Pathology of Twinning Flashcards
95% of twins from fertility treatments are ___________.
dizygotic
There are four kinds of monozygotic twins: ______________.
- Dichorionic diamnionic (division within 4 days of fertilization)
- Monochorionic diamnionic (division between 4-8 days after fertilization)
- Monochorionic monoamnionic (division between 8-12 days)
- Monochorionic monoamnionic conjoined twins (division after 13 days)
The most common type of monozygotic twins are ___________.
monochorionic dizygotic twins (70% of cases)
Looking at an ultrasound, how can you distinguish a mono/di from a di/di?
The di/di show the lambda sign (chorion and amnion) and the mono/di show the T sign (because of the thinner amnion).
Cord entanglement is a common problem in _____________.
monochorionic/monoamniotic
What are some risks of twin pregnancies?
- Miscarriage
- Hyperemesis
- Increased risk of aneuploidy and anomalies
- Diagnostic/screening protocols are less sensitive
- Anemia
- Diabetes
- Preeclampsia
- Preterm delivery
- Hemorrhage
- Growth restriction
- Perinatal mortality (5x-7x rate of single pregnancies)
When is a baby considered full-term?
37 weeks (even though most pregnancies are 40 weeks)
Perinatal mortality increases with ________________.
later division (meaning conjoined twins have the worst mortality followed by mono/mono twins)
What is twin-twin transfusion syndrome?
TTTS occurs in mono/di twins when anomalous blood connections develop across the amniotic sacs. One twin essentially gives their arterial blood to the other twin via the recipient’s veins.
The _________ twin in TTTS develops a larger bladder to reduce blood flow.
recipient
Arteries run ______ veins over the chorionic plate.
over
Why are mono/di twins at the highest risk for TTTS?
Dichorionic twins have two placentas and thus have very few (if any) anastomoses.
Monochorionic monoamnionic twins have so many connections that they likely balance out on the aggregate.
How has the incidence of twins changed recently?
It was 1:53 gestations in 1980; now it is 1:30.
The incidence of twinning is __________ in women using fertility treatment.
20x the spontaneous rate
Why does the donor twin in TTTS develop oligohydramnios?
Because the fetus decreases its urine production to increase blood volume.
