RBC Antibodies

Antigens

markers on red blood cells, inherited from parents

most important antigen in pregnancy

D antigen (Rhesus factor)

RhD-positive

RhD antigen present

RhD-negative

RhD antigen absent

foreign antigen

triggers immune response

antibodies

Proteins that attach to antigens made from immune system, keeping them from harming the body

when antibodies form

body is exposed to foreign red blood cell antigens

exposure of foreign RBCs

pregnancy or blood transfusion

antibodies that can harm fetus

antibodies that cross the placenta

type of antibody that can cross placenta

Immunoglobin G, IgG

reason IgG can cross placenta

its size, structure, and Fc receptor allows it to cross

IgG antibodies effect (fetus)

destroy fetal RBCs, can cause HDFN (Hemolytic disease)

Anti-D

IgG antibody, developed in RhD-negative person exposed to RhD-positive blood, permanent

sensitisation

Rh-negative pregnant person's immune system becomes exposed to Rh-positive fetal blood cells, making anti-D antibodies in response

what produces anti-D in sensitisation

maternal immune system

Sensitisation can occur after

birth of RhD-positive baby, miscarriage/termination, vaginal bleeding, abdominal trauma, invasive procedures (e.g. ECV)

HDFN

hemolytic disease of the fetus and newborn

HDFN occurs

Maternal IgG antibodies cross placenta, antibodies bind to fetal red blood cells and destroy them, anaemia develops

mild consequence of HDFN

severe onset jaundice (<24 hours)

moderate consequence of HDFN

anaemia, hepatosplenomegaly (enlarged liver/spleen)

severe consequence of HDFN

hydrops fetalis (extra fluid in fetal compartments), heart failure, stillbirth, neonatal death

main purpose of RhD immunoglobulin (synthetic form of anti-D)

prevents maternal immune system response to RhD (preventing formation of permanent anti-D)

benefits of RhD immunoglobulin

doesn't harm fetus, doesn't sensitise mum, prevents HDFN

time RhD immunoglobulin is given

after sensitising events, within 72 hours

postnatal indication for RhD immunoglobulin

given if baby is RhD-positive

immune anti-D

mother's own antibodies

anti-D prophylaxis

injected, passive anti-D

Kleihauer test

Detects fetal cells in maternal blood.

Coombs test

detects antibodies against RBC's

Coombs Test, Direct (DAT)

used in newborns to test antibodies attached to RBC's (confirms HDFN, jaundice, or anaemia)

Coombs Test, Indirect (IAT)

used in pregnancy testing maternal blood for free antibodies in serum

times of routine blood test in relation to antibodies

booking, 28 and 36 weeks