Diseases

Question 1

What may result when ABO incompatibility occurs between mother and the newborn infant?

Answer 1

Isoimmune hemolytic anemia

Question 2

What blood types of baby and mother does isoimmune hemolytic anemia most commonly occur?

Answer 2

Blood type A or B infants born to type O mothers

Question 3

Describe the symptommatic clinical disease in isoimmune hemolytic anemia

Answer 3

compensated mild hemolytic anemia with reticulocytosis, microspherocytosis, and early-onset unconjugated hyperbilirubinemia

Question 4

Why is hemolytic process seen more in type O mothers as opposed to type A or B?

Answer 4

In type O mothers,isoantibody is predominantly 7S-IgG (immunoglobulin G) and is capable of crossing the placental membranes. Because of its larger size, the mostly 19S-IgM
(immunoglobulin M) isoantibody found in type A or type B mothers cannot cross

Question 5

Describe the incidence of ABO incompatability?

Answer 5

Risk factors for ABO incompatibility are present in 12% to 15% of pregnan-
cies, but evidence of fetal sensitization (positive direct Coombs test) occurs in only
3% to 4%. Symptomatic ABO hemolytic disease occurs in <1% of all newborn infants but accounts for approximately two-thirds of observed cases of hemolytic disease in the newborn

Question 6

Describe the pathophysiology of ABO incompatability

Answer 6

Transplacental transport of maternal isoantibody results in an immune reaction with the A or B antigen on fetal erythrocytes, producing characteristic micropherocytes.

Extravascular hemolysis of the end-stage spherocyte

ongoing hemolysis is balanced by compensatory reticulocytosis and shortening of the cell cycle time –> maintenance of erythrocyte indices within physiologic limits

paucity of A or B antigenic sites on the fetal (in contrast to the adult) erythrocytes and competitive binding of isoantibody to a myriad of other antigenic sites in other tissues may explain the often mild hemolytic process that occurs and the usual absence of progressive disease with subsequent pregnancies

Question 7

Risk factors for ABO incompatability?

Answer 7

A1 antigen in infant - has highest antigenicity and is assoc w/ greater risk of symptomatic dx. however hemolytic activity of anti-B Ab is higher than that of anti-A Ab and may produce a more severe disease, in particular among infants of african american descent

Elevated isohemagglutinins: antepartum intestinal parasitism or third-trimester immunisation with tenatus toxoid or pneumococcal vaccine may stimulate isoantibody titer to A or B antigens

Maternal immune serum globulin anti-A/B titers: Anti-A/B titers >512% are sig assoc w/ risk of ABO hemolytic disease of the newborn and may be an early indicator for therapy

Birth order: not a RF. Maternal isoantibody exists naturally and is independent of prior exposure to incompatible fetal blood group antigens

Question 8

Clinical presentation of ABO incompatability?

Answer 8

Jaundice: icterus often sole manifestation w/ clinically sig level of hemoysis. Onset usually <24hrs of life. Jaundice evolves at faster rate over early neonatal period than nonhemolytic physiologic pattern jaundice

Anemia: Because of the effectiveness of compensation by reticulocytosis in
response to the ongoing mild hemolytic process, erythrocyte indices are main-
tained within a physiologic range that is normal for asymptomatic infants of the
same gestational age. Additional signs of clinical disease (eg, hepatosplenomegaly
or hydrops fetalis) are extremely unusual but may be seen with a more progressive hemolytic process. Exaggerated physiologic anemia may occur at 8 to 12 weeks of age, particularly when treatment during the neonatal period required phototherapy or exchange transfusion.

Question 9

How to diagnose ABO incompatability?

Answer 9

Obligatory screening for infants with unconjugated hyperbilirubinemia
includes the following studies:

1. Blood type and Rh factor in mother and infant
2. Reticulocyte count
3. DCT
4. Blood smear
5. Bilirubin levels
6. Additional studies may be needed if nature of hemolytic process remains unclear

Question 10

Importance of Blood type and Rh factor resting in mother and infant in jaundiced babies?

