Isoimmunizations and Multifetal gestations

Question 1

What is alloimmunization (isoimmunization)?

Answer 1

Immune response generated in an individual of one species, by an alloantigen from a different species

Question 2

What is on the A antigen? B?

Answer 2

A = N-acetyl galactosamine
B = Galactosamine

Question 3

What does it mean to be Rh +?

Answer 3

Have the big D antigen

Question 4

What is the inheritance pattern of Rh?

Answer 4

AD

Question 5

What percent of the population is Rh negative?

Answer 5

15%

Question 6

When is Rh status a concern?

Answer 6

If mother is Rh negative, and fetus is Rh positive

Question 7

How does Fetal anemia 2/2 Rh status occur?

Answer 7

IgG antibodies cross placenta, attacking RBCs

Question 8

Which antibodies can cross the placenta?

Answer 8

IgG

Question 9

When in gestation do the Rh antigens get expressed by baby?

Answer 9

30 days

Question 10

What is the significance of the 0.1 ml of blood the passes between mother and fetus during a normal delivery?

Answer 10

Not large enough to cause a response, but more than that and an immune response can take place

Question 11

Where do the RBCs in the fetal circulation get broken down at? What happens?

Answer 11

Spleen

Jaundice, and kernicterus

Question 12

What are the causes of RBC transfer?

Answer 12

-Abortion/ectopic
-Abdominal trauma
-

Question 13

What are the procedures that can cause RBC transfer? (3)

Answer 13

Amniocentesis
Cordocentesis
Chorionic villus sampling

Question 14

Can a partial molar pregnancy cause RBC transfer?

Answer 14

yes

Question 15

When are mothers screened for RH incompatibility?

Answer 15

• At the 1st prenatal visit
• 28 weeks
• Postpartum

Question 16

What is the indirect Coombs test?

Answer 16

Mix Rh+ cells with maternal serum,

anti-Rh Ab will adhere

Question 17

What is the direct Coombs test?

Answer 17

Infants RBCs + coombs serum

Question 18

How do you follow women who have antibodies to Rh +?

Answer 18

• Serial Abs q2-4 weeks

- If titre more than 1:16, then amniocentesis and increase 1-2 weeks

Question 19

What happens when the critical value of the Ab titer (for Rh) is hit?

Answer 19

Significant risk for hydrops

Question 20

When should amniocentesis never be performed on an Rh - woman?

Answer 20

When she has high levels of Ab against Rh +

Question 21

Which of the following US parameters is useful for determining the risk for fetal anemia 2/2 Rh antigen:

• skin edema
• Placental thickness
• Umbilical vein diameter
• Hepatic size
• Pleural effusions
• Splenic size
• Polyhydramnios
• Ascites

Answer 21

• ascites
• pleural effusions
• Skin edema

Question 22

True or false: the amount of bilirubin sampled in an amniocentesis correlates with the amount of fetal hemolysis

Answer 22

True

Question 23

True or false: you should avoid transplacental needle passage with amniocentesis

Answer 23

True

Question 24

What is the Liley curve, and what is it used for? When is this accurate?

Answer 24

Plots bili values and determines the risk to the fetus

Godd after 27 weeks

Question 25

What is the risk level for zones I-III on the liley curve?

Answer 25

``` I = Very low risk II = Mild to moderate III = severe fetal anemia with high probability of death ```

Question 26

Why is the middle cerebral artery flow dopplered instead of other arteries? When is this no longer reliable?

Answer 26

Blood flow is preserved to the brain Not reliable after 35 weeks

Question 27

What is the sensitivity of middle cerebral artery doppler in detecting severe anemia?

Answer 27

Near 100%

Question 28

What are the two treatment options for fetal anemia?

Answer 28

- Intravascular fetal transfusion | - Preterm birth

Question 29

How do you diagnose hemolytic disease of the newborn (HDN) after birth?

Answer 29

Watch for early jaundice | Cort DAT positive

Question 30

What is the treatment for HDN?

Answer 30

- Bili lights | - Blood transfusion exchange

Question 31

What is RhoGAM?

Answer 31

Anti-D immunoglobulin

Question 32

What is the Kleihauer-Betke test? How does this work?

Answer 32

Test to assess the percent of RBC in maternal circulation Difference in acid elution rates between HbF and HbA allows for separation

Question 33

300 mcg of Rhogam covers how many ml of fetal cells? Fetal Whole blood?

Answer 33

15 mL or 30 mL of whole blood

Question 34

What is the calculation to determine Fetal red cells?

Answer 34

MBV x Maternal HCT x%fetal cells in KB /newborn HCT

Question 35

What is the incidence of multifetal gestation?

Answer 35

1 in 90

Question 36

What causes dizygotic twins?

Answer 36

Two separate ova fertilized by two separate sperm

Question 37

What causes monozygotic twins?

Answer 37

Division of a fertilized ovum after conception

Question 38

In whom are dizygotic twins common? (2)

Answer 38

- Older mother | - Higher parity

Question 39

What is a diamniotic/dichorionic pregnancy? When does it occur?

Answer 39

Division of the conceptus within 3 days of fertilization

Question 40

What is a diamniotic/monochorionic pregnancy? When does it occur?

Answer 40

division occurs occurs between 4-8 days

Question 41

What is a monoamniotic/monochorionic pregnancy? When does it occur?

Answer 41

Division occurs between 9-12 days after development of both amnion and chorion

Question 42

What is the amnion?

Answer 42

The innermost membrane that encloses the embryo

Question 43

What is the chorion?

Answer 43

the outermost membrane surrounding an embryo

Question 44

What are the major issues with monoamniotic/monochorionic pregnancies?

Answer 44

Potential for cord ties and other issues

Question 45

When should you suspect twin pregnancies?

Answer 45

Size greater than dates on exam

Question 46

When can chorionicity be determined on US?

Answer 46

9-10 weeks

Question 47

What are the risks with multiple gestations? (4)

Answer 47

- Anemia - Operative delivery - Discordant growth - Hydramnios

Question 48

What determines discordant growth in twins?

Answer 48

When one is 20% larger than the other

Question 49

Why is there an increased risk for antepartum bleeding with twins?

Answer 49

Abnormal placentations

Question 50

Why is there a risk of postpartum hemorrhage with twins?

Answer 50

Distended uterus muscle has problem contracting

Question 51

What is twin-twin transfusion syndrome?

Answer 51

Monochorionic gestation, where AV anastomosis in the placental bed between the two fetal circulations, with one baby stealing blood from the other

Question 52

What are the complications from twin-twin transfusion syndrome?

Answer 52

- Impaired growth/anemia/hypovolemia in one | - Hypervolemia, HTN, polycythemia in the other

Question 53

In what type of pregnancies does twin-twin transfusion syndrome occur?

Answer 53

Monochorionic

Question 54

If twins are going to be delivered vaginally, what does this depend on?

Answer 54

Upon the presenting twin presentation

Question 55

Why is it better if the first twin delivered vaginally is biggest than the second?

Answer 55

Ensures that the second one will fit through, even if breech

Question 56

What is a double set up?

Answer 56

Having both c-section tools and vaginal birth tools ready

Question 57

How many teams are there for multiple fetuses?

Answer 57

As many kids as there are