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Multifetal Gestation

All except which of the following complications are increased in multifetal gestations?

a. Preeclampsia

b. Hysterectomy

c. Maternal death

d. Postterm delivery

Which of the following mechanisms may result in monozygotic twins being discordant for malformations or traits?

a. Prezygotic mutation

b. Variable expression of the same genetic disease

c. Skewed lyonization in male fetuses with differential expression of X-linked traits or diseases

d. All of the above

A 37-year-old G1 comes to establish prenatal care with you after being discharged from her reproductive endocrinologist. This pregnancy was conceived via single embryo transfer in vitro fertilization. Which one of the following is true regarding her situation?

a. Assisted reproductive technology increases the incidence of monozygotic twins two- to fivefold.

b. If a single zygote splits 8 days post fertilization, a monochorionic diamnionic twin gestation results.

c. Because this pregnancy is known to have begun with one embryo, you can be certain that she will have monochorionic twins, but amnionicity depends on timing of split.

d. All of the above

A 29-year-old G1P1 conceived dichorionic twins via gonadotropin stimulation and intrauterine insemination (IUI) with her husband’s semen. Her blood type is O-negative, so prior to receiving anti-D immune globulin the neonates’ blood type is assessed. One neonate is A-positive and the other is O-negative. Her husband is A-positive. This finding can be explained to the parents by describing which of the following phenomena?

a. Superfetation

b. Superfecundation

c. This is not atypical for dichorionic twins

d. This cannot be explained without alleging infidelity or poor technique by her reproductive endocrinologist’s office.

The first trimester ultrasound image shown here shows two fetal heads arising from a shared body. How many days after fertilization must the division of this zygote have occurred to lead to the finding shown?

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