Isoimmunization

Question 1

what to do with any positive Ab screen?

Answer 1

paternal testing. if negative for antigen, then no risk for baby.

if positive, then follow-up maternal titers

Question 2

What critical titer?

Answer 2

1:16, although each lab is different

Question 3

in what % in first tri’s does mat-fetal hemorrhage happen? at term birth?
CVS?
amnio?
ECV?

Answer 3

3-11% in first tri
45% term birth
14% CVS
2-6% amnio
2-6% ECV

Question 4

what are the doses of rhogam?

Answer 4

rhogam - Rh Ig
mini-dose 50 micgrogm
regular dose 300 microgram - covers 15 cc of fetal blood cell transfusion (30 ml whole blood)
-> effective for 10-12 weeks (half life 24 days)

Question 5

how to manage weakly rh d positive?

Answer 5

treat like rh negative, could be:

• reduced # normal Rh D antigens
• partial antigens
• abnormal antigens

Question 6

what are minor antigens?

Answer 6

kell antigen (Kell Ab - IgG) -> kills
duffy antigen (Duffy Ab - IgG) - dies
lewis antigen (Lewis Ab- IgM) -> lives

Question 7

causes of non-immune hydrops:

Answer 7

• infection - parvovirus, cmv, syphillis
• alpha thalassemia (homozygous)
• structural: congenital heart defects (20%), supraventricular tachycardia, congenital cystic adenomatous formation
• chromosomal: 45X, T21
• placental: AV malformations (chorioangioma)

Question 8

work-up for non-immune fetal hydrops?

Answer 8

fetal ECHO
CBC, Ab screen, KB
parvo serologies, CMV acute phase serologies

(watch for mirror syndrome: pulmonary edema (90%), HTN (60%), proteinuria (40%))