embryology of multiple gestations

Question 1

mono

di zygocity

chorionicity

amnionocity

Answer 1

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

Question 2

is there greater risk to muliple gestation?

Answer 2

yes for fetuses and mom risks of morbidity and morataily are significantly increased (7-10 x per HA)

Question 3

what increases odds of multiples?

Answer 3

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

Question 4

ethnic background and multiples

Answer 4

Question 5

dizygotic vs monozygotic

Answer 5

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.

Question 6

types of monozygotic twins

Answer 6

Question 7

of the different types of monozygotic twins which is the most common?

Answer 7

monochorionic/diamniotic make up 75%

Question 8

what type of tiwns are represented in this image?

Answer 8

dizygotic w/ separate placentas

Question 9

fyi

Question 10

what is the difference b/t these 2 gestations?

Answer 10

the first image is dichorionic and the second, monochorionic

Question 11

what is the timeline for a dichorionic/diamnionic pregnancy for dizyogotic twins?

Answer 11

first 3 days post conception when the zygote divides b/t the 2 cell stage and the morula.

Question 12

what can you say about this placenta?

Answer 12

it’s fused together. see below for separate

Question 13

what is the timeline for monochorionic/diamniotic pregnancy?

Answer 13

single zygote divides b/t days 4-8 in early blastocyst stage. results in shared placenta. (compare front pic to this di/di pic)

Question 14

what is the timeline for a monochorionic/monoamnionic pregnancy?

Answer 14

sincle blastocyst dividing after 8 days yielding 2 embroys from one inner cell mass

Question 15

what type of pregnancy is this?

Answer 15

dichorionic/diamnionic

Question 16

what types of prenancies are these? how can you tell?

Answer 16

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

Question 17

what type of pregnancy is this?

Answer 17

monochorionic/diamniotic *can’t tell be first image hence 2 image taken in different place. these are a few more mono-di images.

Question 18

what are the risks and complications w/ mono-mono pregnancies?

Answer 18

Premature rupture of membranes (PROM): Preterm labor
Intrauterine growth restriction (IUGR)
Pregnancy induced hypertension
Monochorionic twin syndromes

tangled umbilical cord (image)

Question 19

what kinds of limited fusion (limbs are separate) complications are there w/ conjoined twins?

Answer 19

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)

Question 20

what type of complication that are more extensive are there w/ conjoined tiwns?

Answer 20

Thoraco- omphalopagus
Thoracic & abdominal fusion

Question 21

what does this image show w/ regards to these conjoined twins?

Answer 21

they are conjoined at the abdomen (omphalopagus)

Large arrows show shared liver
Smaller arrows show fetal stomachs

Question 22

other types of multiples…

Answer 22

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.

Question 23

when imaging multiples remember…

Answer 23

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

Question 24

labeling multiples

Answer 24

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’

Question 25

documentation of multiples

Answer 25

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