View source for Hemolytic disease of the newborn

==Background==
*Hemolytic disease of the fetus and newborn (HDFN), also known as erythroblastosis fetalis, is a condition in which maternal alloantibodies cross the placenta and destroy fetal/neonatal red blood cells, causing hemolytic anemia and unconjugated hyperbilirubinemia.<ref name="StatPearls">Hemolytic Disease of the Fetus and Newborn. ''StatPearls''. NCBI. 2025.</ref> The spectrum ranges from mild self-limited jaundice (most ABO cases) to fatal hydrops fetalis (severe Rh disease).
*The emergency physician encounters HDFN as early-onset neonatal jaundice (within the first 24 hours — always pathologic), severe anemia in a neonate, or a readmission for rapidly rising bilirubin.
*Timely recognition is critical because untreated severe hyperbilirubinemia causes kernicterus.
* ABO incompatibility is now the most common cause of HDFN in the Western world, following the success of anti-D (RhoGAM) prophylaxis in preventing Rh disease<ref name="PMC_HDN">Haemolytic disease of the newborn. ''Arch Dis Child Fetal Neonatal Ed''. 2007;92(2):F83-F88. PMC2675453.</ref>
* Rh (D) incompatibility remains the most severe form but is now uncommon with appropriate prevention
*Other minor blood group antigens (Kell, Duffy, Kidd, MNS) cause approximately 10% of severe cases; anti-Kell deserves special attention<ref name="AMBOSS">Hemolytic disease of the fetus and newborn. ''AMBOSS''. 2024.</ref>

{| class="wikitable"
|-
! Feature !! '''ABO incompatibility''' !! '''Rh (D) incompatibility''' !! '''Anti-Kell'''
|-
| Frequency || '''Most common''' cause of HDFN || Now uncommon (with prophylaxis) || ~10% of severe cases
|-
| First pregnancy affected? || '''Yes''' (preexisting natural anti-A/B IgG) || Usually '''no''' (sensitization during first pregnancy; affects subsequent) || Yes (if prior transfusion) or subsequent pregnancies
|-
| Typical severity || '''Mild to moderate''' || '''Moderate to severe''' || '''Severe'''
|-
| Direct Coombs (DAT) || Weakly positive or '''negative''' || '''Strongly positive''' || Positive
|-
| Anemia severity || Usually mild || Can be severe → hydrops || '''Severe''' (suppresses erythropoiesis directly; anemia out of proportion to hemolysis)
|-
| Hydrops fetalis || Rare || '''Can occur''' || Can occur
|-
| Bilirubin rise || Moderate || '''Rapid and severe''' || May be '''less than expected''' despite severe anemia (suppressed RBC production)
|-
| Prevention || None available || '''Anti-D immunoglobulin (RhoGAM)''' || Avoid Kell-positive transfusions in women of childbearing age
|}

===Mechanism===
*Mother lacks an antigen present on fetal RBCs (inherited from father)
*Maternal immune system produces IgG antibodies against the fetal antigen
*IgG crosses the placenta → binds fetal RBCs → extravascular hemolysis (in fetal spleen/liver)
*Hemolysis → anemia + increased unconjugated bilirubin production
*In utero: bilirubin is cleared by the placenta, so the fetus is ''not'' jaundiced; however, severe anemia → high-output cardiac failure → hydrops fetalis
*After birth: the neonatal liver cannot conjugate the sudden bilirubin load → unconjugated hyperbilirubinemia → risk of [[Kernicterus|kernicterus]]

==Clinical features==
===Early-onset jaundice (the cardinal sign)===
*'''Jaundice within the first 24 hours of life is ALWAYS pathologic''' and HDFN must be considered<ref name="StatPearls"/>
*This distinguishes HDFN from physiologic jaundice (which appears after 24-48 hours)
*Bilirubin may rise rapidly: rate of rise >0.5 mg/dL/hour suggests significant hemolysis and warrants urgent intervention

===Spectrum of severity===
* Mild: jaundice only; no significant anemia; responds to phototherapy (most ABO cases)
* Moderate: significant jaundice + anemia; may require IVIG and/or exchange transfusion
* Severe: profound anemia, hepatosplenomegaly (from extramedullary hematopoiesis), edema, ascites → hydrops fetalis
* Fatal: stillbirth or neonatal death from severe anemia, heart failure, or kernicterus

