Multiple Gestation Flashcards
What is zygosity?
fertilization of # of eggs/ova
What is monozygotic?
one zygote [ova/sperm] that divides into two separate individuals. “Identical twins”
What is dizygotic?
twins resulting from fertilization of two ova and two sperm. Not genetically identical
What is chorionicity?
the number of chorionic (outer) membranes surrounding the fetus
What is amnionicity?
the number of amnionic (inner) membranes that surround fetuses in a multiple pregnancy
What percentage of twins are monozygotic?
~30%
What percentage of twins are dizygotic?
~70%
What percentage of all live births are multiples?
3%
Can monozygotic twins have dichorionic membranes?
yes
Can dizygotic twins have a monochorionic membrane?
no
What plays a key role in if monozygotic will have monochorionic or dichorionic membranes?
timing of division
Can monozygotic twins be monoamniotic?
yes
Can dizygotic twins be monoamniotic?
no
What is another name for monoamniotic twins?
mono-mono twins
What percentage of monozygotic twins are mono-mono?
1%
What is the mortality rate of mono-mono twins?
50-60%
What is a large reason that there is such a high mortality rate for mono-mono twins?
umbilical cords may become entangled
Why may some dizygotic twins look like they share a placenta?
Placentas may fuse. This does not make them monochorionic!!
When is it more likely that monozygotic twins will share a chorion?
If the twins divide later in gestation
How many days will monozygotic twins have to divide before running the risk of becoming conjoined?
13-18 days
If monozygotic twins divide in 1-3 days, what type of amnion and chorion will they most likely have?
dichorion and diamnion
What are di-di twins?
two chorions and two amnions
If one twin is receiving more blood than the other, which twin has a higher morbidity rate?
the twin that has too much blood
What will confirm multiple gestation?
ultrasound
