%

Important to get the karyotype to know the mechanism and recurrence risk

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4
Q

How many fetuses with Down syndrome will result in a live birth?

A

20-25%

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5
Q

How many fetuses with Trisomy 18 will result in a live birth?

A

5%

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6
Q

True or false: Turner syndrome is associated with advanced maternal age.

A

False

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7
Q

Name 5 conditions tested for by California State serum screening

A
  1. Down syndrome
  2. Trisomy 18
  3. Neural tube defects
  4. Anterior abdominal wall defects
  5. Smith Lemli Opitz syndrome
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8
Q

Name 4 risk factors identified in neural tube defects.

A
  1. Poorly controlled maternal diabetes
  2. Certain anti-seizure medications
  3. Low serum folic acid levels
  4. Elevated maternal temps around 4-6 weeks (fever/infection or hot tub, sauna)
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9
Q

When you see a California State prenatal screen positive for SLO, what else should you consider?

A
  1. Other congenital anomalies
  2. Fetal demise
  3. Steroid sulfatase deficiency (if low unconjugated estriol)
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10
Q

Name the 5 hormones evaluated in California State Maternal Serum Screening program.

A
  1. PAPP-A
  2. Inhibin
  3. HCG
  4. AFP
  5. Unconjugated estriol
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11
Q

What is PAPP-A? What is it produced by?

A

PAPP-A= pregnancy associated plasma protein
Made by fetus and placenta
Increases with gestation

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12
Q

What produces HCG? What is the typical pattern?

A

HCG is produced by placenta
Usually rapid rise in early pregnancy, then decline later in pregnancy
Used in both the first and second trimester screening

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13
Q

What is AFP produced by? What is the typical pattern?

A

AFP produced by fetal liver
Released into fetal circulation and amniotic fluid
Small amount detectable in mom’s bloodstream late in first trimester and increases in second trimester

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14
Q

What produces inhibin? What is the typical pattern?

A

Inhibin is produced by the ovaries and placenta

Usually rises early in pregnancy, declines after 10 weeks, stable between 15-20 weeks

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15
Q

What produces unconjugated estriol? What is the typical pattern?

A

Unconjugated estriol is produced by the fetal adrenal glands, fetal liver, placenta
Levels rise throughout the pregnancy
Used as analyte for second trimester screening

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16
Q

Which analytes are used for first trimester maternal serum screen?

A
  1. PAPP-A

2. HCG

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17
Q

Which analytes are used for second trimester maternal serum screen?

A
  1. HCG
  2. AFP
  3. inhibin
  4. UE3 (unconjugated estriol)
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18
Q

When can a nuchal translucency be obtained?

A

between 11 weeks and 2 days and 14 weeks and 2 days

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19
Q

What is the purpose of performing an NT?

A

Increase detection rates of T18 and T21

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20
Q

What is included in first trimester combined screening?

A

1st trimester analytes (PAPP-A, HCG) and NT ultrasound

21
Q

What is included in serum integrated screening?

A

1st and 2nd trimester analytes, no NT ultrasound

22
Q

What is included in sequential integrated screening?

A

1st and 2nd trimester analytes + NT ultrasound

23
Q

What is included in the quad screen?

A

2nd trimester analytes only

24
Q

What condition follows this analyte pattern on maternal serum screening?

Decreased: PAPP-A, AFP, unconjugated estriol,
Increased: HCG, inhibin

A

Trisomy 21

25
Q

What condition follows this analyte pattern on maternal serum screening?

Decreased: PAPP-A, HCG, AFP, uE3, HCG, inhibin

A

Trisomy 18

26
Q

What conditions should you consider with an elevated AFP?

A
  1. Open neural tube defect
  2. anterior abdominal wall defect
  3. false positive
27
Q

Name 5 reasons for a false positive NIPT

A 
1. Confined placental mosaicism
estimated in ~5% of pregnancies
2. Abnormal maternal chromosomes
-maternal mosaic Turner syndrome
3. Vanishing twin/twin demise
4. lab error
5. maternal metastatic disease
28
Q

Name 1 reason for a false negative NIPT

A
  1. Low fetal fraction
    - GA less than 10 weeks
    - Fetal fraction decreases with increased maternal weight/obesity
29
Q

What is the carrier rate for CF in the Caucasian population?

30
Q

Does ACOG recommend CF carrier screening for all women?

A

Yes–one pregnancy, does not need to be repeated

Regardless of ethnicity although detection rates on common mutation panel vary by ethnicity

31
Q

When should Ashkenazi Jewish carrier screening be offered?

A

Offer if at least one grandparent is of Ashkenazi Jewish ancestry (25%)

32
Q

Who should be offered Tay Sachs screening?

A
  1. French Canadians
  2. Cajuns
  3. Ashkenazi Jewish
  4. Family hx of Tay Sachs

DNA testing is not appropriate for non-Jewish populations
Best testing for all ethnicities is Hexosaminidase A enzyme analysis

33
Q

Who should be offered hemoglobinopathy screening? What tests?

