A transfusion medicine colleague in Barcelona has recently been asked by a local obstetrician why it was necessary to administer RhIg immunoprophylaxis to a pregnant Rh(D) negative woman who is not alloimmunized and whose husband is Rh(D) negative. The husband's Rh-negative status was determined using the GEL method; a tube test for 'weak D' was not performed. The Spanish colleague wonders how colleagues would deal with this situation, specifically:

• What would you tell the obstretician?
• Would you recommend that this women receive RhIg because you assume that the husband might NOT be the biological father?
• Alternatively, if you think that he might be the biological father, do you not trust the test results that say he is Rh negative? (We do not know if the father's Rh type is based on a single specimen's test results, or if he has been typed on more than one occasion using more than one blood sample.)
• Are there other considerations?

The Spanish colleague points out that in his jurisdiction, standard RhIg recommendations do not take into account a husband's Rh(D) status.

The following comment has been received.

ADDENDA June 30, 2004

1. A colleague in Texas is of the opinion that sometimes discretion is the best strategy. If the decision to not admister RHIG to a pregnant Rh negative woman was to be based on her partner's Rh type, at a minimum her facility would test the alleged father for D and weak D, and then repeat the Rh typing scheme on a second, separately drawn specimen. However, even that procedure would not account for possible indiscretions of the mother. In her opinion, the incidence of the husband not being the father is rare, but it does happen. She does not believe it is the obstetrician's responsibility to delve into this very touchy subject. If the woman is always offered Rh immunoprophylaxis, future pregancies are protected. If the patient insists on stipulating her Rh immunoprophylaxis based on the Rh type of her sexual partner, the Texan would have them both sign a disclaimer, holding the physician blameless for not administering Rh Immune Globulin, in the event the sexual partner typed Rh negative.

ADDENDA Aug. 18, 2004

2. A medical director of a moderate-sized blood collection and transfusion service in the Midwest recently encountered a similar problem. An obstetrician was following the pregnancy of an Rh negative, non-immunized woman. At the last office visit, the patient turned up at the doctor's office with a laboratory report indicating that her husband was also Rh negative, and on this basis she refused RhIg. The obstetrician was perplexed and asked for advice. Both the OB and the responding medical director agreed that it was appropriate to give RhIg to an Rh negative pregnant woman, regardless of the serologic test results of the named father. The OB was advised to discuss the issue with the patient, and let her know that the Rh system is genetically complex. There are rare circumstances where expected Rh red cell antigens of the father could be missing or suppressed, and that routine Rh testing can infrequently miss some of the antigens that are present, such that a 'false Rh negative' test result was possible. A single routine Rh test was not sufficient to completely exclude the possibility that the husband could pass on an Rh positive blood type to his child. The sure and safe approach, especially if the couple planned to have more than one child, was to give the RhIg. The obstetrician relayed this information to the patient and her family in a brief and factual way, completely removing the potentially explosive "Is he or is he not the father" issue from the discussion. The patient then accepted the proposed treatment plan, including the RhIg. To support the aforementioned strategy the responding colleague offered the following reference : Rossi's Principles of Transfusion Medicine, 3rd Edition.

ADDENDA Sept. 17, 2004

3. A colleague in Virginia reports that at her facility a potential transfusion candidate is called Rh negative when the patient is typed with anti-D reagent and there is a 1+ or weaker reaction. However, she wishes to caution others of a scenario that recently developed regarding prophylactic doses of RHIG for expectant mothers, when the unborn baby's 'father' was called Rh negative, but actually had a weak expression of the D-antigen. Apparently it has been a policy of many local obstetricians in her community to not administer prophylactic RHIG during a mother's pregnancy if there is 'proof' that a 'father' is Rh negative. A situation occurred at her facility in which a 'father' had 'proof' from his military records that he was Rh negative. Consequently , the mother did NOT receive RHIG based on this information. Upon the birth of the child, the cord blood proved to be 2+ positive with anti-D, and therefore the neonate was determined to be Rh positive. When the mother was told of her need for RHIG, both she AND her husband were very upset at the "obvious" mistake. When testing of the neonate was repeated and it was confirmed that the neonate was Rh positive, the father then questioned his paternity. The father then had his ABO/Rh determined, and his red cells reacted 1+ with anti-D, which according to the Virginia hospital's policy, would make the father Rh negative. However, considering the situation, the blood bank contaced the ordering doctor and explained that the father appeared to have a weak expression of D. The OB/GYN physicians called a meeting the following morning with the Blood Bank to understand and establish new policies in the administration of Rhogam to their patients. The Virginian wonders what others' views are on this?

(Editor's note: It seems prudent to limit a policy that allows an individual to be called Rh negative based on weak reactive results with anti-D to transfusion recipients. It is NOT prudent to apply such a policy to blood donors or husbands/partners of pregnant Rh women. As the above case illustrates, calling the father Rh negative based on this criterion will result in a decision not to administer RHIG immunoprophylaxis to an Rh negative pregnant woman who might be at risk of anti-D immunization.]

ADDENDA Sept. 29, 2004

4. A transfusion medicine physician in Barcelona reports that at his institution, in order to address the problem of an Rh(D) negative woman who declares that her husband is also Rh negative, they have started to genotype the Rh(D) status of the fetus using a sample of plasma of the mother to detect the RHD sequence. Using a real-time PCR assay this can be done as early as the 12th week of pregnancy. As a control they use the amplification of the Y chromosome associated SRY gene so that they can also inform the parents of the sex of the fetus, if they wish to know. Using this approach the Barcelona physician estimates they are able to avoid giving RhIg to Rh(D) negative women in about 40% of the cases.

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Ira A. Shulman, MD
CBBS e-Network Forum Editor & Moderator