Answer 10

establish risk factors for ABO incompatibility. Noninvasive prenatal typing can now be done using cell-free fetal DNA genotyping

Question 11

Importance of reticulocyte count when investigating ABO incompatability? What reticulocyte counts are pathological?

Answer 11

Elevated values after adjustment for gestational age and degree of anemia, if any, support the diagnosis of hemolytic anemia. For term infants,
normal values are 4% to 5%; for preterm infants of 30 to 36 weeks’ gestational age, values are 6% to 10%. In ABO hemolytic disease of the newborn, values range
from 10% to 30%.

Question 12

Importance of DCT when evaluating ABO incompatability?

Answer 12

Because there is very little antibody on the red blood cell (RBC), the direct Coombs test is often only weakly positive at birth and may become negative by 2 to 3 days of age. A strongly positive test is distinctly unusual and would direct attention to other isoimmune or autoimmune
hemolytic processes

Question 13

Importance of blood smear in evaluating ABO incompatability?

Answer 13

The blood smear typically demonstrates microspherocytes, polychromasia proportionate to the reticulocyte response, and normoblastosis above the normal values for gestational age. An increased number of nucleated RBCs in the cord blood could be a sign of ABO incompatibility.

Question 14

Importance of bilirubin levels (fractionated or total and direct) in evaluating ABO incompatability?

Answer 14

Indirect hyperbilirubinemia is mainly present and provides an index of the severity of disease. The rate at which unconjugated bilirubin levels are increasing suggests the required frequency of testing, usually every 4 to 8 hours until values plateau.

Question 15

What additional laboratory studies may be helpful in evaluating ABO incompatability?

Answer 15

1. Antibody identification (indirect Coombs test).The indirect Coombs test is
   more sensitive than the direct Coombs test in detecting the presence of maternal isoantibody and identifies antibody specificity. The test is performed on an eluate
   of neonatal erythrocytes, which is then tested against a panel of type-specific
   adult cells.
2. Maternal IgG titer.The absence in the mother of elevated IgG titers against
   the infant’s blood group tends to exclude a diagnosis of ABO incompatibility.

Question 16

General measures for post-partum management of ABO incompatability?

Answer 16

The maintenance of adequate hydration and evaluation for potentially aggravating factors (eg, sepsis, drug exposure, or metabolic disturbance) should be considered.

Question 17

Describe antepartum management of ABO incompatability

Answer 17

Because of the low incidence of moderate to severe ABO hemolytic disease, invasive maneuvers before term is reached (eg, amniocentesis
or early delivery) are usually not indicated.

Question 18

Describe role of phototherapy in managing ABO incompatability

Answer 18

Once a diagnosis of ABO incompatibility is established, phototherapy may be initiated before exchange transfusion is given. Because of the
usual mild to moderate hemolysis, phototherapy may entirely obviate the need for exchange transfusion or may reduce the number of transfusions required

Question 19

Describe role of Tin prophyrin in managing ABO incompatability

Answer 19

This can decrease the production of bilirubin and reduce the need for exchange transfusion and duration of phototherapy. It is an inhibitor of heme oxygenase, which is the enzyme that allows the production of bilirubin
from heme. The dose of stannsoporfin is 6 µmol/kg intramuscularly as a single
dose given within 24 hours of birth with severe hemolytic disease, and it is
available via compassionate use protocol.

Question 20

Describe the role of IV immunoglobulin in managing ABO incompatability

Answer 20

By blocking neonatal reticuloendothelial Fc
receptors and thus decreasing hemolysis of the antibody-coated RBCs, high-
dose intravenous immunoglobulin (IVIG; 1 g/kg over 4 hours) reduces serum
bilirubin levels and the need for blood exchange transfusion with ABO or Rh
hemolytic diseases. AAP recommends IVIG 0.5 to 1 g/kg over 2 hours if the TSB
is rising despite intensive phototherapy or if the TSB level is within 2 to 3 mg/dL
of the exchange level, can be repeated in 12 hours. Cochrane review (2018) does not recommend routine use of IVIG in alloimmune HDN because of low quality of evidence. Caution should be used when considering treatment with IVIG as there are emerging reports of increased incidence of necrotizing enterocolitis in
term and late preterm infants with hemolytic disease of the newborn and isoimmune neonatal thrombocytopenia who were treated with IVIG.

