7.1 Anemia, Polycythemia, Sickle Cell, and Leukopenia
Key Takeaways
- Sort a falling hemoglobin by mechanism: physiologic anemia of prematurity versus blood loss, hemolysis, or underproduction, using the reticulocyte count and the clinical clock.
- AACN does not publish a transfusion hematocrit cutoff; restrictive NICU transfusion practice exists, and unit protocols vary by respiratory support and stability.
- Polycythemia is often discussed at a venous hematocrit near 65 percent; hyperviscosity, hypoglycemia, and jaundice drive care, and partial exchange with saline is a conceptual option for symptomatic infants.
- Sickle cell disease is rarely symptomatic in neonates because fetal hemoglobin predominates, but a positive newborn screen still requires confirmatory testing and family teaching.
- Neutropenia raises bacterial infection risk; alloimmune neutropenia can appear in an otherwise well infant with a very low ANC until maternal antibody wanes.
7.1 Anemia, Polycythemia, Sickle Cell, and Leukopenia
Quick Answer: Sort a falling hemoglobin by mechanism: physiologic anemia of prematurity (limited erythropoietin, growth dilution, short red-cell life, phlebotomy) versus blood loss, hemolysis, or underproduction. The reticulocyte count and the story separate them. AACN Certification Corporation does not publish a transfusion cutoff; restrictive NICU transfusion practice exists, and unit protocols vary. Polycythemia is often discussed at a venous hematocrit near 65%, with hyperviscosity as the real danger. Sickle cell disease is rarely symptomatic in neonates because fetal hemoglobin (HbF) predominates, but the newborn screen still matters. Neutropenia raises infection risk; alloimmune neutropenia can appear in an otherwise well infant.
Blood-cell disorders sit in the Hematology/Immunology slice of the 20% Endocrine, Hematology/Immunology, GI, Renal/GU, and Integumentary domain on the current Neonatal CCRN Test Plan (exams on or after November 12, 2025). OpenExamPrep provides independent CCRN Neonatal study material covering those patient problems as listed by AACN Certification Corporation. This chapter is not a unit transfusion protocol and does not invent an official AACN hematocrit number.
A term cord hemoglobin commonly lands near 14-20 g/dL (many references center around 16-17 g/dL). Preterm infants often start lower. After birth, hemoglobin falls. That fall is expected. It becomes a problem when oxygen delivery fails, when the drop is abrupt, or when the marrow cannot answer. Typical quiet heart rates you should be fluent with: about 120-160 beats/min in a term neonate, often 140-180 in a preterm infant. An anemic infant may be tachycardic, pale, feeding poorly, or in high-output failure. A polycythemic infant may be plethoric, jittery, hypoglycemic, or tachypneic. Neither color tells you the mechanism by itself.
Four mechanisms of a low hemoglobin
Ask four questions at the same time:
- Is this the expected physiologic fall of a growing preterm infant?
- Did the infant lose blood (obstetric, occult, or iatrogenic)?
- Are red cells being destroyed (immune or nonimmune hemolysis)?
- Is the marrow failing to produce cells?
Reticulocytes are the hinge. A high reticulocyte count says the marrow is answering: look for loss or hemolysis. A low reticulocyte count with anemia says production is not matching need: physiologic erythropoietin lag, parvovirus, congenital hypoplastic anemia, or marrow suppression. Always pair the number with the clock. A baby who was pink at 10 minutes and white at 40 minutes has blood loss or acute hemolysis until proven otherwise, even if the first hematocrit has not caught up yet.
| Mechanism | Typical timing | Reticulocytes | Bedside clues | Exam trap |
|---|---|---|---|---|
| Physiologic anemia of prematurity | Nadir often 4-8 weeks (term nadir nearer 8-12 weeks) | Inappropriately low for the hemoglobin | Growing preterm, stable, no bleed, no jaundice burst | Transfusing every low number without a protocol |
| Acute blood loss | Minutes to hours | Rise after a lag | Pallor, tachycardia, shock; obstetric hemorrhage, subgaleal swelling, twin-twin donor | Waiting for a confirmatory hematocrit while the infant is crashing |
| Hemolysis | Hours to days | High | Jaundice, falling hemoglobin, hepatosplenomegaly, positive DAT if immune | Treating only the bilirubin and missing the anemia |
| Underproduction | Variable; hydrops if fetal | Low | Parvovirus, congenital infection, rare marrow failure | Calling every low reticulocyte count physiologic on day 1 |
Physiologic anemia of prematurity
Fetal red cells live a shorter life than adult cells. Term neonatal red cells last about 60-90 days; preterm cells often last about 40-60 days. The infant is growing, so the same red-cell mass is diluted into a larger body. After cord clamping, arterial oxygen tension rises from fetal values (often discussed near 25-30 mm Hg in utero) toward newborn values. The liver, still a major erythropoietin source in the fetus, is a sluggish sensor compared with the kidney. Erythropoietin (EPO) falls. The marrow naps. Hemoglobin drifts down.
