Prenatal Diagnostics: Ultrasound, Amniocentesis, CVS
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Questions and Answers

What is the primary purpose of ultrasonography during pregnancy?

  • To determine the mother's blood type
  • To perform genetic testing on fetal blood
  • To identify environmental teratogens
  • To assess fetal age, growth, and congenital anomalies (correct)
  • Which diagnostic method is considered to be the quickest for determining genetic abnormalities?

  • Chorionic Villus Sampling (CVS) (correct)
  • Cordocentesis
  • Maternal Serum Screening
  • Amniocentesis
  • What is a significant risk associated with Chorionic Villus Sampling (CVS)?

  • Limb reduction defects (correct)
  • High fetal stress levels
  • Infection during the procedure
  • Dehydration of the amniotic fluid
  • Which biochemical marker is commonly assessed in maternal serum screening to indicate fetal abnormalities?

    <p>AFP</p> Signup and view all the answers

    What type of sampling is performed in cordocentesis (PUBS)?

    <p>Fetal blood sampling from the umbilical cord</p> Signup and view all the answers

    How does Noninvasive Prenatal Screening (NIPS) function?

    <p>It detects fetal DNA in maternal blood</p> Signup and view all the answers

    Which statement about amniocentesis is accurate?

    <p>It can detect chromosomal abnormalities with high accuracy.</p> Signup and view all the answers

    What does maternal serum screening require after positive results?

    <p>A confirmation test such as amniocentesis</p> Signup and view all the answers

    What is the typical result of a balanced translocation between chromosome 21 and chromosome 14?

    <p>The individual appears phenotypically normal.</p> Signup and view all the answers

    Which condition is characterized by cri du chat syndrome due to a chromosomal deletion?

    <p>Partial terminal deletion on chromosome 5</p> Signup and view all the answers

    What percentage of birth defects is attributed to gene defects?

    <p>7% to 8%</p> Signup and view all the answers

    Which environmental agent is known to be a teratogen that can induce birth defects?

    <p>High doses of ionizing radiation</p> Signup and view all the answers

    What method is commonly used for diagnosing Fragile X syndrome?

    <p>Chromosome analysis or DNA testing</p> Signup and view all the answers

    Achondroplasia is a genetic disorder resulting from a mutation in which chromosome?

    <p>Chromosome 4p</p> Signup and view all the answers

    What type of chromosomal alteration results in ring chromosomes?

    <p>Loss of both ends of a chromosome</p> Signup and view all the answers

    What type of genetic disorders manifests only in homozygous individuals?

    <p>Autosomal recessive defects</p> Signup and view all the answers

    What is the term used to describe maternal factors that can cause birth defects?

    <p>Teratogens</p> Signup and view all the answers

    Which birth defect is most commonly linked to poorly controlled maternal diabetes?

    <p>Congenital heart defects</p> Signup and view all the answers

    During which weeks post-fertilization is the fetal brain considered most vulnerable?

    <p>8 to 16 weeks</p> Signup and view all the answers

    What is a common result of oligohydramnios in fetal development?

    <p>Limb deformities</p> Signup and view all the answers

    What dietary management approach can help infants at risk of defects associated with phenylketonuria?

    <p>Phenylalanine-restricted diet</p> Signup and view all the answers

    Which of the following conditions can result from multifactorial inheritance?

    <p>Cleft lip and palate</p> Signup and view all the answers

    What mechanism can lead to intrauterine amputations during fetal development?

    <p>Constriction from amniotic bands</p> Signup and view all the answers

    Which type of inheritance involves interactions between multiple genes and environmental factors?

    <p>Multifactorial inheritance</p> Signup and view all the answers

    Study Notes

    Ultrasound

    • Uses high-frequency sound waves to create images of the fetus and surrounding structures.
    • Performed transabdominally or transvaginally.
    • Can reveal fetal age, growth, congenital anomalies, amniotic fluid volume, placental position, and multiple gestations.
    • Crucial for planning pregnancy management, especially in low-birth-weight cases.
    • Measurements like crown-rump length, biparietal diameter (BPD), femur length, and abdominal circumference assess fetal development.

    Amniocentesis

    • Involves inserting a needle transabdominally into the amniotic cavity to retrieve 20–30 mL of fluid.
    • Typically performed after 14 weeks of gestation.
    • Detects chromosomal abnormalities and genetic markers with high accuracy.
    • Results take 1–2 weeks.
    • Advances in molecular biology, including PCR, have improved detection of genetic abnormalities.

