Multifetal Gestation and Malpresentation (Moulton) Flashcards
__1__ arise when two separate ova are fertilized by two separate sperm.
Each will have its own __2__, __2__, and __2__.
1) Dizygotic twins (Fraternal)
2) Amnion, chorion and placenta
__1__ arise from the cleavage of a single fertilized ovum at various stages during embryogenesis.
Thus the arrangement of __2__ and __2__ will depend on the time at which the embryo divides.
1) Monozygotic Twinning (Identical)
2) Fetal membranes and placentas
With Monozygotic twins, if cleavage takes place from 0-3 days, what happens with placentation? (30% of monozygotic twins have this placentation)
1) 2 chorions
2) 2 amnions
3) Placentas can be separate or fused
With Monozygotic twins, if cleavage takes place from 4-8 days, what happens with placentation? (69% of monozygotic twins have this placentation)
1) 1 chorion
2) 2 amnions
With Monozygotic twins, if cleavage takes place from 9-12 days, what happens with placentation? (1% of monozygotic twins have this placentation)
1) 1 chorion
2) 1 amnion
Monochorionic monoamniotic placentation (9-12 days) is the most dangerous because there are no separating amnions, this causes what risk to be high?
Cord entanglement is high
With Monozygotic twins, if cleavage takes place from 13-15 days, what happens with placentation?
This causes conjoined twins and if they are craniopagus (2% incidence) this means?
If they are thoracopagus (30-40% incidence)?
If they are ischiopagus (6% incidence)?
1) 1 chorion and 1 amnion
2) Joined at the cranium
3) Joined at the chest wall
4) Joined by the coccyx and sacrum
Dizygotic twins is strongly influenced by?
It is twice as common after?
1) Maternal age
2) 35 y/o
You should suspect multiple gestations if ___ is higher than normal.
hCG
When using US when determining zygosity for dizygotic twins you might see a different __1__ amongst the twins.
There may be visualization of a __2__ septum.
A __3__ sign at the base of septum may be seen.
1) Fetal gender
2) Thick amnion-chorion septum
3) Peak or inverted V
When using US when determining zygosity for monozygotic twins what may be seen?
Dividing membrane is thin
If ultrasound is not definitive in determining zygosity, what should you do?
1) Inspect placenta after delivery
2) DNA analysis
Conjoined twins results do to cleavage occurring at?
13-15 days
What presentation occurs 40-50% of the time for twins?
Vertex-vertex
__1__ and __1__ presentations can be delivered vaginally but often are delivered by cesarean section.
__2__ and __2__ twins are delivered via cesarean section.
1) Vertex-transverse and vertex-breech
2) Breech-breech and breech-vertex