In a term infant the nadir is commonly around 8-12 weeks, with hemoglobin often in the 9-11 g/dL range, and the infant is usually well. In a preterm infant the nadir arrives earlier and lower, often around 4-8 weeks, and hemoglobin values in the 7-9 g/dL range are discussed in growing, otherwise stable infants. That pattern is physiologic anemia of prematurity, not an automatic transfusion order.
Phlebotomy makes the physiology worse. An extremely low-birth-weight infant can lose a clinically important fraction of blood volume in laboratory draws during the first week. Blood conservation is treatment: batched labs, microtainers, in-line blood gas sampling, questioning daily routine panels, and delayed cord clamping at birth when the obstetric and neonatal teams can do it safely. Recombinant EPO is used in some units as an adjunct; it is not a substitute for fewer needle sticks.
Blood-loss anemia
Acute loss presents with pallor, tachycardia, weak pulses, and shock. The first hematocrit can be misleadingly normal until the remaining blood is diluted by interstitial fluid or crystalloid. Obstetric sources include placenta previa, abruption, vasa previa, incision into an anterior placenta, fetomaternal hemorrhage, and twin-twin transfusion (the donor twin). Neonatal sources include subgaleal hemorrhage after vacuum or forceps (a progressive, potentially exsanguinating scalp collection), intracranial hemorrhage, pulmonary hemorrhage, and iatrogenic arterial sampling disasters. Kleihauer-Betke testing or flow cytometry looks for fetal cells in the maternal circulation when fetomaternal hemorrhage is suspected.
Chronic intrauterine loss (slow fetomaternal bleed, twin-twin donor) produces pallor with a better-expanded intravascular volume, reticulocytosis, and sometimes hydrops. The infant may tolerate a lower hemoglobin than an acute bleed of the same number because there was time to compensate. Still treat shock if it is present.
A worked contrast: a 3.2 kg term infant is born after a silent fetomaternal hemorrhage, heart rate 190, gray, capillary refill 4 seconds, hemoglobin 6 g/dL. That infant needs volume and red cells now, not a lecture on the six-week nadir. A former 26-week infant at 6 weeks of life, off support, gaining weight, hemoglobin 8.2 g/dL, reticulocytes inappropriately modest, bilirubin not spiking, stool occult-negative, is the physiologic story until a protocol or symptoms say otherwise.
Hemolysis and underproduction
Immune hemolysis is Hemolytic Disease of the Newborn (section 7.3). Preview it so you do not miss a positive Direct Antiglobulin Test (DAT), a rising bilirubin, and a falling hemoglobin in the same infant. Nonimmune hemolysis includes G6PD deficiency (X-linked; oxidant stress; more jaundice than chronic anemia in many neonates), hereditary spherocytosis, sepsis- or DIC-related fragmentation, and rare enzyme defects. Look for jaundice, hepatosplenomegaly, a high reticulocyte count, and a falling hemoglobin without a pool of lost blood.
Underproduction on day 1 is not physiologic anemia of prematurity. Parvovirus B19 infects erythroid precursors and can cause fetal hydrops and a low-reticulocyte anemia. Congenital viral infection, rare Diamond-Blackfan anemia, and marrow infiltration belong here. Iron deficiency is a later-preterm-nursery story if supplementation is missed; it is not the explanation for a pale 2-hour-old.
Transfusion principles without an invented AACN cutoff
Packed red blood cells (PRBCs), typically 10-15 mL/kg, raise oxygen-carrying capacity. Many nurseries use irradiated, leukoreduced, CMV-safe products for neonates. Infuse over a protocolized interval (often 2-4 hours unless the infant is exsanguinating). Watch volume overload in a failing heart. A rough teaching expectation is that 10-15 mL/kg of packed red cells raises hemoglobin on the order of 2-3 g/dL, but the clinical response still depends on ongoing loss or hemolysis.
Restrictive NICU transfusion practice exists. Large trials in extremely preterm infants (including programs commonly discussed as PINT, ETTNO, and TOP) compared higher versus lower hemoglobin thresholds and did not show a clear neurodevelopmental mandate for liberal transfusion. Many units therefore keep higher thresholds for infants on mechanical ventilation or significant oxygen and lower thresholds for stable, growing infants breathing room air. Exact grams-per-deciliter cutoffs live in your written protocol. AACN's Neonatal CCRN Test Plan names blood-cell disorders as a patient problem. It does not publish an official transfusion hematocrit. Do not invent one on the exam or at the bedside.
Transfuse for symptoms of inadequate oxygen delivery (persistent tachycardia, severe new apnea, lactic acidosis, heart failure) in context, not for a number in isolation. Feeding practices around transfusion (the TANEC conversation) vary by unit; follow local policy rather than improvising a national rule. Practice application items for this exam sit at /practice/ccrn-neonatal.
Polycythemia and hyperviscosity
Polycythemia is commonly discussed at a venous hematocrit of about 65% (hemoglobin often in the 22 g/dL neighborhood). Capillary hematocrits run higher than venous samples; confirm a high capillary value with a venous specimen before you treat a number. The physiology that injures is hyperviscosity: sluggish flow, impaired oxygen delivery despite a high hemoglobin, and risk to brain, gut, and kidney.
