Lecture 18
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Questions and Answers

What is the definition of twinning?

  • The birth of quadruplets
  • The birth of conjoined twins
  • The bearing of two children at one birth (correct)
  • The birth of triplets

    • What percentage of twins are dizygotic (fraternal) twins?

  • 70%
  • 60%
  • 80%
  • 90% (correct)

    • What is the incidence of monozygotic (identical) twins per 1000 births?

  • 5-6 per 1000 births
  • 3-4 per 1000 births (correct)
  • 7-8 per 1000 births
  • 1-2 per 1000 births

    • What is a factor that increases the chances of twinning?

    <p>Advancing age of the mother</p> Signup and view all the answers

    What is the racial group with the highest incidence of twinning?

    <p>Black African women</p> Signup and view all the answers

    What is a method that increases the chances of twinning?

    <p>Assisted reproductive techniques or IVF</p> Signup and view all the answers

    How are dizygotic twins created?

    <p>After the ovulation of two oocytes, which are fertilized by two different sperms</p> Signup and view all the answers

    What is a characteristic of dizygotic twins?

    <p>They are genetically different</p> Signup and view all the answers

    How are the zygotes implanted in the uterus in dizygotic twins?

    <p>Separately in the uterus</p> Signup and view all the answers

    What is the likelihood of a woman conceiving fraternal twins if she is a fraternal twin?

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

    What is the result of the inner cell mass splitting in a blastocyst?

    <p>Two completely separate embryos with a common placenta and separate amniotic cavities</p> Signup and view all the answers

    What is the rare case of monozygotic twins?

    <p>Separation at the bilaminar germ disc stage</p> Signup and view all the answers

    What is the percentage of women who give birth to two babies when pregnant with twins?

    <p>29%</p> Signup and view all the answers

    What is the outcome of twin-twin transfusion syndrome?

    <p>Blood flow to one of the twins is more with poor outcome</p> Signup and view all the answers

    What are conjoined twins also known as?

    <p>Siamese twins</p> Signup and view all the answers

    What is the result of incomplete separation of the inner cell mass?

    <p>Conjoined twins</p> Signup and view all the answers

    What is the type of conjoined twins where bodies are fused from the upper chest to the lower chest?

    <p>Thoraco-omphalopagus</p> Signup and view all the answers

    What is the incidence of low birth rate in twins?

    <p>Higher than singletons</p> Signup and view all the answers

    What is the mortality rate of twins compared to singletons?

    <p>3 times higher</p> Signup and view all the answers

    What is the percentage of twins born preterm?

    <p>60%</p> Signup and view all the answers

    What occurs in dizygotic twins during implantation?

    <p>The zygote implants individually at distant sites in the uterus</p> Signup and view all the answers

    What is a characteristic of erythrocyte mosaicism in dizygotic twins?

    <p>Each twin has two types of red blood cells</p> Signup and view all the answers

    What is a characteristic of monozygotic twins?

    <p>They have exactly the same genetic information</p> Signup and view all the answers

    What is one way monozygotic twins can arise?

    <p>Subdivision and splitting of a single embryo</p> Signup and view all the answers

    What happens when the zygote splits at the two-cell stage in monozygotic twins?

    <p>Two separate embryos develop with separate placentas</p> Signup and view all the answers

    What is the arrangement of membranes in monozygotic twins that split at the two-cell stage?

    <p>Similar to dizygotic twins</p> Signup and view all the answers

    How can monozygotic twins be recognized?

    <p>By their strong resemblance in blood groups, fingerprints, sex, and external appearance</p> Signup and view all the answers

    At what stages can the zygote split to form monozygotic twins?

    <p>At various stages, including the two-cell stage and the blastocyst stage</p> Signup and view all the answers

    What is a characteristic of the implantation of dizygotic twins?

    <p>The two zygotes implant at distant sites</p> Signup and view all the answers

    What can occur when the walls of the chorionic sac fuse in dizygotic twins?

    <p>The two chorionic sacs fuse</p> Signup and view all the answers

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