Multiples & TTTS

Question 1

Define monozygotic twins

Answer 1

Resulting from one ovum fertilized by one sperm that splits into separate embryos

Question 2

Define dizygotic twins

Answer 2

Resulting from two ova fertilized by two separate sperm

Question 3

What are “di-di” twins

Answer 3

Diamniotic-dichorionic twins - having separate amnions and chorions and no shared blood vessels

Dizygotic twins are always di-di

Question 4

Describe “mo-mo” twins

Answer 4

Monoamniotic-monichorionic twins share the same amnion and chorion (placenta and sac)

Results from splitting between day 8-13

Less than 2% of monozygotic twins

Question 5

What causes twin-to-twin transfusion syndrome (TTTS)

Answer 5

Occurs when abnormal blood vessel connections in a shared placenta cause unequal blood flow between twins

Question 6

What are the key differences between chronic and acute TTTS?

Answer 6

Chronic - between 12-26 weeks, leading to extreme prematurity

Acute - occurs suddenly due to BP differences, often during labor or the third trimester

Question 7

What are the risks for the donor twin in TTTS?

Answer 7

Growth restriction, oligohydramnios, hypoplastic lungs, disappearance of bladder, death

Question 8

What are the risks for the recipient twin in TTTS?

Answer 8

Heart failure, polyhydramnios, hydrops, death

Question 9

What is the survival rate of untreated TTTS?

Answer 9

TTTS left untreated is lethal 70-100% of the time

Question 10

What are the treatment options for TTTS?
LA

Answer 10

Laser ablation of shared blood vessels
Amniotic fluid reduction

Question 11

What is a vanishing twin?

Answer 11

A phenomenon where one twin is reabsorbed, occurs in 3.3% of pregnancies and 36% of twin pregnancies before 7 weeks.

Question 12

What complications can arise from the late death of one twin?
DIPS

Answer 12

Death
Increased risk of cerebral palsy for the surviving twin
Premature birth
Severe hypotension due to blood loss

Question 13

Define “di-mo twins”.

Answer 13

Diamnionic-monichorionic twins share a placenta (chorion) but have their own sac (amnion)

Occurs when cell division happens between day 3-8

Approximately 65% of monozygotic twins are “di-mo”

Question 14

Conjoined twins result from what zygocity?

Answer 14

Monozygotic - occurs when split occurs after 13th day of conception

Question 15

Where is the most common place for conjoined twins to be “fused”

Answer 15

Thorapagus (chest wall) 35-40%

Omphalopagus (lower breast bone to waist) 34%

Question 16

What are maternal complications for carrying multiples?
A CHOPPP

Answer 16

Anemia

Cholestasis
Hyperemesis
Operative delivery
Pre-eclampsia
Pyelonephritis
Post partum hemorrhage

Question 17

What are potential congenital anomalies that are at an increased risk in the pregnancy of multiples?

Answer 17

Chromosome abnormalities
Cardiac abnormalities
Neural tube defects
TTTS
IVH

Question 18

What are fetal risks of multiple gestation?

Answer 18

Loss of one
Late fetal demise
cord accidents (monochoirionic)
IUGR/discordant growth
Cord prolapse
Malpresentation
Prematurity

Question 19

Define the qualifications for a TTTS diagnosis

Answer 19

One twin has to have 2 cm or less of fluid (donor) and
other has 8 cm or more of fluid (recipient) SIMULTANEOUSLY

Question 20

Define TTTS stage 1

Answer 20

Only fluid difference noted, no other factors

Question 21

Define TTTS stage 2

Answer 21

No visible bladder in donor twin

At this stage there is a 80-90% chance of loss of one or both twins

Question 22

Define TTTS stage 3

Answer 22

Signs of strain on the recipient twins heart

Question 23

Define TTTS stage 4
H&H

Answer 23

Heart failure in the recipient - hydrops develops
Hydrops and heart failure

Question 24

Define TTTS stage 5

Answer 24

One of the fetuses have died

Question 25

Which twin in TTTS is usually sicker initially?

Answer 25

Recipient - need cardiovascular support, manage excess fluid

Question 26

What are potential treatments for the donor twin in TTTS?

Answer 26

Correction of anemia, follow renal output, provide respiratory support, cranial ultrasound