Lesson of the Week: Importance of accurate assessment of fetomaternal haemorrhage after late abortionsBMJ 1996; 313 doi: https://doi.org/10.1136/bmj.313.7066.1200a (Published 09 November 1996) Cite this as: BMJ 1996;313:1200
- Imelda Bromilow, clinical scientista,
- J K M Duguid, consultant haematologista,
- S Walkinshaw, consultant haematologistb
- a National Blood Service, Mersey and North Wales Centre, Liverpool L7 8TW
- b Liverpool Women's Hospital, Liverpool L8 7SS
- Correspondence to: Dr Duguid.
- Accepted 10 September 1996
Anti-D immunoglobulin is routinely administered to RhD negative women after an abortion. Before 20 weeks of gestation 25 IU of anti-D immunoglobulin should be given and after 20 weeks of gestation 500 IU. The Kleihauer stain test should be routinely performed to assess the adequacy of this dose.1 RhD typing of the aborted fetus is not usually performed.
Fetal blood after late abortion in RhD negative women should be RhD typed to ensure appropriate anti-D immunoglobulin dosage
We report a case in which large doses of anti-D immunoglobulin were given inappropriately because the Kleihauer test detects only fetal haemoglobin; further testing with flow cytometry showed that the abortus was RhD negative.
A pregnant woman underwent a late termination of pregnancy for a lethal fetal malformation after 20 weeks of gestation. The procedure was carried out using mifepristone pessaries. There were no clinical problems: maternal blood loss was not excessive and the placenta was delivered normally. Anti-D immunoglobulin (500 IU) was given, and Kleihauer testing indicated that a fetal bleeding of about 100 ml had occurred. Additional anti-D immunoglobulin was given to a total dose of 10 500 U. Further Kleihauer testing 24 hours later showed that fetal cells were still evident in the maternal circulation.
Flow cytometry was then performed to assess more accurately the size of the fetomaternal haemorrhage. Flow cytometry used in this way detects RhD positive cells in a RhD negative circulation and gives a more objective assessment than the Kleihauer test for calculating the number of fetal cells after fetomaternal haemorrhage.2 Results for the original sample showed that there were no RhD positive cells in the maternal circulation, strongly suggesting that the fetus was RhD negative (fig 1).
This case highlights several points. Babies born to RhD negative mothers are RhD typed. If the baby is RhD negative then anti-D immunoglobulin is not required. RhD typing of a fetus (abortus) after a late (>20 weeks) termination of pregnancy is not, however, routine. After 20 weeks the fetus has a well established circulation, and large fetomaternal bleeds well in excess of 4 ml can occur. Monitoring of the size of fetomaternal haemorrhage should therefore be routinely undertaken using a Kleihauer test to ensure that an adequate dose of anti-D immunoglobulin has been administered. If this indicates that a large (>4 ml) fetomaternal haemorrhage has occurred the maternal sample should be tested by flow cytometry. This technique measures the number of RhD positive cells among RhD negative cells and is therefore an alternative way of RhD typing fetal blood after a fetomaternal haemorrhage.
Anti-D immunoglobulin specifically eliminates RhD positive fetal cells; it has no effect on RhD negative fetal cells. A Kleihauer result may remain strongly positive despite administration of large amounts of anti-D immunoglobulin because it detects fetal haemoglobin. This is what happened in our case. It shows the importance of RhD typing the fetus of a late termination of pregnancy, and if this cannot be done, the importance of the use of flow cytometry in conjunction with Kleihauer testing in cases with evidence of a clinically important volume of fetomaternal haemorrhage.
If this regimen were to be routinely adopted the unnecessary use of human anti-D immunoglobulin would be reduced, resulting in a more effective use of all resources and an improvement in the quality of patient care.
Conflict of interest None.
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