===Examination findings===
* Jaundice (scleral icterus, yellow skin)
* Pallor (anemia — may mask cyanosis)
* Hepatosplenomegaly (extramedullary hematopoiesis; Rh disease more than ABO)
* Edema, ascites, pleural effusions (hydrops — severe cases)
* Petechiae (thrombocytopenia from marrow replacement or DIC)
* Lethargy, poor feeding, hypotonia (early bilirubin encephalopathy — see [[Kernicterus]])

===Late anemia (readmission risk)===
*Neonates treated for HDFN may develop late anemia at 2-8 weeks of age as maternal antibodies continue to hemolyze neonatal RBCs
*May present to the ED with pallor, poor feeding, tachycardia, respiratory distress
* Check hemoglobin in any HDFN infant readmitted for any reason

==Differential diagnosis==
===Neonatal jaundice within 24 hours===
* HDFN (ABO, Rh, minor antigens) — this page
* [[G6PD deficiency]] — most common enzyme deficiency causing neonatal hemolysis worldwide; often triggered by oxidative stress; Coombs-negative
* [[Hereditary spherocytosis]] — family history; spherocytes on smear; Coombs-negative; osmotic fragility increased
* [[Sepsis]] — ill-appearing; fever or hypothermia; WBC abnormalities
* Enclosed hemorrhage (cephalohematoma, subgaleal hemorrhage) — resorbing blood → bilirubin production; no hemolysis markers
* [[Crigler-Najjar syndrome]] — unconjugated hyperbilirubinemia without hemolysis (normal reticulocyte count, Coombs-negative, normal haptoglobin)
* Pyruvate kinase deficiency — rare; chronic hemolytic anemia; Coombs-negative

===Key distinguishing features of HDFN===
* Positive direct antiglobulin test (DAT/Coombs) — confirms antibody on neonatal RBCs (though may be weakly positive or negative in ABO disease)
* Blood type mismatch between mother and infant
* Elevated reticulocyte count (appropriate marrow response to hemolysis)
* Spherocytes on peripheral smear (especially in ABO incompatibility)

==Evaluation==
===ED workup===
* Fractionated bilirubin (total and direct): expect predominantly unconjugated
* Maternal and infant blood type and Rh: identifies the incompatibility
* Direct antiglobulin test (DAT/direct Coombs test): positive confirms antibody coating neonatal RBCs
**Strongly positive in Rh disease; may be weakly positive or negative in ABO disease (does not exclude ABO HDFN)
* CBC with reticulocyte count: anemia + elevated reticulocytes (expect >5-10%; may be markedly elevated)
* Peripheral blood smear: spherocytes (especially ABO); nucleated RBCs (erythroblastosis); polychromasia
* Haptoglobin, LDH: hemolysis markers (haptoglobin low, LDH elevated)
* Albumin level: low albumin reduces bilirubin binding capacity and lowers the threshold for kernicterus
* Blood glucose: neonates with hemolytic disease may be hypoglycemic

===Additional testing===
* Maternal antibody screen (indirect Coombs test): identifies circulating maternal antibodies; identifies non-D alloantibodies (Kell, Duffy, etc.)
* Antibody identification panel: if indirect Coombs is positive, to identify specific antibody
* Cord blood bilirubin (if obtained at delivery): >3.5 mg/dL suggests significant hemolysis<ref name="Medscape_HDN">Hemolytic Disease of the Newborn Treatment & Management. ''Medscape''. 2024.</ref>

===Interpreting the bilirubin===
*Use '''hour-specific bilirubin nomograms''' (Bhutani nomogram) — plot the bilirubin level against the infant's age in hours to determine risk zone<ref name="StatPearls"/>
*Neurotoxicity risk factors that lower the treatment threshold: prematurity (<38 weeks), isoimmune hemolytic disease (positive DAT), G6PD deficiency, asphyxia, sepsis, acidosis, hypoalbuminemia (<3 g/dL)

==Management==
===Phototherapy===
*'''Initiate immediately''' for any neonate with HDFN and bilirubin at or approaching the phototherapy threshold for age<ref name="StatPearls"/>
* Intensive phototherapy: high-irradiance blue LED light (460-490 nm); maximize skin surface exposure
*Phototherapy converts unconjugated bilirubin into water-soluble photoisomers excreted without hepatic conjugation
*Continue until bilirubin is well below the exchange transfusion threshold and declining
*Phototherapy indications specific to HDFN (more aggressive than non-hemolytic jaundice):
**Cord bilirubin >3.5 mg/dL: start immediately
**Bilirubin rising >0.5 mg/dL/hour despite phototherapy: escalate to intensive phototherapy and prepare for exchange transfusion

