embryology of multiple gestations Flashcards
mono
di zygocity
chorionicity
amnionocity
Mono -Means one
Di - Means two
Zygocity- Number of fertilized ovum/ova. Monozygotic or dizygotic
Chorionicity – Number of placentas
Monochorionic or dichorionic
Amnionicity – Number of amniotic sacs
Monoamniotic or diamniotic
is there greater risk to muliple gestation?
yes for fetuses and mom risks of morbidity and morataily are significantly increased (7-10 x per HA)
what increases odds of multiples?
Heredity –Dizygotic twinning increases with a family history of twins because of multiple ovulation
Advancing maternal age (peak at 35-39 years)
Assisted reproductive technology (ART)
Ovulation induction agents – Example polycystic ovarian syndrome (PCOS) patients
Previous twin gestation
Increasing parity
Social class – Twinning decreases with undernourishment
ethnic background and multiples
dizygotic vs monozygotic
dizygotic makes up 2/3 of twin pregnancies. these aer the twins that orginate from 2 fertilized ova by 2 sperm aka fraternal twins resulting in the implantation of 2 blastocysts which will be dichorionic and diamniotic.
monozygotic make up the other 1/3 of twin pregnancies. these twins originate from 1 single fertilized ovum aka identical twins. they have variations in the chorion and amnion (can be di or mono) and the placenta which can be seaparate or fused.
types of monozygotic twins
of the different types of monozygotic twins which is the most common?
monochorionic/diamniotic make up 75%
what type of tiwns are represented in this image?
dizygotic w/ separate placentas
fyi
what is the difference b/t these 2 gestations?
the first image is dichorionic and the second, monochorionic
what is the timeline for a dichorionic/diamnionic pregnancy for dizyogotic twins?
first 3 days post conception when the zygote divides b/t the 2 cell stage and the morula.
what can you say about this placenta?
it’s fused together. see below for separate
what is the timeline for monochorionic/diamniotic pregnancy?
single zygote divides b/t days 4-8 in early blastocyst stage. results in shared placenta. (compare front pic to this di/di pic)
what is the timeline for a monochorionic/monoamnionic pregnancy?
sincle blastocyst dividing after 8 days yielding 2 embroys from one inner cell mass
what type of pregnancy is this?
dichorionic/diamnionic
what types of prenancies are these? how can you tell?
1st is dichorionic/diamnionic b/c of thick wall separating the 2. the 2nd image is monchorionic/diamnionic b/c of the thin wall separation
what type of pregnancy is this?
monochorionic/diamniotic *can’t tell be first image hence 2 image taken in different place. these are a few more mono-di images.
what are the risks and complications w/ mono-mono pregnancies?
Premature rupture of membranes (PROM): Preterm labor
Intrauterine growth restriction (IUGR)
Pregnancy induced hypertension
Monochorionic twin syndromes
tangled umbilical cord (image)
what kinds of limited fusion (limbs are separate) complications are there w/ conjoined twins?
Craniopagus -Joined at the head (ex. A, B &C)
Thoracopagus - Thoracic fusion (ex. D to G)
Omphalopagus - Joined from umbilicus to xiphoid cartilage
Pygopagus -Joined by posterolateral sacrum & coccyx (ex. H)
Ischiopagus - Joined by inferior sacrum & coccyx (ex. I)
what type of complication that are more extensive are there w/ conjoined tiwns?
Thoraco- omphalopagus
Thoracic & abdominal fusion
what does this image show w/ regards to these conjoined twins?
they are conjoined at the abdomen (omphalopagus)
Large arrows show shared liver
Smaller arrows show fetal stomachs
other types of multiples…
Triplets may occur from
1 zygote & be identical
2 zygotes & consist of identical twins & a singleton
3 zygotes & be of the same sex or of different sexes
Similar combinations occur in quadruplets, quintuplets, sextuplets & septuplets etc.
when imaging multiples remember…
Every OB US exam begins with scanning the uterus in longitudinal & transverse from one side to the other to determine the number of fetuses
Each fetus gets a completely separate exam
Do one fetus completely before going to the other/s –Avoids oversights
labeling multiples
Require additional terms to keep each embryo/fetus identified as separate
Fetus with the lowest presenting part should be labeled ‘A’
Examples: Twin A, Twin B
Fetus A, Fetus B, Fetus C, Fetus D etc.
If 2 fetuses coexist at the same level, label ‘left fetus’ or ‘right fetus’
documentation of multiples
Both heads on one image and both bodies on another, if possible, to prove that it is a multiple gestation and they are not conjoined
Membranes and their location
Number of placentas & their location
