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Genetics MBS > Prenatal Diagnosis > Flashcards

Prenatal Diagnosis Flashcards

1
Q

goals of prenatal diagnosis

A
  • provide info to parents about testing options
  • detect anaomalies/disorders
  • counsel/support
  • fetal therapy if available
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2
Q

noninvasive screens

A
  • maternal serum
  • sequencing of cell-free DNA in maternal plasma
  • prenatal ultrasound
  • fetal MRI
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3
Q

Invasive Diagnostics

A
  • chorionic villus smapling CVS
  • amniocentesis
  • cordocentesis
  • fetal biopsy
  • pre-implantation genetic diagnosis PGD
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4
Q

first trimester tests/screens

A
  • ultrasound
  • NIPT
  • NT, serum screen
  • CVS
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5
Q

second trimester test

A
  • 2nd serum
  • amniocentesis
  • fetal anomaly scan
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6
Q

tests arent done after second trimester…

A

because a decision of whether the baby is to be kept or not needs to happen within a certain time frame (legally)

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7
Q

first screening question

A

how old are you?

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8
Q

indications for invasive prenatal diagnosis

A
  • maternal age 35 or older at time of delivery
  • major anomoly on ultrasound
  • abnormal maternal serum
  • positive cell free DNA
  • fmaily history of single gene disorder/chromosomal
  • maternal anxiety
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9
Q

screening for fetal down syndrome

A
  • measure placental proteins
  • nunchal translucency screening
  • offer invasive test
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10
Q

nuchal translucency

A
  • normal fluid filled space between back of fetal neck and overlying skin
  • increased in fetuses with: down syndrome, turner syndrome, trisomy 18, trisomy 13, triploidy
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11
Q

maternal serum screening

-what must be known

A
  • measurement of proteins produced by the fetus or placenta
  • calculated relative to population standards
  • mom and gest age must be known as well as race, diabetes, and smoking
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12
Q

benefits of CVS

  • cells are what so you can do what
  • preferable to…
  • does not detect…
A
  • done at 11 weeks, restoring privacy to reproductive decision
  • mitotically active cells = rapid karyotype
  • tissue obtained is preferable for DNA analysis
  • mosaic trisomy detected identifying fetuses risk for uniparental disomy
  • does not detect mosaicism in the fetus itself
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13
Q

risk of cVS

A
  • elevated risk of fetal loss
  • slightly elevated risk of maternal infection
  • limb malformation syndrome
  • confined placental mosaicism in 1% of cases
  • amniotic fluid alpha fetoprotein not assayed (not info on neural tube defects
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14
Q

amniocentesis

  • cell arise from
  • timeline
  • associated birth defects
  • type of analysis used
  • risk
  • mosaicism
A
  • cells from amniotic fluid arise from fetal mouth and urniary bladder and amnios
  • prefered at 15-17 weeks
  • early amniocentesis associated with fetal club foot
  • FISH analysis of non-dividing cells permits rapid diagnosis of aneuploidy
  • risk of miscarriage 1/200 to1/600
  • mosaicism in placenta not detected
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15
Q

fetal cell-free DNA

  • found where
  • origin
  • used for
A
  • surprisingly high amounts of fetal DNA circulate in the blood of pregnant women
  • origin of fetal DNA is in the placenta
  • in 2011 started to be used as an advanced screen for fetal aneuploidy: trisomy 13, 18, 21; screening for sex chromosome anomalies, providing info on fetal sex
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16
Q

NIPT is safer for…

A
  • high risk women
  • less than 0.1% of trisomy 21 are missed (false neg)
  • 95% of women do not have aneuploidy detected
17
Q

Limitations of NIPT

A
  • finite amount of fetal DNA
  • may not be detectable in overweight women as the concentration will be lower
  • less reliable in twin pregnancies
  • will not detect open neural tube defects such as spina bifida
18
Q

ultrasound findings in down syndrome

A

-increased sandal gap

19
Q

benefit of 2D ultrasound to 3D 4D and HD

A
  • can see internal anomalies using 2D ultrasound

- higher can can see exterior changes easily

20
Q

preimplantation genetic diagnosis

A
  • the process of screening the embryos for genetic abnormalities prior to transferring to the uterus
  • requires the use of IVF
  • may also require intrcytoplasmic sperm injections
  • embryo biopsy on 3rd day
  • FISH or PCR analysis of single blastomere
  • comparable to success rate of natural pregnancy
  • expensive 12k-18k per cycle
21
Q

clinical apps for PGD

A
  • single gene diagnosis by PCR
  • familial chromosome rearrangement by FISH
  • fetal sex selection, only if it is at a high risk for certain genetic conditions (x-linked)
22
Q

controversial issues with PGD

A
  • pre disposition for adult onset disorders
  • aneuploidy screening by FISH
  • sex selection
  • creation of HLS matched stem cell donors

Genetics MBS (12 decks)

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