Twins

Question 1

Statistics

Answer 1

Multiple - 1.5% of all pregnancies
NND: 11.5/1000
MZ twins: 3.5/1000 
DZ varies with age, ethnicity, history
DZ - 80% of all twins (increased FSH = increased chance)

Question 2

Chorionicity

Answer 2

MC - share placenta - higher risk of mortality
DC - don’t share placenta
MA - share amniotic sac
DA - don’t share sac
Later division of egg for MZ twins - more likely to be MCMA

Question 3

Determination of chorionicity

Answer 3

• Lambda (DC) or T-sign (MC)
• Membrane thickness/layers (2.4mm+ DC)
• Composite measures (placental mass, sex, number of gest sacs)

Question 4

Antenatal care

Answer 4

11 week scan for chorionicity and DSS
Gest age based on bigger twin
If uncertain treat as MCDA

Question 5

Defects

Answer 5

Chr. - same as singletons but in DZ if one is then double the risk the other is
Structural - DC same as single. MC x2-3 and increased CHD
Double the risk when doing amnio for DC