    Chorionic Villus Sampling (CVS)

    • Involves collecting cells from the placental tissue.
    • Performed transabdominally or transvaginally.
    • Allows for early genetic testing (results in 2–3 days).
    • Carries a slight risk of limb reduction defects, particularly affecting the digits.

    Cordocentesis (PUBS)

    • Conducted after the 14th week.
    • Involves sampling fetal blood from the umbilical cord.
    • Diagnoses hematological diseases and chromosomal anomalies.
    • Carries a slightly higher risk of fetal loss than amniocentesis.
    • Generally reserved for high-risk cases.

    Maternal Serum Screening

    • Assesses maternal blood for biochemical markers, such as alpha-fetoprotein (AFP), which can indicate fetal abnormalities.
    • Useful in the second trimester.
    • Requires confirmatory tests, such as amniocentesis, for positive results.

    Noninvasive Prenatal Screening (NIPS)

    • Detects fetal DNA circulating in maternal blood as early as 4–6 weeks post-conception.
    • Techniques like FISH and PCR help identify genetic anomalies, including trisomies.
    • High predictive accuracy but used only for screening.
    • Invasive tests are required for confirmation.

    Deletion

    • A chromosome breaks and loses part of its structure.
    • Causes cri du chat syndrome (partial terminal deletion on the short arm of chromosome 5), characterized by a cat-like cry, microcephaly, severe mental deficiency, and congenital heart defects.

    Ring Chromosome

    • Forms when both ends of a chromosome are lost and the ends rejoin to create a ring shape.
    • Can occur with any chromosome.
    • Observed in conditions like Turner syndrome (45,X) and trisomy 18 (Edwards syndrome).

    Duplications and Inversions

    • Parts of chromosomes can be duplicated or inverted during meiosis.
    • These conditions may result in syndromes similar to those seen after the nondisjunction of entire chromosomes.

    Birth Defects Caused by Mutant Genes

    • Approximately 7% to 8% of birth defects are attributed to gene defects.
    • A mutation is a permanent, heritable change in the DNA sequence.
    • Most mutations are detrimental or lethal.
    • The rate of mutations can increase due to environmental factors, such as high doses of ionizing radiation.

    Key Genetic Disorders

    • Achondroplasia - Dominantly inherited condition resulting from a specific mutation in the fibroblast growth factor receptor 3 gene on chromosome 4p.
    • Congenital Suprarenal Hyperplasia and Microcephaly - Examples of autosomal recessive defects.

    Fragile X Syndrome

    • The second most common inherited cause of moderate intellectual disability.
    • Diagnosis involves chromosome analysis or DNA testing for CGG nucleotide expansions in the FMR1 gene.

    Birth Defects Caused By Environmental Factors

    • Human embryos are vulnerable to teratogens—agents capable of inducing birth defects or increasing their prevalence.
    • The CNS is particularly affected by teratogens.
    • Studies from Japanese atomic bomb survivors indicate that the brain is most vulnerable between 8 to 16 weeks post-fertilization.

    Maternal Factors as Teratogens

    • Maternal factors like diabetes and phenylketonuria can act as teratogens.
    • Poorly controlled maternal diabetes increases the risk of spontaneous miscarriages, brain anomalies, skeletal defects, and congenital heart issues.
    • Infants of diabetic mothers are often large and face various metabolic complications.
    • Phenylketonuria increases the risk of microcephaly, cardiac defects, and mental deficiency in offspring if not managed.
    • A phenylalanine-restricted diet can help prevent these complications.
    • Low levels of folic acid and vitamin B12 in mothers increase the risk of neural tube defects.

    Mechanical Factors as Teratogens

    • Reduced quantity of amniotic fluid (oligohydramnios) can cause deformations in the fetus.
    • These deformations include limb abnormalities like hyperextension of the knee, congenital hip dislocation, and clubfoot.
    • These issues may arise from prolonged fetal compression due to restricted mobility or a malformed uterus.
    • Intrauterine amputations or other anomalies can occur due to amniotic bands.

    Birth Defects Caused By Multifactorial Inheritance

    • Involve interactions between multiple genes and environmental factors.
    • Common defects include cleft lip, cleft palate, neural tube defects (e.g., spina bifida), pyloric stenosis, and congenital dislocation of the hip.
    • New research supports a "multiple genes of variable expression" hypothesis, indicating that a few specific genes, interacting in various ways, likely contribute to the development of these conditions.

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    Description

    This quiz covers key prenatal diagnostic techniques such as ultrasound, amniocentesis, and chorionic villus sampling (CVS). Participants will learn about the methods, purposes, and outcomes of these procedures, which are critical for monitoring fetal health and detecting potential anomalies. It's essential knowledge for anyone interested in maternal-fetal medicine.

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