Anemia from blood loss at birth is manifested by two patterns of presentation, depending on the rapidity of blood loss.Acute blood loss after fetal-maternal hemorrhage, rupture ofthe umbilical cord, placenta previa, or internal hemorrhage (hepatic or splenic hematoma; retroperitoneal) is characterized by pallor, diminished peripheral pulses, and shock. Thereare no signs of extramedullary hematopoiesis and no hepatosplenomegaly. The hemoglobin content and serum iron levelsinitially are normal, but the hemoglobin levels decline duringthe subsequent 24 hours. Newborns with chronic blood loss caused by chronic fetal-maternal hemorrhage or a twin-totwin transfusion present with marked pallor, heart failure,hepatosplenomegaly with or without hydrops, a low hemoglobin level at birth, a hypochromic microcytic blood smear, anddecreased serum iron stores. Fetal-maternal bleeding occurs in50% to 75% of all pregnancies, with fetal blood losses rangingfrom 1 to 50 mL; most blood losses are 1 mL or less, 1 in 400 are approximately 30 mL, and 1 in 2000 are approximately 100 mL.
The diagnosis of fetal-maternal hemorrhage is confirmed by the Kleihauer-Betke acid elution test. Pink fetal RBCs are observed and counted in the mother’s peripheral blood smear because fetal hemoglobin is resistant to acid elution; adult hemoglobin is eluted, leaving discolored maternal cells (patients with sickle cell anemia or hereditary persistence of fetal hemoglobin may have a false-positive result, and ABO incompatibility may produce a false-negative result).
Hemolysis in utero resulting from any cause may produce a spectrum of clinical manifestations at birth. Severe hydropswith anasarca, heart failure, and pulmonary edema may prevent adequate ventilation at birth, resulting in asphyxia. Infantsaffected with hemolysis in utero have hepatosplenomegaly andpallor and become jaundiced within the first 24 hours afterbirth. Less severely affected infants manifest pallor and hepatosplenomegaly at birth and become jaundiced subsequently.Patients with ABO incompatibility often are asymptomaticand show no physical signs at birth; mild anemia with jaundicedevelops during the first 24 to 72 hours of life.
Because hydrops, anemia, or jaundice are secondary to many diverse causes of hemolysis, a laboratory evaluation is needed in all patients with suspected hemolysis. A complete blood count, blood smear, reticulocyte count, blood type, and direct Coombs test (to determine the presence of antibody-coated RBCs) should be performed in the initial evaluation of all infants with hemolysis. Reduced hemoglobin levels, reticulocytosis, and a blood smear characterized by polychromasia and anisocytosis are expected with isoimmune hemolysis. Spherocytes commonly are observed in ABO incompatibility. The determination of the blood type and the Coombs test identify the responsible antigen and antibody in immunologically mediated hemolysis.