Final- ABO-Rh Isoimmunization Flashcards
what does isoimmunization mean?
sensitization of the mother to a fetal antigen that the mother does not carry
how does isoimmunization occur?
- the fetus inherits one or more major blood group factors from the father that the mother does not have
- 60% are caused by ABO incompatibility (most often by mother with type O blood, father with A or B)
the mother become sensitives how? when does this most often occur?
- fetal leaking blood through the placenta
- delivery (also trauma, amniocentesis, and chorionic villi sampling)
what is the consequence of ABO incompatibility?
causes mild fetal disease (hemolytic anemia)
most antibodies are IgM which do not cross the placenta
if mother if Rh negative, and father is Rh positive assume
baby is Rh positive
Rh factor D rarely affects a woman’s first pregnancy. why?
the first pregnancy is generally the “sensitizing” experience. with initial exposure maternal IgM Ab are formed, subsequent antibodies are IgG which can cross placenta
in subsequent pregnancy when IgG antibodies are formed, what happens?
IgG antibodies bind with the Rh antigen on the fetal red blood cells. causes erythroblastosis fetalis (hemolytic disease of newborn)
Antenatal ssx of erythroblastosis fetalis/fetal hydrops
- Generalized edema, especially scalp edema and ascites
- Enlarged heart, pericardial effusion
- Hepatosplenomegaly
- Intra-uterine death, stillbirth
treatment for antenatal erythroblastosis fetalis?
intra-uterine transfusions through the umbilical vein
Postpartum ssx of erythroblastosis fetalis/fetal hydrops
- 15% have mild disease that is only apparent on laboratory tests
- Jaundice in first 24 hours of life
- Respiratory distress
- Heart failure, edema, hepatosplenomegaly
treatment for postpartum erythroblastosis fetalis?
- Exchange transfusions with Type O, Rh negative blood cross-matched with the mother
- Phototherapy for hyperbilirubinemia/jaundice
what percent of women who are Rh negative will become sensitized in 1st pregnancy?
16%
RhoGAM given when will decrease risk the most dramatically?
at 28 weeks, reduces risk to .1%
used to be given only post delivery, reduces to 1-2%
what dose of RhoGAM is usually adequate postpartum?
300 µg (covers up to 30 mL of fetal blood exposure)
if you fear that the mother was exposed to more than 30 mL of blood during delivery, what test might you run?
Kleinhauer-Betke test (to determine amount of fetal blood in maternal circulation)
Events necessitating RhoGAM administration?
SAB or therapeutic abortion Chorionic villi sampling or amniocentesis Ectopic pregnancy 2nd or 3rd trimester procedures Trauma such as falls, MVAs Placental abruptions
prenatal management includes
- obtaining blood type and group and antibody screen by 12 weeks gestation
- at 28 weeks run antibody screen, if negative offer 28 week RhoGAM, if positive determine which factor the mom has become sensitized to and then determine if the father has that factor, if mom is sensitized to a factor the father has, refer to perinatologist
- repeat antibody screen at 36 weeks, if positive, manage as above
postpartum management includes
- immediately postpartum collect cord blood (generally can drain cord blood into red top tube from unbilical cord)
- labs on neonate (ABO-Rh, direct combs to tell you if sensitization has occurred, if positive, baby will be assessed for degree of anemia)
during postpartum care, if neonate if Rh negative what do we do?
nothing, mother doesn’t need RhoGAM
during postpartum care, if neonate if Rh positive what do we do?
give mom one 300 µg dose of RhoGAM to prevent maternal sensitization. RhoGAM MUST be given within 72 hours of delivery.
if RhoGAM is deemed necessary postpartum, how soon do we need to give it?
72 hours after delivery
