Alloimmunization

Question 1

MoA of Alloimmunization

Antigen origin? Antibody origin?

Answer 1

Maternal antibodies made in response to presence of fetal antigen -> cross placenta in next pregnancy and attack fetus

occurs during blood-mixing

Question 2

What type of antibodies cause alloimmunization

and why?

production timing

Answer 2

IgG

(In constrast, IgM pentamers are hugeee)

because smaller, and can cross placenta

chronic!

Question 3

Lewis Antibodies

Hemolytic D/z Newborn?

Y/N?

Answer 3

No!

IgM Antibodies (Lewis Lives)

Question 4

Kell Antibodies

Hemolytic D/Z Newborn?

Y/N?

Answer 4

Yes

(capital) K = Kills; mild - severe fetal anemia

Question 5

Name the Rhesus Blood Group Antigens

Answer 5

D, C, c, E, and e

no little d

Question 6

Critical Titer for MCA Doppler Screening?

Answer 6

1:8

some are titer-dependent (i.e. Kell because it’s real evil)

Question 7

Rh-incompatibility incidence (ethnicity, race):
-highest
-lowest

Answer 7

Highest: White
Lowest: Asian, Native American

Question 8

Most common time for fetomaternal hemorrhage to cause alloimmunization

Answer 8

Delivery

Question 9

Min. amount of fetal blood needed to cause alloimmmunization

Answer 9

</= 0.1mL

entering maternal circulation

Question 10

Surveillance Interval if Antibody titer </= 1:8

in RhD

Answer 10

q4w

Question 11

How to use MCA doppler to predict fetal anemia?

PSV value?

Answer 11

Peak systolic Velocity >1.5x median for GA

Question 12

Delivery timing of Alloimmunized Pt’s fetus

Answer 12

mild hemolysis: IOL reasonable if ~>37-38wks
severe hemolysis: transfusion 30-32w GA -> delivery 32-34w GA after BMZ

Question 13

Most frequently encountered non-RhD Ab?

Answer 13

Lewis

Question 14

Preeclampsia High Risk Factors

Just one to start ASA at 12w

Answer 14

1. hx PEC
2. multifetal
3. cHTN
4. DM
5. Renal D/z
6. Autoimmune dz

Question 15

Preeclampsia Mod-Risk
Factors

just two to start ASA

Answer 15

1. Nulliparity
2. Obesity
3. family hx PEC
4. Low SES
5. Age >35
6. other personal hx

Question 16

Rh(D) screen result:
“Weak D”

Rhogam or nah?

Why?

Answer 16

pt has D antigen

Rhogam!
also,if transfusing: Rh neg blood!

might be missing a key part of antigen, develop Abs to it, and become senzitized

Question 17

What has higher risk of sensitiziation? amniocentesis vs CVS

Answer 17

CVS: 14%
amnio: 6%

delivery: ~50%

Question 18

Neonatal Alloimmune Thrombocytopenia (NAIT) MoA

Ag?

maternal platelet count

Answer 18

maternal alloimmunization to fetal platelets

most commonly: HPA-1t (mom negative, fetus positive)

usually normal

Question 19

NAIT fetal consequences

which pregnancy?

Answer 19

1. neonatal petechiae
2. fetal thromboctyopenia (<20,000)
3. intracranial hemorrhage

can occur in first pregnancy

Question 20

NAIT mgmt

timing in pregnancy

Answer 20

1. weekly fetal IVIG +/- prednisone
2. MFM / frequent ultrasound

start ~12-20wks GA