What do colleagues do in their practice regarding testing for feto-maternal bleeds and/or the use of micro versus full doses of RHIG

A colleague in Colorado has a question regarding what is a sufficient work-up for ruling out feto-maternal hemorrhage for patients who are candidates for RHIG, but who are in their first or second trimester of pregnancy? At the inquiring colleague's hospital, they do not do any work-up for feto-maternal hemorrhage for patients who qualify for a so called "micro dose" (50 micrograms) of RHIG during the first trimester of pregnancy. (Editor's note: According to a RHIG package insert, a single dose of approximately 50 micrograms of RHIG will suppress the immune response to 2.5 mL of Rh-positive red blood cells. Such a dose is therefore indicated within 72 hours after termination of pregnancy up to and including 12 weeks gestation. At or beyond 13 weeks gestation, a full 300 microgram dose of RHIG should be administered instead of a 50 microgram dose) .

The Colorado hospital does a fetal screen test when a patient requires at least a full 300 microgram dose of RHIG. They are considering dropping all testing for feto-maternal hemorrhage for patient between 13-26 weeks, even if a full 300 microgram dose of RHIG is indicated. After 26 weeks and post-partum they do a fetal screen to detect feto-maternal bleeds, in order to detect those bleeds that are sufficiently large to require additional vials of RHIG. The Colorado colleague wants to know what other colleague do in their practice regarding testing for feto-maternal bleeds and/or the use of micro versus full doses of RHIG?

Editor's note: In preparing replies to the Colorado colleague, members of the e-network forum might wish to review the previous discussion which may contain information that is germane to the current question.

The following responses were received.

ADDENDA May 8, 2003

1. According to a Consultant with the UK National Blood Service, the UK Guidelines are as follows:
   • up to 20 weeks gestation, a standard dose of 50 micrograms of RHIG is given and no Kleihauer test is done
   • after 20 weeks gestation, 100 micrograms of RHIG is given AND a Kleihauer test done to detect fetomaternal hemorrhage (FMH)
   • if the Kleihauer test reveals that the volume of red cells in an FMH exceeds 4 ml, this is confirmed by a second method, usually flow cytometry (a 24-hour service in England)
   • When the volume of red cells in a FMH is confirmed by flow cytometry to be greater than 4ml, additional anti-D is given (at 25 micrograms/ml of red cells) and the Kleihauer test repeated 72h later to demonstrate clearance of the fetal red cells (IM injections of anti-D take approximately 72 hours to reach a maximum blood level). When the FMH is very large, the IV rather than the IM route is used, and follow-up testing is done after 48 hours.
   A British Committee for Standards in Haematology (BCSH) Guideline pertaining to the above (Transfusion Medicine, 1999;9:87-92) can be accessed here.

ADDENDA Oct. 7, 2005

2. A colleague in a Sunbelt State wants to know what policy/practice others follow when screening blood of pregnant women for fetal red cells after the 20th week of gestation. She comments that according to the 23rd edition of AABB Standards 5.20.3 "There shall be a process to ensure that an adequate dose of Rh Immune Globulin is administered" and according to the 15th edition of the AABB Technical Manual (page 549) "at < 20 weeks, the fetal blood volume is rarely more than 30 mL, small enough that a single dose of 300 ug RHIG will be sufficient for prophylaxis for any feto-maternal hemorrhage. Therefore it is not necessary to quantitate fetal red cells in the maternal circulation before 20 weeks of gestation." She reports that her institution does not perform screening on maternal blood for fetal red cells for women who require RHIG before the 28th week of gestation.  She wonders if her institution should change its policy to screen maternal blood for fetal red cells for all ante-natal RHIG recipients who are at or beyond their 20th week of gestation.

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Ira A. Shulman, MD
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Elizabeth M. St. Lezin, MD
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