Final- ABO-Rh Isoimmunization

Question 1

what does isoimmunization mean?

Answer 1

sensitization of the mother to a fetal antigen that the mother does not carry

Question 2

how does isoimmunization occur?

Answer 2

• 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)

Question 3

the mother become sensitives how? when does this most often occur?

Answer 3

• fetal leaking blood through the placenta

- delivery (also trauma, amniocentesis, and chorionic villi sampling)

Question 4

what is the consequence of ABO incompatibility?

Answer 4

causes mild fetal disease (hemolytic anemia)

most antibodies are IgM which do not cross the placenta

Question 5

if mother if Rh negative, and father is Rh positive assume

Answer 5

baby is Rh positive

Question 6

Rh factor D rarely affects a woman’s first pregnancy. why?

Answer 6

the first pregnancy is generally the “sensitizing” experience. with initial exposure maternal IgM Ab are formed, subsequent antibodies are IgG which can cross placenta

Question 7

in subsequent pregnancy when IgG antibodies are formed, what happens?

Answer 7

IgG antibodies bind with the Rh antigen on the fetal red blood cells. causes erythroblastosis fetalis (hemolytic disease of newborn)

Question 8

Antenatal ssx of erythroblastosis fetalis/fetal hydrops

Answer 8

• Generalized edema, especially scalp edema and ascites
• Enlarged heart, pericardial effusion
• Hepatosplenomegaly
• Intra-uterine death, stillbirth

Question 9

treatment for antenatal erythroblastosis fetalis?

Answer 9

intra-uterine transfusions through the umbilical vein

Question 10

Postpartum ssx of erythroblastosis fetalis/fetal hydrops

Answer 10

• 15% have mild disease that is only apparent on laboratory tests
• Jaundice in first 24 hours of life
• Respiratory distress
• Heart failure, edema, hepatosplenomegaly

Question 11

treatment for postpartum erythroblastosis fetalis?

Answer 11

• Exchange transfusions with Type O, Rh negative blood cross-matched with the mother
• Phototherapy for hyperbilirubinemia/jaundice

Question 12

what percent of women who are Rh negative will become sensitized in 1st pregnancy?

Answer 12

16%

Question 13

RhoGAM given when will decrease risk the most dramatically?

Answer 13

at 28 weeks, reduces risk to .1%

used to be given only post delivery, reduces to 1-2%

Question 14

what dose of RhoGAM is usually adequate postpartum?

Answer 14

300 µg (covers up to 30 mL of fetal blood exposure)

Question 15

if you fear that the mother was exposed to more than 30 mL of blood during delivery, what test might you run?

Answer 15

Kleinhauer-Betke test (to determine amount of fetal blood in maternal circulation)

Question 16

Events necessitating RhoGAM administration?

Answer 16

SAB or therapeutic abortion 
Chorionic villi sampling or amniocentesis
Ectopic pregnancy
2nd or 3rd trimester procedures
Trauma such as falls, MVAs
Placental abruptions

Question 17

prenatal management includes

Answer 17

• 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

Question 18

postpartum management includes

Answer 18

• 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)

Question 19

during postpartum care, if neonate if Rh negative what do we do?

Answer 19

nothing, mother doesn’t need RhoGAM

Question 20

during postpartum care, if neonate if Rh positive what do we do?

Answer 20

give mom one 300 µg dose of RhoGAM to prevent maternal sensitization. RhoGAM MUST be given within 72 hours of delivery.

Question 21

if RhoGAM is deemed necessary postpartum, how soon do we need to give it?

Answer 21

72 hours after delivery