===Intravenous immunoglobulin (IVIG)===
* IVIG 0.5-1 g/kg IV if bilirubin is rising rapidly (>0.5 mg/dL/hour) despite intensive phototherapy, or if bilirubin is approaching exchange transfusion threshold<ref name="Medscape_HDN"/>
*Mechanism: blocks Fc receptors on neonatal reticuloendothelial cells → reduces antibody-mediated RBC destruction
*May avoid the need for exchange transfusion (NNT ~3-6)
*Can repeat once if needed
* Caution: rare but reported association with necrotizing enterocolitis (NEC) in late preterm/term infants

===Exchange transfusion===
*'''Definitive emergency treatment''' for severe HDFN with dangerously elevated bilirubin or signs of acute bilirubin encephalopathy<ref name="StatPearls"/>
* Double-volume exchange (twice the infant's blood volume, ~160-170 mL/kg)
*Removes: circulating unconjugated bilirubin, antibody-coated RBCs, and free maternal antibodies
*Replaces with: fresh donor RBCs that lack the offending antigen
* Blood selection:
** Rh disease: O-negative, Rh-negative, crossmatched against maternal serum
** ABO disease: O-type RBCs with AB plasma (or type-specific), Rh-compatible
**All blood should be irradiated and leukodepleted
*Indications:
**Cord hemoglobin <10 g/dL with hydrops<ref name="PMC_HDN"/>
**Bilirubin rising >0.5 mg/dL/hour despite intensive phototherapy + IVIG
**Bilirubin at or above the exchange transfusion threshold for age on nomogram
**Any signs of acute bilirubin encephalopathy (lethargy, opisthotonus, seizures)
* Give IV albumin 1 g/kg before exchange transfusion (binds free bilirubin, increases efficiency of exchange)

===Simple transfusion===
*For '''significant anemia''' (hemoglobin <7-10 g/dL depending on clinical status) without dangerously elevated bilirubin
*Also for late anemia on readmission (ongoing hemolysis after initial hospitalization)
*Use irradiated, leukodepleted, antigen-negative packed RBCs

===Supportive care===
*IV dextrose-containing fluids (prevent hypoglycemia; maintain hydration)
*Frequent bilirubin monitoring (every 4-6 hours during active hemolysis)
*Monitor hemoglobin serially (hemolysis is ongoing)
*Iron supplementation (after acute phase; hemolysis depletes iron stores)
*Folic acid supplementation
* Avoid medications that displace bilirubin from albumin: sulfonamides, ceftriaxone, salicylates

==Disposition==
* All neonates with confirmed HDFN and significant hyperbilirubinemia: admit
**NICU if exchange transfusion anticipated, hydrops present, or signs of encephalopathy
**Well-baby unit with continuous phototherapy if mild-moderate disease
* Readmission for late anemia: admit if symptomatic anemia; transfuse as needed; discharge with close hematology/pediatric follow-up and planned hemoglobin checks at 1-2 week intervals
* Discharge criteria after acute HDFN:
**Bilirubin declining and below phototherapy threshold
**Hemoglobin stable and adequate
**Feeding well
** Arrange follow-up hemoglobin check within 48-72 hours (and again at 1-2 weeks) — late anemia is common and frequently missed
* Prevention counseling (Rh disease):
**Ensure Rh-negative mothers receive '''anti-D immunoglobulin (RhoGAM)''' at 28 weeks gestation and within 72 hours of delivery of an Rh-positive infant
**Also indicated after miscarriage, ectopic pregnancy, amniocentesis, abdominal trauma, or any event that may cause fetomaternal hemorrhage

==See Also==
*[[Neonatal jaundice]]
*[[Kernicterus]]
*[[Neonatal hepatitis]]
*[[Crigler-Najjar syndrome]]
*[[Gilbert syndrome]]
*[[G6PD deficiency]]
*[[Hereditary spherocytosis]]
*[[Hydrops fetalis]]

==External Links==
*[https://www.ncbi.nlm.nih.gov/books/NBK557423/ StatPearls — Hemolytic Disease of the Fetus and Newborn]
*[https://pmc.ncbi.nlm.nih.gov/articles/PMC2675453/ Arch Dis Child — Haemolytic disease of the newborn (2007)]
*[https://emedicine.medscape.com/article/974349-treatment Medscape — Hemolytic Disease of the Newborn Treatment & Management]
*[https://medlineplus.gov/ency/article/001298.htm MedlinePlus — Hemolytic disease of the newborn]

==References==
<references/>

[[Category:Pediatrics]]
[[Category:Heme/Onc]]