LC Exam 2: Twinning

Question 1

Types of twinning

Answer 1

Dizygotic (fraternal) 2/3
Monozygotic (identical) 1/3
Mono or diamniotic

Question 2

0-4 split

Answer 2

Dichorinoic diamniotic (monozygotic)
Also: 2 eggs/2sperm = dichorionic diamniotic (but dizygotic)

Question 3

4-8 split

Answer 3

Monochorionic diamniotic (monozygotic, ~70%)
1 trophoblast
2 inner cell masses

Question 4

8-12 split

Answer 4

Monochorionic monoamniotic (monozygotic)

Question 5

> 13 split

Answer 5

Monochornic monoamniotic, conjoined (monozygotic)

Question 6

Determining chorionicity

Answer 6

Thick separating membrane = Di/Di (contains chorion)
Lambda sign (peaked dividing) = Di/Di
Thin separating membrane = Mo/Di (no chorion, only two amnions)
T sign (90˚ dividing) = Mo/Di

Question 7

Does Molly like tacos?

Answer 7

Does a bear shit in the woods?

Question 8

Risks of twin pregnancies

Answer 8

Higher risk of miscarriage
Hyperemesis (increased ßhCG)
Higher risk of aneuplodies
Anemia
Gestational diabetes (increased hPL)
Gestational HTN/preeclampsia
Screening tests and diagnostic procedures harder
INCREASED COMPLICATIONS WITH MORE MO

Question 9

Twin-twin transfusion syndrome

Answer 9

Occurs in Mo/Di
Unbalanced flow in vessels
Recipient twin: large, polyhydramnios
Donor twin: small, oligohydramnios
A-V connections lead to unbalanced flow (more likely in Mo/Di)
A-A and V-V connections are less worrisome

Question 10

TTTS untreated prognosis

Answer 10

80-90% mortality untreated
Mortality of one leads to 1/3 brain damage in other
Donor: low volume, low nutrient
Recipient: overload, HF

Question 11

TTTS treatment

Answer 11

Repeat US and follow up
Laser ablation (even with demise of one twin still use)
Reduction amniocentesis from recipient (early delivery risk)
Microseptostomy: creation of hole to equalize

Question 12

Monochorionic monoamniotic complications

Answer 12

Tangling of cords, common/fatal complication