Multiple Gestation

Question 1

What is zygosity?

Answer 1

fertilization of # of eggs/ova

Question 2

What is monozygotic?

Answer 2

one zygote [ova/sperm] that divides into two separate individuals. “Identical twins”

Question 3

What is dizygotic?

Answer 3

twins resulting from fertilization of two ova and two sperm. Not genetically identical

Question 4

What is chorionicity?

Answer 4

the number of chorionic (outer) membranes surrounding the fetus

Question 5

What is amnionicity?

Answer 5

the number of amnionic (inner) membranes that surround fetuses in a multiple pregnancy

Question 6

What percentage of twins are monozygotic?

Answer 6

~30%

Question 7

What percentage of twins are dizygotic?

Answer 7

~70%

Question 8

What percentage of all live births are multiples?

Answer 8

3%

Question 9

Can monozygotic twins have dichorionic membranes?

Answer 9

yes

Question 10

Can dizygotic twins have a monochorionic membrane?

Answer 10

no

Question 11

What plays a key role in if monozygotic will have monochorionic or dichorionic membranes?

Answer 11

timing of division

Question 12

Can monozygotic twins be monoamniotic?

Answer 12

yes

Question 13

Can dizygotic twins be monoamniotic?

Answer 13

no

Question 14

What is another name for monoamniotic twins?

Answer 14

mono-mono twins

Question 15

What percentage of monozygotic twins are mono-mono?

Answer 15

1%

Question 16

What is the mortality rate of mono-mono twins?

Answer 16

50-60%

Question 17

What is a large reason that there is such a high mortality rate for mono-mono twins?

Answer 17

umbilical cords may become entangled

Question 18

Why may some dizygotic twins look like they share a placenta?

Answer 18

Placentas may fuse. This does not make them monochorionic!!

Question 19

When is it more likely that monozygotic twins will share a chorion?

Answer 19

If the twins divide later in gestation

Question 20

How many days will monozygotic twins have to divide before running the risk of becoming conjoined?

Answer 20

13-18 days

Question 21

If monozygotic twins divide in 1-3 days, what type of amnion and chorion will they most likely have?

Answer 21

dichorion and diamnion

Question 22

What are di-di twins?

Answer 22

two chorions and two amnions

Question 23

If one twin is receiving more blood than the other, which twin has a higher morbidity rate?

Answer 23

the twin that has too much blood

Question 24

What will confirm multiple gestation?

Answer 24

ultrasound

Question 25

If babies are di-di, can they share a placenta?

Answer 25

no