Multiple Gestation

Question 1

Dizygotic twins are always…

Answer 1

• Dichorionic-diamniotic

Question 2

Amnionicity and chorionicity of monozygotic twins is determined by…

Answer 2

• The timing of zygote cleavage

Question 3

Cleavage days 1-4 results it…

Answer 3

• Diamniotic-dichorionic

Question 4

Cleabage days 4-8 results in…

Answer 4

• Mnochorionic-diamniotic

Question 5

Cleavage days 8-13 results in…

Answer 5

• Monochorionic-monoamniotic

Question 6

Cleavage days 13-15 results it…

Answer 6

• Conjoined twins

Question 7

All monochorionic twins are identical (T/F)

Answer 7

• True

Question 8

Dichorionic twins are always dizygotic (T/F)

Answer 8

• False

Question 9

Dizygotic twins are always dichorionic (T/F)

Answer 9

• True

Question 10

Monochorionic twins may be dizygotic (T/F)

Answer 10

• False

Question 11

Monoamniotic twins major issue is…

Answer 11

• Cord entanglement (all have it)

Question 12

Spontaneous conception of twins

Answer 12

• 70% dizygotic/30% monozygotic

The monozygotic twin placentation is as follows:

• 34% diamniotic-dichorionic
• 65% monochorionic-diamniotic
• 1% monoamniotic-monochorionic

Question 13

Most common monozygotic twin placentation

Answer 13

• Monochorionic-diamniotic

Question 14

How are twin pregnancies diagnosed?

Answer 14

• Ultrasound; count the # of placentas
• Check gender
• Check for lambda (or chorionic peak sign) sign
• Check membrane thickness

Question 15

Ultrasound method of diagnosing chorionicity/amnionicity

Answer 15

• Count # of placentas
• If 2 placentas = then DC
• If 1 placenta = then either DC or MC

Question 16

Gender check method in diagnosing chorionicity/amnionicity

Answer 16

• If discordant genders, then DC
• If same gender, either DC or MC

Question 17

Lambda sign method of diagnosing chorionicity/amnionicity

Answer 17

Lambda sign is the line where chorions meet

• If there is a lambda sign, probably DC

(Note: Lambda sign may disappear after 16wks)

• If no lambda sign, may be MC

Question 18

T-sign

Answer 18

• Line produced when 2 amnions meet

Question 19

Membrane thickness check method in diagnosing chorionicity/amnionicity

Answer 19

• DC membrane is thick (4 layers; 2 chorion, 2 amnion)

*usually easy to find

• MC membrane is thin (2 layers; both amnion)

*can be very difficult to find

• If its <2mm then it goes along with monochorionic-diamniotic twins
• If its >2mm then it goes along with dichorionic-diamniotic twins

Question 20

Dichorionic-Diamniotic twins risks

Answer 20

• Fetal aneuploidy (33 yrs is Advanced Maternal Age)
• Delayed interval delivery

Question 21

Dichorionic-Diamniotic Management

Answer 21

• Serial growth ultrasounds every 4-6wks
• Serial (usually weekly) nonstress testing during 3rd trimester
• Deliver by 38wks

Question 22

Monochorionic-Diamniotic twins risks

Answer 22

• Twin-to-Twin Transfusion Syndrome (TTTS)
• 20-30% risk of neurologic impairment (cerebral palsy) of surviving twin after death of one twin
• Twin-Reversed-Arterial Perfusion (TRAP)

Question 23

Monochorionic-Diamniotic twins management

Answer 23

• Serial ultrasound evals every 2wks to rule out twin-to-twin transfusion
• Serial ultrasound evals every 4wks to evaluate interval fetal twin growth
• Serial non-stress testing in third trimester
• Deliver by 34-36wks
• Invasive interventions to manage TTTS and TRAP

Question 24

Monoamniotic twins risks

Answer 24

• Cord entanglement-leading to fetal death
• 20-30% risk of neurologic impairment (cerebral palsy) of surviving twin after death of one twin

Question 25

Monoamniotic twins management

Answer 25

- Serial growth ultrasounds every 2-3wks - A min. of 4hrs of daily fetal non-stress testing from 24-32wks - Delivery at 32wks via cesarean section

Question 26

Conjoined twins most frequent varieties

Answer 26

- Thoracopagus: 40-70% - Omphalopagus: 10-33% - Pygopagus: 18% - Ischiopagus: 6% - Craniopagus: 1-6%

Question 27

Conjoined twins management

Answer 27

- Termination - No surgery (unable to separate) - Estensive multidisciplinary surgery to separate both twins, or salvage one