15 - Fetal Disorders

Question 1

Results from transplacental passage of maternal antibodies that destroy fetal red cells

Answer 1

Red cell alloimmunization

Question 2

What does alloimmunization lead to, defined as overproduction of immature fetal and neonatal red cells?

Answer 2

Erythroblastosis fetalis / hemolytic disease of the fetus and newborn

Question 3

Other possible causes of fetal anemia

Answer 3

Viral (parvovirus B19), alpha4-thalassemia, fetomaternal hemorrahge

Question 4

Methods through which fetal anemia may be identified

Answer 4

Fetal blood sampling, or Doppler evaluation of fetal middle cerebral peak systolic velocity

Question 5

Consequences of progressive fetal anemia

Answer 5

Heart failure, hydrops fetalis, death

Question 6

Prevalence of red cell alloimmunization in pregnancy

Answer 6

1%

Question 7

Test used to determine unbound antibodies in maternal serum

Answer 7

Indirect Coomb’s

Question 8

Clinically important group of antigens formerly termed Rh or rhesus groups

Answer 8

C, D, E groups

Question 9

Minimum amount of fetal erythrocytes that may lead to maternal sensitization within Rh / CDE alloimmunization

Answer 9

0.1 ml

Question 10

Prevalence of D alloimmunization complicating pregnancies

Answer 10

0.5 to 0.9%

Question 11

Likelihood that Rh / D-negative woman delivered of D-positive, ABO-compatible newborn will develop alloimmunization (without prophylaxis)

Answer 11

16%

Question 12

Distribution of sensitization of Rh / D-negative alloimmunization (at delivery, 6 months postpartum, subsequent pregnancy)

Answer 12

Delivery - 2%, 6-months postpartum - 7%, subsequent pregnancy - 7%

Question 13

Likelihood that Rh / D-negative woman delivered of D-positive, ABO-INCOMPATIBLE will develop alloimmunization (without prophylaxis)

Answer 13

2%

Question 14

Reason why Rh (+), ABO incompatible fetus produces less alloimmunization than an ABO compatible one

Answer 14

Erythryocyte destruction of ABO-incompatible cells, limiting sensitizing opportunities

Question 15

Fetomaternal hemorrhage, pregnancy loss related causes of red cell alloimmunization

Answer 15

Ectopic pregnancy, spontaneous abortion, elective abortion, fetal death

Question 16

Fetomaternal hemorrhage, procedure related causes of red cell alloimmunization

Answer 16

Chorionic villus sampling, amniocentesis, fetal blood sampling, evacuation of molar pregnancy

Question 17

Fetomaternal hemorrhage, other related causes of red cell alloimmunization

Answer 17

Delivery, abdominal trauma, abruptio, unexplained vaginal bleeding during pregnancy, manual placental removal, external cephalic version

Question 18

What is the grandmother effect of red cell alloimmunization

Answer 18

If maternal Rh + blood enters fetal circulation (Rh -), that fetus may subsequently develop antibodies during adulthood that will then cause alloimmunizatioin in an Rh + child (the grandchild of the original Rh + woman)

Question 19

Minor antigens / minor blood groups that may result in red cell alloimmunization

Answer 19

Kell antigens (most common), Duffy group, Kidd group

Question 20

T or F: While ABO incompatibility is the most common cause of hemolytic disease of the newborn, it does not cause appreciable hemolysis in the fetus

Answer 20

True

Question 21

Reason why ABO incompatibility is more of a pediatric (neonate) and not obstetric disease (fetus)

Answer 21

Because the IgM antibodies do not cross the placenta

Question 22

Percentage of fetuses from D-alloimmunized pregnancies that will have mild to moderate hemolytic anemia

Answer 22

25 to 30%

Question 23

Percentage of those with D-alloimmunization that will develop hydrops fetalis if no treatment is given

Answer 23

25%

Question 24

Frequency of titer monitoring if alloimmunization is detected but titer value is below the critical level

Answer 24

Every 4 weeks

Question 25

T or F: Serial titer assessment is indicated if a prior pregnancy was complicated by alloimmunization

Answer 25

False - the subsequent pregnancy is assumed to be at risk regardless of titer level

Question 26

Initial evaluation of alloimmunization begins with?

Answer 26

Determination of paternal erythrocyte antigen status

Question 27

T or F: If the father is negative for the red cell antigen to which the mother is sensitized, the pregnancy is not at risk

Answer 27

True

Question 28

The recommended test for detection of fetal anemia

Answer 28

Serial measurement of peak systolic velocity of fetal MCA