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OB/GYN > Isoimmunizations and Multifetal gestations > Flashcards

Isoimmunizations and Multifetal gestations Flashcards

1
Q

What is alloimmunization (isoimmunization)?

A

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

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2
Q

What is on the A antigen? B?

A 
A = N-acetyl galactosamine
B = Galactosamine
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3
Q

What does it mean to be Rh +?

A

Have the big D antigen

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4
Q

What is the inheritance pattern of Rh?

A

AD

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5
Q

What percent of the population is Rh negative?

A

15%

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6
Q

When is Rh status a concern?

A

If mother is Rh negative, and fetus is Rh positive

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7
Q

How does Fetal anemia 2/2 Rh status occur?

A

IgG antibodies cross placenta, attacking RBCs

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8
Q

Which antibodies can cross the placenta?

A

IgG

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9
Q

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

A

30 days

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10
Q

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

A

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

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11
Q

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

A

Spleen

Jaundice, and kernicterus

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12
Q

What are the causes of RBC transfer?

A

-Abortion/ectopic
-Abdominal trauma
-

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13
Q

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

A

Amniocentesis
Cordocentesis
Chorionic villus sampling

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14
Q

Can a partial molar pregnancy cause RBC transfer?

A

yes

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15
Q

When are mothers screened for RH incompatibility?

A
  • At the 1st prenatal visit
  • 28 weeks
  • Postpartum
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16
Q

What is the indirect Coombs test?

A

Mix Rh+ cells with maternal serum,

anti-Rh Ab will adhere

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17
Q

What is the direct Coombs test?

A

Infants RBCs + coombs serum

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18
Q

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

A
  • Serial Abs q2-4 weeks

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

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19
Q

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

A

Significant risk for hydrops

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20
Q

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

A

When she has high levels of Ab against Rh +

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21
Q

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
A
  • ascites
  • pleural effusions
  • Skin edema
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22
Q

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

A

True

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23
Q

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

A

True

24
Q

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

A

Plots bili values and determines the risk to the fetus

Godd after 27 weeks

25
Q

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

A 
I = Very low risk
II = Mild to moderate
III = severe fetal anemia with high probability of death
26
Q

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

A

Blood flow is preserved to the brain

Not reliable after 35 weeks

27
Q

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

A

Near 100%

28
Q

What are the two treatment options for fetal anemia?

A
  • Intravascular fetal transfusion

- Preterm birth

29
Q

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

A

Watch for early jaundice

Cort DAT positive

30
Q

What is the treatment for HDN?

A
  • Bili lights

- Blood transfusion exchange

31
Q

What is RhoGAM?

A

Anti-D immunoglobulin

32
Q

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

A

Test to assess the percent of RBC in maternal circulation

Difference in acid elution rates between HbF and HbA allows for separation

33
Q

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

A

15 mL or 30 mL of whole blood

34
Q

What is the calculation to determine Fetal red cells?

A

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

35
Q

What is the incidence of multifetal gestation?

A

1 in 90

36
Q

What causes dizygotic twins?

A

Two separate ova fertilized by two separate sperm

37
Q

What causes monozygotic twins?

A

Division of a fertilized ovum after conception

38
Q

In whom are dizygotic twins common? (2)

A
  • Older mother

- Higher parity

39
Q

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

A

Division of the conceptus within 3 days of fertilization

40
Q

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

A

division occurs occurs between 4-8 days

41
Q

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

A

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

42
Q

What is the amnion?

A

The innermost membrane that encloses the embryo

43
Q

What is the chorion?

A

the outermost membrane surrounding an embryo

44
Q

What are the major issues with monoamniotic/monochorionic pregnancies?

A

Potential for cord ties and other issues

45
Q

When should you suspect twin pregnancies?

A

Size greater than dates on exam

46
Q

When can chorionicity be determined on US?

A

9-10 weeks

47
Q

What are the risks with multiple gestations? (4)

A
  • Anemia
  • Operative delivery
  • Discordant growth
  • Hydramnios
48
Q

What determines discordant growth in twins?

A

When one is 20% larger than the other

49
Q

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

A

Abnormal placentations

50
Q

Why is there a risk of postpartum hemorrhage with twins?

A

Distended uterus muscle has problem contracting

51
Q

What is twin-twin transfusion syndrome?

A

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

52
Q

What are the complications from twin-twin transfusion syndrome?

A
  • Impaired growth/anemia/hypovolemia in one

- Hypervolemia, HTN, polycythemia in the other

53
Q

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

A

Monochorionic

54
Q

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

A

Upon the presenting twin presentation

55
Q

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

A

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

56
Q

What is a double set up?

A

Having both c-section tools and vaginal birth tools ready

57
Q

How many teams are there for multiple fetuses?

A

As many kids as there are

OB/GYN (33 decks)

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