A

ACOG recommends screening for individuals of African, Mediterranean, Southeast Asian descent (Japan & Korea are low-risk)

MCV and hemoglobinelectrophoresis

34
Q

Which neural tube defect has the highest recurrence risk?

A

myelomeningocele (2-5%)

Genetics in Medicine (2005) 7, 64–67

35
Q

What are the cytogenetic mechanisms that cause Down syndrome and their recurrence risks?

A
  1. Trisomy 21 (95%)
    (due to maternal non-disjunction event, mostly in meiosis I)
    -recurrence risk 1% unless mother’s age gives higher risk for aneuploidies
  2. Unbalanced translocation (3-4%)
    -50% parent carries a balanced translocation
    -50% are de novo events
    -if parent carries a balanced 21:21 translocation there is 100% risk of recurrence
  3. Mosaicism (1%)
    -post-zygotic mitotic error
    -low recurrence risk (usu < 1%)
36
Q

What anomalies are most frequently associated with a single umbilical artery?

A

Single umbilical artery occurs I 1/100 -1/400 pregnancies

  • genitourinary, cardiac, and CNS can be seen
  • SUA associated with higher rates of malformation, aneuploidy, and poor growth/IUGR
37
Q

Name some ultrasound markers for Trisomy 21.

A
  1. Absent nasal bone
  2. Intracardiac Echogenic focus
  3. Echogenic bowel
  4. Shortened proximal long bones (femurs, humerus)
  5. increased nuchal translucency
  6. pyelectasis
    8, Structural anomalies -cardiac, intestinal atresia, ventriculomegaly
38
Q

A fetal karyotype from amniocentesis shows a balanced translocation. Parental karyotypes were normal (ie therefore de novo). Is there any risk of abnormalities?

A

=Yes, 5% of some developmental delay or other abnormality

  • most balanced rearrangements have no phenotype
  • but if breakpoint of the translocation disrupts a gene or the deletion occurs at a breakpoint, there is potential for an abnormal phenotype
39
Q

What findings are suggestive of a lethal skeletal dysplasia?

A

Skeletal dysplasia should be considered in a fetus with long bone measurements <5th percentiles or >3 SD below the mean (especially in setting of normal OFC)

Lethality suggested by:
1. A chest to-
abdominal circumference ratio of < 0.6
2. femur length
to abdominal circumference ratio of < 0.16

There are exceptions to this, but generally findings strongly suggestive of lethality

40
Q

true or false: there may be an increased rate of hemangiomas after CVS.

41
Q

Which has a higher miscarriage rate: CVS or early 2nd trimester amniocentesis?

A

=early amniocentesis (2%) vs CVS (1%)

42
Q

True or false: in most cases of premature ROM after amniocentesis, amniotic fluid will reaccumulate within 3 weeks and 90% fetal survival.

43
Q

True or false: risk for neural tube defects, cardiac defects, and orofacial clefts increase with increasing maternal BMI.

44
Q

Among male causes of infertility, which of the following would be most likely to be encountered in a man with OLIGOSPERMIA?

a. balanced translocation
b. fragile X mutation
c. Delta F508 mutation
d. sex chromosome aneuploidy
e. sertoli cell only syndrome

A

=balanced translocation

-3-5% of men with oligospermia carry a balanced translocation

45
Q

Among males causes of infertility, which of the following would be most likely to be encountered in the man with non-obstructive azoospermia?

a. balanced translocation
b. fragile X mutation
c. Delta F508 mutation
d. sertoli cell only syndrome
e. sex chromosome aneuploidy

A

=sex chromosome aneuploidy

46
Q

Among male causes of infertility, which of the following would be most likely to be encountered in the man with obstructive azoospermia?

a. balanced translocation
b. DAZ deletion
c. Delta F508 mutation
d. Fragile X premutation
e. sex chromosome aneuploidy

A

=delta F508 mutation

CF mutation associated with obstructive azoospermia due to congenital bilateral absence of the vas deferens

47
Q

All of the following are soft markers associated with Down syndrome EXCEPT:

a. choroid plexus cyst
b. echogenic bowel
c. echogenic cardiac focus
d. renal pyelectasis
e. shortened femur

A

=choroid plexus cyst (associated with T18 but not T21).

48
Q

Which of the following soft markers has the highest relative risk for Down syndrome?

a. absent nasal bone
b. echogenic bowel
c. echogenic cardiac focus
d. renal pyelectasis
e. shortened femur

A

echogenic bowel

Increases likelihood of T21 5-7 fold

49
Q

Which of the following birth defects has the highest risk in significantly obese (BMI 40 or greater) women?

a. neural tube defects
b. cardiac defects
c. orofacial clefting

A

=neural tube defects

Genetics (16 decks)

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