|
|
 |
 |
 |
|
|
|||
|
||||
|
||||
Re: ACOG Rh antibody testing--whoaFrom: MNudel@aol.comFri Sep 20 00:50:57 1996
I believe that these recommendations are being misinterpreted by listers. My interpretation is that these recommendations are for following the patient (who is antibody positive) with titers. This can be done until the titers reach >1:8. I include the text of the ACOG bulletin for your own interpretation. Mitch Nudelman FACOG CLINICAL MANAGEMENT Once it has been established that a pregnant woman is sensitized to an antigen that may cause erythroblastosis, the genotype of the fetus's father should be determined. This is most useful for the atypical antigens because iso-immunization is often secondary to a transfusion. If the father of the fetus does not possess the antigen, the fetus is not at risk. If the father is a heterozygote there is only a 50% chance that the fetus has inherited the blood group antigen and the pregnancy is affected. The most likely zygosity for the D antigen can also be predicted as the alleles at the C, D, and E loci are inherited together, and some combinations are more frequent than others. Because it is not possible to test for the presence of D antigens, zygosity can be determined only by looking at the combination. Clinically, however, determining this genotype is of limited value for the couple receiving counseling after a severely affected pregnancy. Unless the D-positive partner has previously fathered a D-negative child, it is impossible to state with certainty that he is a heterozygote. Antibody Titers Maternal serum antibody titers can be measured by a variety of techniques (4). Agglutination of erythrocytes in saline measures maternal IgM antibody, and this is too large a molecule to cross the placenta. Albumin is a more viscous medium; therefore, the smaller IgG molecules are capable of agglutinating erythrocytes, but the contribution by IgM is not eliminated. The most sensitive and accurate barometer for clinical practice is the indirect Coombs test. The usefulness of maternal serum antibody titers is determined by the patient's reproductive history. If a pa-tient has never had a pregnancy complicated by Rh-related neonatal morbidity other than hyperbilirubinemia treated by phototherapy, antibody titers are the initial step of management. An antibody titer should be determined at the first prenatal visit, at 20 weeks of gestation, and approximately every 4 weeks thereafter. When the antibody titer is 1:8, whether directed to D or another paternal antigen capable of causing severe erythroblastosis, no intervention is necessary; when the titer is 1:16 in albumin or 1:32 by indirect antiglobulin (indirect Coombs test), amniocentesis or percutaneous umbilical cord blood sampling (cordocentesis) should be considered (5).
|
|
Return to
|
Mail a New Message to the Forum: ob-gyn-l@obgyn.net Forum Administrator: geffrey.klein@obgyn.net Report Technical Problems: webmaster@obgyn.net Last Updated: Wed Dec 2 05:17:17 2009 |
The American Medical Association is no longer designating CME hours for AMA Category II CME credit. However, physicians themselves may self designate learning activities as Category II CME credit hours if they feel it is of sufficient educational merit and meets the formal definitions of continuing medical education. OBGYN.net believes these interaction in this forum meets these criteria. For further information see the AMA web site.