Multiple Pregnancy

Question 1

What percentage of twin pregnancies are dizygotic?

Answer 1

70%

Question 2

What is the chorionicity and amnionicity of dizygotic twins?

Answer 2

They are dichorionic (have a placenta per twin) and diamniotic (have its own amniotic membrane)

Question 3

How does the age of splitting of monozygotic twins affect their chorionicity and amnionicity?

Answer 3

IF BEFORE 8 CELL STAGE (day 3) placenta and amnion will develop separately = DICHORIONIC and DIAMNIOTIC

SPLITTING AT BLASTOCYST STAGE (4-8 days) 
MONOCHORIONIC DIAMNIOTIC (most common)

SPLITTING AT 8-14 days = MONOCHORIONIC MONOAMNIOTIC

SPLITTING >14 DAYS - usually result in conjoined twins

Question 4

What are some maternal complications associated with multiple pregnancies?

Answer 4

Hyperemesis - increased hCG levels
Anaemia - more likely - further haemodiltuion d/t increased plasma
APH - placenta praevia and abruption both more likely
Pre-Eclampsia - 3-4X more likely in multiple pregnancies

Question 5

What are some fetal complications associated with multiple pregnancies?

Answer 5

Structural anomalies much more common with MONOCHORIONICITY (cardiac and neural tube defects most common)
Chromosomal abnormality
Premature birth (typically 37-38 weeks) - again more common in monochorionic
IUGR (growth slows after 28-30w)
Twins with one fetal death
TTTS (twin-twin transfusion syndrome)

Question 6

What is TTTS? What are the risks? How is it managed?

Answer 6

Twin-Twin Transfusion Syndrome.
Net blood flow from one twin to the other due to aterio-venous anastomoses in the placenta
FOR RECIPIENT TWIN: hyperdynamic circulation with risk of cardiac failure and polyhydramnios
FOR DONOR TWIN: oliguria and oligohydramnios

80% pregnancy loss rate without treatment

Amniotic fluid drainage and laser ablation of anastomoses have both been shown to be useful

Question 7

How do we manage multiple pregnancies?

Answer 7

Determine chorionicity early - hard to do as foetuses get bigger
Counsel parents - sometimes twin doesn’t survive
Give additional visits depending on chorionicity
Monitor for complications (pre-eclampsia, anaemia)
Discuss delivery options at 32 weeks

Question 8

What additional visits will women with multiple pregnancies have?

Answer 8

MONOCHORIONIC

• every 2 weeks from 16-24w to monitor for TTTS
• detailed structural scan at 18 weeks
• Detailed fetal cardiac scan at 20-22
• Every 2 weals from 24 weeks for fetal growth assessment

DICHORIONIC

• Detailed structural survey at 18w
• Every 2 weeks from 24 weeks for fetal growth assessment