Twins

Question 1

What are clinical associations for a twin pregnancy?

Answer 1

Large for gestational age (LGA), multiple heartbeats, SMAFP levels at > 2.5 MOM (multiple of median)

Question 2

What are the membrane configurations with twins?

Answer 2

Chorionic and amniotic

Question 3

What is dizygotic twinning?

Answer 3

The fertilization of 2 ovum (dichorionic/diamniotic)

Question 4

What is dizygotic twinning influenced by?

Answer 4

Genetics, environment, age and ART

Question 5

What is monozygotic twinning?

Answer 5

A random event resulting in single ovum division

Question 6

What are placental and membrane configurations with monozygotic twins?

Answer 6

Varies and has membrane configurations of: Di/Di, Mono/Di, and Mono/Mono

Question 7

What is the sonographic assessment for twins?

Answer 7

Fetal lie/number, # placentas, membranes? standard anatomy (biometry), AF - MVP (maximal vertical pocket), pulsed/color doppler

Question 8

Which type of pregnancy has an increased rate of obstetric complications?

Answer 8

Monochorionic

Question 9

What is dichorionic/diamniotic comprised of?

Answer 9

2 layers of chorion, 2 layers of amnion

Question 10

How does Di/Di appear on ultrasound in the first trimester?

Answer 10

A thick echogenic layer of chorion surrounding each embryo

Question 11

How does Di/Di appear on ultrasound in the 2nd/3rd trimester?

Answer 11

2 placentas, twin peak/lambda sign

Question 12

How does the twin peak/lamda sign appear on ultrasound?

Answer 12

A wedge shape of chorionic tissue going into the base of the thick inter-twin membrane

Question 13

What happens with the amnion after 14-16 weeks?

Answer 13

It’s no longer seen separate from the chorion

Question 14

How does Mono/Di appear in the 1st trimester?

Answer 14

2 yolk sacs, embryos within same chorionic sac

Question 15

How does Mono/Di appear in the 2nd/3rd trimester?

Answer 15

Thin inter-twin membrane, no twin peak sign, one placenta, same gender

Question 16

What are the risks of Mono/Di pregnancy?

Answer 16

Twin-twin transfusion, evaluation of cord insertion for each twin

Question 17

How does Mono/Mono pregnancy appear?

Answer 17

1 chorionic layer, 1 amniotic layer and 1 placenta

Question 18

What is the majority problem with Mono/Mono pregnancy?

Answer 18

Cord entanglement (evaluate w/doppler)

Question 19

How does Mono/Mono appear in 1st trimester?

Answer 19

2 embryos with 1 yolk sac (after 7 weeks)

Question 20

How does Mono/Mono appear in 2nd/3rd trimester?

Answer 20

Same gender/no inter-twin membrane

Question 21

What causes vanishing twin?

Answer 21

Spontaneous abortion, embryonic malformation, nonviable pregnancy (20%)

Question 22

What is fetus papiraceus?

Answer 22

Death/preserved fetus due to compression

Question 23

What are maternal complications from fetus papiraceus?

Answer 23

Increased mortality/cesarian, hypertension, postpartum hemorrhage

Question 24

What are fetal complications from fetus papiraceus?

Answer 24

Low birth weight, congenital anomalies, vasa previa (overlying cervix, into amniotic membrane)

Question 25

What is twin reversed arterial perfusion (acardiac twinning)?

Answer 25

An acardiac twin dependent on other (pump twin)

Question 26

What happens in the placenta with acardiac twinning?

Answer 26

Anastomoses of arterial to arterial and venous to venous systems

Question 27

What are sonographic findings in acardiac twinning?

Answer 27

Possible hydrops (pump twin), malformed fetus w/no cardiac structures and flow reversal in cord (acardiac twin)

Question 28

What is twin to twin transfusion syndrome?

Answer 28

Blood shunting from arterial/venous anastomoses in shared placenta causing a perfusion imbalance between fetuses

Question 29

Which type of pregnancy may have twin to twin transfusion syndrome?

Answer 29

Monochorionic and diamniotic

Question 30

What are the amniotic fluid discrepancies in twin to twin transfusion syndrome?

Answer 30

Recipient twin has polyhydramnios, the donor twin has oligohydramnios

Question 31

What happens to the donor twin with twin to twin transfusion syndrome?

Answer 31

Growth restriction, hypovolemic (dilated cardiomyopathy/pericardial effusion) and anemia

Question 32

What happens to the recipient twin with twin to twin transfusion syndrome?

Answer 32

Macrosomic, hypervolemic (cardiomegaly, biventricular hypertrophy, tricuspid regurgitation) plethoric (red-faced) and possible hydrops

Question 33

What are sonographic diagnoses for twin to twin transfusion syndrome?

Answer 33

Single placenta, same-sex, fluid volume discrepancy, and 20% weight difference

Question 34

What type are the majority of conjoined twins?

Answer 34

Thoracopagus (thorax) and omphalopagus (abdominal wall) mostly female

Question 35

What are conjoined twins the result of?

Answer 35

Late monozygotic division (mono/mono) after day 13

Question 36

What must be differentiated with parasitic twin (fetus in fetu)?

Answer 36

Teratoma (malignancy) upper abdomen, | hemartoma (benign) lower abdomen

Question 37

What occurs with selective reduction in Di/Di pregnancies?

Answer 37

Termination with multiples or birth defects by injecting potassium chloride into fetal heart or umbilical cord