Flashcards in Twins Deck (14):
What is the optimal time to determine chorionicity in a twin pregnancy?
What cut-offs are used to diagnose discordant growth of twins?
difference in EFW > 20%
difference in AC > 20 mm
At what gestational age should twins be delivered:
M/M: 32-33 weeks
M/D: 36-37 weeks
DC: 37-38 weeks
List three reasons why perinatal morbidity & mortality is higher with twin pregnancies compared with singletons.
- PTB, PPROM
- IUGR, HDP
- Congenital anomalies
- Twin-specific problems such as TTTS
Distinguish between monozygotic and monochorionic twins.
Monozygotic: "identical twins," egg + sperm = single zygote which splits to produce twins
Monochorionic: obligately monozygotic, single shared placenta
List four items on the differential diagnosis for increased SFH.
Adnexal or abdominal mass
List five factors which increase the rate of twinning, and specify whether these factors increase rates of monozygotic twinning, dizygotic twinning, or both.
Increased maternal age
Family history of twins (maternal > paternal)
Elevated levels of pituitary gonadotropins
Infertility, ART use
(Only use of ART increases the rate of monozygotic twinning - rate is otherwise constant at 1 in 250 births)
Distinguish between the placental anastomoses responsible for TTTS & TRAP.
TTTS - arteriovenous anastomoses
TRAP - arterioarteriolar anastomoses
Describe the Quintero stages of TTTS.
1 - poly/oli
2 - poly/oli plus absent bladder in donor twin
3 - poly/oli, absent bladder, plus abnormal Dopplers
4 - ascites or hydrops in either twin
5 - demise of either twin
Which of the following therapies has evidence for reducing preterm delivery in twin pregnancies:
In a twin dating ultrasound, which CRL should be used to establish the due date, and why?
Larger twin - no good evidence but this is the conservative option in that it reduces the chance of missing IUGR later on
List three ways twin chorionicity & amnionicity can be determined prior to and after 10 weeks' gestation.
Before 10 weeks: number of gestational sacs (each forms its own chorion), number of amniotic sacs, number of yolk sacs (each is associated with a single amnion)
After 10 weeks:fetal genitalia, placental number, chorionic peak sign (lambda or T sign), inter-twin membrane thickness (2 mm threshold for chorionicity), cord or limb entanglement
What specific kind of fetal anomalies are most common in twins & why?
Midline structural defects - resulting from the twinning process in monozygotic twins
(Frequency of congenital anomalies not thought to be increased in dizygotic twins)