Genetic counseling and prenatal diagnosis

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Genetic counseling and prenatal diagnosis

• provides parents with the knowledge to make
  intelligent, informed decisions regarding
  possible pregnancy and its outcome
• testing fetal cells, amniotic fluid, or amniotic
  membranes to detect fetal abnormalities

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Preconceptional counseling

• Many women were now postponing pregnancy and
  limiting family size, while at the same time
  striving to optimize the outcome of each
  pregnancy.
• The focus of obstetrical care has changed once
  again, from treating maternal and fetal disease
  to predicting and preventing them.

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Timing of counseling

• before conception or marriage provide
  opportunities for carrier detection, prenatal
  diagnosis or the presentation of other important
  options
• The optimal time to initiate counseling is
  therefore not during pregnancy.

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Preconceptional Counseling

• maternal disease
• diabetes mellitus
• cardiac disease, other medical diseases,
  medications
• sexually transmitted diseases
• any previous poor pregnancy outcome
• habitual abortion, ectopic pregnancy, infertility
• immunizations
• genetic risks
• nutritional counseling
• psycho-social status

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Preconceptional Counseling

• congenital anomalies
• general incidence
• major anomalies 2 - 3 live born infants at term
• leading cause of infant mortality
• minor anomalies 7 - 10
• high risk
• family history
• previous pregnancy with congenital disease
• advanced maternal age

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Purpose

• comprehend the medical facts, including the
  diagnosis, the probable course of the disorder,
  and the available management
• understand the way heredity contributes to the
  disorder and the risk recurrence for themselves
  and family members

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Purpose

• understand the options for dealing with the risk
  of recurrence
• identify those values, beliefs, goals, and
  relationships affected by the risk for or
  presence of hereditary diseasec
• choose the course of action that seems most
  appropriate to them in view of their risk, their
  family goals, and their ethical and religious
  standards

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Purpose

• make the best possible adjustment to the disorder
  or to the risk of recurrence of that disorder, or
  both, by providing supportive counseling to
  families and making referrals to appropriate
  support services or groups, or both

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Methods of prenatal diagnosis

• invasive test
• amniocentesis
• chorionic villus sampling
• cordocentesis
• preimplantation genectic diagnosis

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Methods of prenatal diagnosis

• noninvasive test
• maternal serum screening
• ultrasonography
• isolation fetal cells or DNA from maternal
  circulation

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Preimplantation genetic diagnosis

• utilizing access to gametes or embryos before 6
  days, the time at which implantation occurs
• polar body biopsy
• aspiration of one to two cells from the six to
  eight-cell embryo at 2 to 3 days
• trophectoderm biopsy of the 5- to 6-day blastocyst

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Preimplantation genetic diagnosis

• aspirating 1 - 2 of the 6 - 8 cells contained
  within the zona pellucida
• Removal of 1 or 2 cells did not affect glucose or
  pyruvate uptake or delay spontaneous hatching of
  blastocysts, the traditional indicator of normal
  embryonic development.

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Fetal cells in maternal circulation

• nested primer PCR for Y-specific DNA
• fetal trophoblasts, lymphocytes, granulocytes,
  and nucleated red blood cells (NRBCs)
• rarity of fetal cells in maternal blood (1107)
• detection rate for aneuploidy 40-59

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Fetal cells in maternal circulation
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Fetal cells in maternal circulation
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Preimplantation genetic diagnosis
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Chromosome X (green)Chromosome Y (orange)
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FISH

• hybridized to uncultured amniocyte
• three aqua signals
• 3 copies of chromosome 18

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Spectral karyotyping (SKY)
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Spectral karyotyping (SKY)