Late one evening, a full blood count was received on a full term neonate who had just been delivered by caesarean section. The clinical notes read ‘pallor’. The results from the analyser were as follows:
Hb 64 g/L, MCV 118.9 fL, reticulocyte count 13.4 % (254 x 109/L), WBC 16.2 x 109/L and platelets 278 x 109/L.
A Hb result of 64 g/L is abnormally low for a newborn neonate; the normal range being 121 – 191 g/L in the above laboratory. A repeat specimen was requested. The Hb was now 60 g/L, confirming the initial result. Whilst the blood film was being stained a direct antiglobulin test (DAT) was performed with a negative result. Both the infant and mother were group O positive and an antibody screen performed on the mother was negative. The total bilirubin was 140 umol/L, NR (0-150 umol/L).
The infant was transfused with two units of packed cells.
The blood film revealed a nucleated red cell count (NRBC) of 674 NRBCs / 100 WBCs. The normal range being 1-25 NRBCs / 100 WBCs. The blood film image (x 400) demonstrates the markedly increased number of red cell precursors while the blood film images (x 1000) demonstrate marked dyserythropoiesis. Note the nuclear budding and cytoplasmic bridging, classical features of dysplasia.
A differential diagnosis on this infant would include a fetomaternal bleed or less probably Congenital Dyserythropoietic Anaemia (CDA). A Kleihauer test was performed on the mother to check for a fetomaternal bleed. The Kleihauer test was positive; the presence of 3.84 % fetal cells translated to a transplacental haemorrhage of 95.84 mls. Hence the initial diagnosis of a fetomaternal bleed was confirmed.
Some degree of fetomaternal transfusion occurs in approximately 50% of all pregnancies. The most frequently observed causes of occult haemorrhage prior to birth include abdominal or multiple trauma, amniocentesis in the third trimester, post external cephalic version, placental tumours and spontaneous haemorrhages. Haemoglobin values as low as 30 to 60 g/L have been recorded in infants who were born alive and survived.
The clinical manifestations of a fetomaternal haemorrhage depend on the rapidity with which it has occurred. If the haemorrhage has been prolonged, giving the fetus the opportunity to compensate for the anaemia, the infant may manifest only pallor at birth. However, if the haemorrhage is acute, the infant may be pale and sluggish, have gasping respirations and manifest signs of circulatory shock.
The blood film may also be informative. In an acute haemorrhage, the red cells are normochromic normocytic whereas in a more prolonged fetomaternal haemorrhage the red cells may be microcytic and hypochromic. Note that the NRBCs in this case exhibited ragged cytoplasm, a feature seen in iron deficiency. The MCV on this neonate was slightly raised at 118.9 fL, NR (101-117 fL). This was secondary to the significantly raised reticulocyte count of 13.4 % NR (4-7 %). In anaemia secondary to a fetomaternal haemorrhage the DAT test is negative and the infants are not jaundiced. The presence of a very high NRBC count is an index of fetal stress.
The diagnosis of a fetomaternal haemorrhage can be made with certainty by demonstrating the presence of fetal cells in the maternal circulation. This is done by performing the Kleihauer-Betke test. The Kleihauer image above demonstrates the presence of acid-resistant fetal red cells on a background of acid sensitive adult red cells that appear as ghost cells. Note that the Kleihauer-Betke method has been replaced by a flow cytometry test for the estimation of HbF in many laboratories.
The infant in this update maintained a stable haemoglobin post transfusion hence a potential diagnosis of CDA was not pursued. Mother and infant went home several days after confinement.