Multiple Gestation Flashcards
Dizygotic twins are always…
- Dichorionic-diamniotic
Amnionicity and chorionicity of monozygotic twins is determined by…
- The timing of zygote cleavage
Cleavage days 1-4 results it…
- Diamniotic-dichorionic
Cleabage days 4-8 results in…
- Mnochorionic-diamniotic
Cleavage days 8-13 results in…
- Monochorionic-monoamniotic
Cleavage days 13-15 results it…
- Conjoined twins
All monochorionic twins are identical (T/F)
- True
Dichorionic twins are always dizygotic (T/F)
- False
Dizygotic twins are always dichorionic (T/F)
- True
Monochorionic twins may be dizygotic (T/F)
- False
Monoamniotic twins major issue is…
- Cord entanglement (all have it)
Spontaneous conception of twins
- 70% dizygotic/30% monozygotic
The monozygotic twin placentation is as follows:
- 34% diamniotic-dichorionic
- 65% monochorionic-diamniotic
- 1% monoamniotic-monochorionic
Most common monozygotic twin placentation
- Monochorionic-diamniotic
How are twin pregnancies diagnosed?
- Ultrasound; count the # of placentas
- Check gender
- Check for lambda (or chorionic peak sign) sign
- Check membrane thickness
Ultrasound method of diagnosing chorionicity/amnionicity
- Count # of placentas
- If 2 placentas = then DC
- If 1 placenta = then either DC or MC
Gender check method in diagnosing chorionicity/amnionicity
- If discordant genders, then DC
- If same gender, either DC or MC
Lambda sign method of diagnosing chorionicity/amnionicity
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
T-sign
- Line produced when 2 amnions meet
Membrane thickness check method in diagnosing chorionicity/amnionicity
- 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
Dichorionic-Diamniotic twins risks
- Fetal aneuploidy (33 yrs is Advanced Maternal Age)
- Delayed interval delivery
Dichorionic-Diamniotic Management
- Serial growth ultrasounds every 4-6wks
- Serial (usually weekly) nonstress testing during 3rd trimester
- Deliver by 38wks
Monochorionic-Diamniotic twins risks
- 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)
Monochorionic-Diamniotic twins management
- 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
Monoamniotic twins risks
- Cord entanglement-leading to fetal death
- 20-30% risk of neurologic impairment (cerebral palsy) of surviving twin after death of one twin
Monoamniotic twins management
- 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
Conjoined twins most frequent varieties
- Thoracopagus: 40-70%
- Omphalopagus: 10-33%
- Pygopagus: 18%
- Ischiopagus: 6%
- Craniopagus: 1-6%
Conjoined twins management
- Termination
- No surgery (unable to separate)
- Estensive multidisciplinary surgery to separate both twins, or salvage one