Causes include delayed cord clamping or cord milking (usually a modest rise), intrauterine growth restriction, infant of a diabetic mother, the recipient twin in twin-twin transfusion, maternal smoking, high altitude, Beckwith-Wiedemann, and some infants with trisomy 21. Extra red cells also consume glucose, so hypoglycemia rides along. Extra breakdown later feeds jaundice. Full IDM complications beyond the high hematocrit belong in Chapter 13; here the heme action is viscosity, glucose, and whether a partial exchange is even on the table.
Symptoms include plethora, lethargy or irritability, jitteriness, poor feeding, tachypnea, hypoglycemia, jaundice, thrombocytopenia, and, in severe cases, seizures, stroke, or necrotizing enterocolitis. Many infants with a hematocrit a little above 65% are asymptomatic.
Partial exchange transfusion is the conceptual treatment for symptomatic hyperviscosity: remove whole blood and replace with isotonic saline to lower hematocrit while keeping intravascular volume stable. The exchanged volume is conceptually blood volume times (observed hematocrit minus desired hematocrit) divided by observed hematocrit. Desired hematocrit is a protocol number, often discussed toward the mid-50s, not an AACN constant. Practice has shifted toward observation and hydration for asymptomatic infants rather than automatic exchange for every 65%. Follow the unit. Do not use FFP as the default replacement fluid for this purpose in modern teaching.
Sickle cell disease in the neonate
Hemoglobin S polymerizes when deoxygenated and distorts red cells. In the newborn, HbF is the dominant hemoglobin (often 60-90% at birth). HbF inhibits HbS polymerization. Vaso-occlusive pain, dactylitis, and acute chest syndrome are therefore rare in the first neonatal days and weeks. They become the pediatric story as HbF falls over the first 3-6 months.
What is testable now is the newborn screen. Patterns such as FS (sickle cell disease), FSC (HbSC), and FSA (S/beta-thalassemia) need confirmatory testing and hematology follow-up. Teach families that fever will later be an emergency, that penicillin prophylaxis is typically started in early infancy (often discussed by about 2 months of age once the diagnosis is confirmed), and that this NICU admission is not the time to diagnose a sickle crisis because the infant is jittery. Jaundice can still occur; hemolytic disease and G6PD remain on the jaundice list. Pediatric sickle-cell inpatient care lives on other exams; neonatal CCRN items usually test the HbF protection plus screen pairing. Adult CCRN pages at /study-guides/ccrn do not replace this neonatal pattern.
Leukopenia and neutropenia
Neutropenia is often discussed when the absolute neutrophil count (ANC) falls below about 1500/µL, with severe neutropenia often discussed below 500/µL. Definitions vary with postnatal age and gestational age; use the unit reference range. Early-onset sepsis consumes neutrophils. Preeclampsia and pregnancy-induced hypertension suppress marrow in many preterm infants; counts often recover over several days. Congenital viral infection and drugs are less common. Rare marrow-failure syndromes exist.
Neonatal alloimmune neutropenia occurs when the mother makes IgG against a paternal neutrophil antigen (HNA antigens) that the fetus inherited. The infant can look well and still have a dangerously low ANC. Infection risk is real until the antibody wanes and marrow recovers, often over weeks. Protective care, prompt evaluation of fever or new apnea, and specialist-directed G-CSF in selected severe or infected cases are the nursing frame. G-CSF is not automatic for every recovering preeclampsia-associated neutropenia.
Leukopenia is a broader low white count; the infection-risk conversation in neonates is usually about neutrophils. A falling ANC in a newly sick infant is sepsis until the workup says otherwise. A stable, well, first-week preterm infant with an ANC of 900 whose mother had severe preeclampsia is a different story from an ANC of 200 with petechiae, omphalitis, and shock.
Bedside sequence
- Color, heart rate, perfusion, and a confirmed hemoglobin or hematocrit.
- Classify: physiologic versus loss versus hemolysis versus underproduction.
- Check reticulocytes, bilirubin, DAT when hemolysis is plausible, and a maternal-fetal hemorrhage test when the infant is unexpectedly anemic at birth.
- Transfuse from symptoms plus the unit protocol, not from an invented AACN cutoff.
- Treat polycythemia as a viscosity and glucose problem; confirm venous hematocrit.
- Treat a positive sickle screen as a follow-up and teaching problem, not as neonatal vaso-occlusion.
- Treat severe neutropenia as an infection-risk problem, including alloimmune disease in a well-looking infant.
A former 27-week infant is now 6 weeks old, off oxygen, gaining weight, with hemoglobin 8.0 g/dL, a low reticulocyte count, no jaundice spike, and no bleeding. Which mechanism best explains this pattern?
A term infant with intrauterine growth restriction has a confirmed venous hematocrit of 68%, hypoglycemia, plethora, and lethargy. Which interpretation should guide the next team discussion?
Why is sickle cell disease rarely a cause of vaso-occlusive pain in the first neonatal days, and what action still matters?
A well-appearing term neonate has an ANC of 400/µL, no current infection, and a previous sibling who had isolated neutropenia. Which diagnosis should be on the problem list?