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This test counts the number of red blood cells in a sample of umbilical cord blood collected at birth. Red blood cells carry oxygen throughout the body using hemoglobin, and their concentration reflects the baby’s circulating red cell mass at the time of delivery.
Cord blood testing is often performed shortly after delivery to provide an early snapshot of a newborn’s blood status. The red blood cell count is commonly reviewed alongside related measures such as hemoglobin, hematocrit, and sometimes a blood smear or reticulocyte count to better understand the baby’s oxygen-carrying capacity and bone marrow activity.
Knowing the red blood cell count in cord blood helps identify conditions such as anemia or polycythemia, which can affect oxygen delivery and blood flow in a newborn. Clinicians may order this test when there are risk factors like maternal diabetes or hypertension, growth restriction, concerns for blood group incompatibility, twin-to-twin transfusion, or if the baby shows signs such as pallor, poor feeding, or breathing difficulty.
Results can guide next steps, which may include monitoring, additional blood tests, or treatments aimed at supporting the baby’s circulation and oxygen needs. Understanding the count early helps clinicians anticipate issues like jaundice or low blood sugar that can accompany abnormal red blood cell levels.
If the red blood cell count is lower than expected, it can suggest anemia. Causes may include blood loss around the time of birth, breakdown of red cells due to blood group incompatibility, or reduced production. Your care team may confirm with related tests, discuss possible causes, and decide on monitoring or treatment based on your baby’s condition.
If the count is higher than expected, it can suggest polycythemia, which may thicken the blood and reduce flow to organs. This can be associated with certain maternal conditions, timing of cord clamping, or the baby’s growth pattern. Clinicians often watch for symptoms and may order follow-up tests such as hemoglobin, hematocrit, reticulocyte count, bilirubin, blood type, and a direct antiglobulin test. Most babies do well, and your team will explain the findings and outline the plan that fits your newborn’s needs.
Reference intervals vary by laboratory, analyzer, methodology, population, and units. The ranges shown here are for education only. Always interpret your results against the reference interval printed on your own lab report.
Delayed cord clamping or cord milking can increase the baby’s red cell mass, which may raise the measured red blood cell count in cord blood compared with immediate clamping.
Preterm, term, and post-term infants can have different baseline red blood cell levels. Twin-to-twin transfusion, growth restriction, or acute blood loss around delivery can shift the count.
Diabetes, hypertension, smoking, high-altitude residence, and placental insufficiency can influence fetal red blood cell production and concentration at birth.
Rh or ABO incompatibility can increase red cell breakdown in the newborn, lowering the count and prompting follow-up tests such as a direct antiglobulin test.
Clotting, dilution, or contamination of the cord blood sample can affect accuracy. Proper collection from the cord vessel and prompt processing help ensure reliable results.
Intrauterine transfusions, significant maternal IV fluid shifts, or resuscitation factors can influence the measured red blood cell count in the immediate newborn period.
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