Obstetrics Study Sheet

Diagnostic Medical Sonography Program
Obstetrics/Multiple Pregnancies Study Sheet
By: Harry H. Holdorf

  • The following twin abnormality demonstrates a venous-to-venous anastomosis: Acardiac twin
    Acardiac twins shunt blood from the vein of one twin to the other or from one artery to the other. Twin-twin transfusion demonstrated an arteriovenous anastomosis.
  • A Monochorionic twin pregnancy in which one develops without an upper body is termed: Acardiac twin
    Acardiac twin is a rate anomaly of a monozygotic pregnancy. The Acardiac twin demonstrates a poorly developed upper body and an absent or rudimentary heart and receives blood through the normal twin gestation.
  • A Dizygotic gestation is expected to be: Dichorionic/diamniotic
    Two zygotes will always demonstrate dichorionic/diamniotic gestational sacs.
  • Twin gestation arising from two separate fertilized ova is termed: Dizygotic twins
    Fraternal or Dizygotic twins arise from separate ova that are individually fertilized.
  • This sonographic finding confirms the presence of a diamniotic pregnancy: Two gestational sacs
    Two individual amnions will demonstrate two separate gestational sacs. Monoamniotic pregnancies can demonstrate two Allantoic ducts, yolk sacs, and embryos. Dichorionic pregnancies will demonstrate two individual placentas.
  • With twin-twin transfusion syndrome, the recipient twin is likely to acquire: Hydrops Fetalis
    The recipient twin receives too much blood and may acquire hydrops Fetalis, placenta-megaly, and Polyhydramnios. The donor twin may display IUGR and Oligohydramnios.
  • Arteriovenous shunting within the placenta occurs with: Twin-twin transfusion
    In twin-twin transfusion the arterial blood of the donor twin shunts into the venous system of the recipient twin.
  • Which of the following is likely to occur if a single zygote divides 7 days after fertilization? Two amnion and one chorion
    Division of the zygote 4 to 8 days after fertilization will demonstrate two amnions (two gestational sacs) and one chorion (one shared placenta)
  • When a membrane is present between two fetuses in seen on a first trimester sonogram, this demonstrates: Diamniotic twins
    A membrane is present between the two fetuses (diamniotic). It is too early to determine placenta number and location (dichorionic).
  • A patient presents for an early second-trimester sonogram. A cross-sectional image reveals two fetal abdomens that appear to be joined.  This image is most suspicious for: Conjoined twins
    When the anterior abdominal walls of a twin pregnancy are conjoined is termed Conjoined twins. When an image is at the abdominal level, diagnosis of Acardiac twin is not possible.
  • What percentage of twin gestations will generally result in a singleton pregnancy at term? 70%
  • Which of the following most accurately describes twin-twin transfusion? Arterial blood from the donor twin is pumped into the venous system of the receiving twin
    In twin-twin transfusion, arterial blood from the donor twin pumps into the venous system of the receiving twin.
  • Fetal papyraceus is a term used to describe: Demise of a twin too large to resolve
  • Twin-twin transfusion generally demonstrates: Minimum fetal weight discordance of 20%
    A fetal weight discordance of > or equal to 20% defines Twin-twin transfusion. The donor twin may display Oligohydramnios and IUGR while the receiving twin may display Polyhydramnios and fetal hydrops.
  • Monozygotic twins are referred to as Identical twins because they arise form a single fertilized ovum, and are always the same gender.
  • Dizygotic or fraternal twins occur when two ova are fertilized by two sperm. Dizygotic twins comprise about two thirds of all twins.
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