Increased numbers of nucleated red blood cells (NRBCs) may be present in a newborn infant if one or more causes are present.


Causes of increased numbers of NRBCs:

(1) fetal asphyxia with hypoxia

(1a) uteroplacental insufficiency

(2) intra-uterine fetal blood loss

(2a) fetal to maternal transfusion

(2b) donor in the twin to twin transfusion syndrome

(2c) lacerated blood vessel

(3) maternal diabetes

(4) intra-uterine placental blood loss

(4a) abruptio placenta

(4b) laceration of velamentous blood vessel

(5) intra-uterine hemolytic anemia

(5a) anti-D, anti-C or other anti-Rh antibodies

(6) trisomy 13 or 21

(7) severe hemoglobinopathy


ABO-incompatibility is unlikely to cause a significant increase in NRBCs by itself.


For a transient insult there is a lag time between the onset of the event and the appearance of the NRBCs (as little as 2 hours up to 48 hours). Once the problem is reversed then the NRBCs can disappear within a few hours. With severe intra-uterine asphyxia they can persist for up to a week or more after delivery (suggesting on-going problems with oxygenation).


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