Question 21

Prognosis of ABO incompatability

Answer 21

For infants with ABO incompatibility, the overall prognosis is excellent.
Timely recognition and appropriate management of the rare infant with aggressive ABO hemolytic disease may avoid any potential morbidity or severe hemolytic anemia and secondary hyperbilirubinemia and the inherent risks associated with exchange transfusion with the use of blood products

Question 22

RF for birth injury?

Answer 22

Factors predisposing the infant to birth injury include macrosomia, prematurity, cephalopelvic disproportion, dystocia, prolonged labor, abnormal presentation, and certain operative deliveries, particularly vacuum extraction

Question 23

Describe erythema and abrasions in the context of birth injury?

Answer 23

Erythema and abrasions frequently occur when dystocia has occurred during labor as a result of cephalopelvic disproportion or when forceps have been used during delivery. Injuries caused by dystocia occur over the presenting part; forceps injury occurs at the site of application of the instrument. Forceps injury frequently has a linear configuration
across both sides of the face, outlining the position of the forceps. The affected areas should be kept clean to minimize the risk for secondary infection. These lesions usually resolve spontaneously within several days with no specific
therapy.

Question 24

Describe petechiae in the context of birth injury?

Answer 24

Occasionally petechiae are present on the head, neck, upper portion of the chest, and lower portion of the back at birth after a difficult delivery; they are observed more frequently after breech and precipitous deliveries and tight nuchal cord.

Question 25

Describe the etiology of petechiae in the context of birth injury?

Answer 25

Petechiae are probably caused by a sudden increase in intrathoracic and venous pressures during passage of the chest through the birth canal. An infant born with the cord tightly wound around the neck may have petechiae only above the neck

Question 26

DDx of petechiae in the context of birth injury?

Answer 26

Petechiae may be a manifestation of an underlying hemorrhagic disorder. The birth history, early appearance of the petechiae, and absence of bleeding from other sites help to differentiate petechiae caused by increased tissue pressure or trauma from petechiae caused by hemorrhagic disorders
. The localized distribution of the petechiae, absence of subsequent crops of new lesions, and a normal platelet count exclude neonatal thrombocytopenia. The platelet count also may be low because of infection or disseminated intravascular coagulation. Infections may be clinically distinguished from traumatic petechiae by the presence of other signs and symptoms. Disseminated intravascular coagulation usually is associated with excessive and
persistent bleeding from a variety of sites. Petechiae usually are distributed over the entire body when associated with systemic disease

Question 27

Treatment and prognosis of petechiae with regards to birth trauma?

Answer 27

If the petechiae are caused by trauma, neither corticosteroids nor heparin should be used. No specific treatment is necessary.

Traumatic petechiae usually fade within 2 or 3 days

Question 28

Describe ecchymosis in the context of birth trauma?

Answer 28

Ecchymoses may occur after traumatic or breech deliveries. The incidence is increased in premature infants, especially after a rapid labor and poorly controlled delivery. When extensive, ecchymoses may reflect blood loss severe enough to cause anemia and, rarely, shock. The reabsorption of blood from an ecchymotic area may result in significant hyperbilirubinemia

Question 29

Describe treatment and prognosis of ecchymosis in the context of birth injuries?

Answer 29

No local or systemic therapy is necessary. The rise in serum bilirubin that follows severe bruising may be decreased by the use of phototherapy. Ecchymoses
rarely result in significant anemia.

The ecchymoses usually resolve spontaneously within 1 week.