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Necessary Laboratory Assessments for Neonates Exposed to Maternal Alloantibodies 

Newborn & Infant Laboratory Assessments

Please note that these are minimums. Some neonates will need labs more frequently, but all infants need a weekly hemoglobin/hematocrit check until 12 weeks old to check for delayed onset anemia.1 Anemia may be present without visible signs - blood tests are essential. When possible, use microtesting as anemia may be worsened by repeated testing. Do not give iron supplements without first testing the ferritin level. Infants with HDFN do not suffer from iron-deficiency anemia, but hemolytic anemia instead. Iron supplements can be deadly.2, 6


These tests are from Cord Blood. If the cord blood clots, it needs redrawn as soon as possible. 

  • DAT or Direct Coombs Test 

    • IAT or Indirect Coombs Test: This is needed as well if the DAT comes back negative and mom has: anti-C, anti-c, anti-Fya, anti-Good, anti-H, anti-Jra, anti-M, or anti-Mta antibodies. 

  • Antigen phenotype (optional) - This test may be done to confirm the results of a DAT/IAT or in place of the IAT with one of the Coombs Test Exceptions. 

  • Bilirubin 

    • Note: Alloimmunization (Isoimmune hemolytic disease) is a risk factor. All infants born to alloimmunized mothers are automatically medium or high risk depending on gestation. Infants born to mothers with antibodies will not be low risk. 

  • CBC (Complete Blood Count): including Hemoglobin/Hematocrit, Neutrophils, Platelets/Thrombocytes, and a Retic/Reticulocyte count.

0-1 Week Old (Days 1-7)

  • Bilirubin - checked every 4, 6 or 12 hours in the hospital. 

  • Bilirubin - checked daily when out of the hospital. This is especially important during days 4-6 when bilirubin due to alloimmunization tends to peak. 

  • Hemoglobin - checked usually at least 1 other time this week besides birth.

  • Retic

1-2 Weeks Old

  • Hemoglobin/Hematocrit - checked weekly (some docs do 2x a week if <4 weeks old).

  • Retic

  • Bilirubin - checked every other day if still an issue.

  • Neutrophil count and Thrombocyte/Platelet. 

3 Weeks Old 

  • Hemoglobin/Hematocrit - checked weekly

  • Retic

  • Bilirubin 1-2x a week to be sure it is still going down.

  • Neutrophil count and Thrombocyte/Platelet count may be repeated depending on the values from earlier.

4 Weeks Old - 12 Weeks Old

  • Hemoglobin/Hematocrit - checked weekly. This is especially important for weeks 4-6 when newborns have a normal drop in hemoglobin. Infants suffering from HDN can have a larger drop than normal and need their first transfusions during this window. This is not limited to infants whose mothers have had IUTs, but applies to all infants affected by isoimmunization. All infants need the weekly check until 12 weeks old or the hemoglobin is going up 2-3 weeks in a row. 

  • Retic - checked weekly (timing optional, but it is not necessary to check more often than weekly) to see if the infant is making new blood.

  • Other Tests - the Thrombocyte/Platelet count, and the Neutrophil count may be repeated every 2-4 weeks if needed. Thrombocytopenia and Neutropenia are both common side effects of isoimmunization/Hemolytic Disease of the Newborn. Neutropenia may last for up to 1 year in some cases.