Fetomaternal hemorrhage: incidence, risk factors, time of occurrence, and clinical effects.

Most women have only very small amounts of fetal blood in their circulations following pregnancy and delivery: the volume is less than 0.5 mL of whole blood in 93 percent of women, less than 1 mL in 96 percent, and less than 2 mL in 98 percent. FMH of 30 mL or more occurs in just 3 of 1000 women. When the FMH was 150 mL or more, 15 of 41 infants did not survive Rh-negative women with FMH of more than 30 mL of Rh-positive whole blood are at increased risk of Rh immunization, and thus the outcome of their future pregnancies also may be affected. ABO-compatible fetal red cells that have entered the maternal circulation have a life span similar to that of adult cells. ABO-incompatible fetal red cells may be cleared rapidly, but in some cases they circulate for weeks. Most FMHs of 30 mL or more occur before labor, delivery, or cesarean section. The majority occur with minimal clinical signs and symptoms in apparently normal pregnancies. The identification of postpartum Rh-negative women who have 30 mL or more of Rh-positive fetal blood in their circulation is important so that sufficient RhIG for immune suppression can be administered. It appears that more than one-half of women with FMH of 30 mL or more would not be identified if protocols were adopted to test only women in pregnancies considered to be at high risk.

Gm allotyping to determine the origin of red cell antibodies in recipients of solid organ transplants.

Alloantibodies of A and B specificity were detected in the serum and on the red cells of 4 non-0 recipients of group 0 solid organ transplants. The antibodies were assumed to be produced by 'passenger' lymphocytes introduced at the time of transplant. Gm allotyping of donor serums, recipient serums and the unexpected antibodies was done. Gm typing was informative in 1 case, when the anti-A1 found in the serum of a liver transplant recipient was shown to be of phenotype Gm(fb) and the Gm phenotype of the recipient to be Gm(axg). Gm allotyping was not informative in the other 3 cases.

Detection of fetal hemorrhage in Rh immune globulin candidates. A rosetting technique using enzyme-treated Rh2Rh2 indicator erythrocytes.

Current serologic tests occasionally fail to identify women needing more than one vial of Rh immune globulin. We compared the indirect antiglobulin test after incubation with anti-D and a rosetting technique using enzyme treated Rh2Rh2 erythrocytes as methods for identifying significant fetal maternal hemorrhage (FMH). Artificial mixtures containing 0.05 to 1.2 percent Rh1rh (CcDe) fetal red blood cells mixed with rh (ce) adult red blood cells were tested. The indirect antiglobulin test of the 0.6 percent mixture (approximately 30 ml FMH) was reported to be microscopically positive by 17/20 technologists; whereas, 20/20 found the rosetting test to be strongly positive. The volume of FMH in 118 postpartum Rh immune globulin candidates was quantified using Kleihauer's test and formula. The results of the rosetting and Kleihauer tests of blood specimens from these patients were negative 1.4 ml for two, and strongly positive rosetting test and FMH of 6.5 ml for one. The rosetting test utilizes routine blood banking skills and requires 5 minutes more "hands on" time than an indirect antiglobulin test. Confirmation and quantification of positive results by an acid-elution test is necessary.

Evaluation of methods for detection and quantitation of fetal cells and their effect on RhIgG usage.

A 1980 College of American Pathologists Immunohematology Survey included two erythrocyte suspensions, one with and one without fetal cells, designed to evaluate methods for detecting and quantitating fetomaternal hemorrhage in Rh immune globulin candidates. Data from a supplementary questionnaire regarding Rh immune globulin administration during 1979 were compared by methods used. The most commonly used screening test was the microscopic Du. With this test, 12.2% of nearly 2,000 laboratories obtained a false negative result on an unknown which contained approximately 0.6% Rh positive erythrocytes. On this 100% adult cell suspension two-thirds of laboratories using acid elution technics reported the presence of fetal cells. Laboratories using Fetaldex to screen for and quantitate fetomaternal hemorrhage had the highest rate of false positives on this unknown and reported higher rates of multiple vial Rh immune globulin administration when compared to institutions using other acid elution procedures. The second unknown in this survey contained approximately 0.4% fetal cells. About one third of laboratories, using each of four acid elution technics, reported values less than one half to more than twice this amount. The number of false positive and false negative results and the wide scatter of quantitation amounts reported for these two unknowns suggest that better methods are needed for screening and quantitating fetomaternal hemorrhage.

Comparison of fetomaternal hemorrhage detection methods and Rh immune globulin usage.

A 1977 College of American Pathologists survey of hospitals has been analyzed to compare Rh immune globulin usage (RhIgG) with methods used to screen and confirm fetomaternal hemorrhage (FMH). The survey data show that there is a correlation between the rate of multiple vial usage and the confirmation method used. Laboratories using Fetaldex administered multiple vials of Rh immune globulin significantly more often than laboratories using other acid elution technics. This difference was independent of the screening methods used and was not related to the number of patients tested in laboratories giving fewer than 300 vials of Rh immune globulin per year. The incidence of fetomaternal hemorrhages of greater than 30 ml has been reported to be 0.3% by various groups using Kleihauer procedures to test large numbers of women after delivery. In 61 of 374 laboratories using Fetaldex and 15 of 253 laboratories using Kleihauer-Betke procedure more than ten times the expected number of recipients were given multiple vials.

Gm and Km allotypes in disputed parentage.

Immunoglobulin allotyping in 925 cases of disputed paternity provided evidence of exclusion for 70 alleged fathers. Combining results from erythrocytic antigen, enzyme, and serum protein tests, 230 men were proven to be falsely accused; in 15 cases the immunoglobulin allotype provided the only evidence for exclusion, in 67 no exclusion would have been identified if testing had been limited to ABO, Rh, and MNSs. Various cases in this study illustrate the importance of using an extensive battery of immunoglobulin reagents in order maximally to exclude falsely accused men, and to identify infrequent haplotypes, which might erroneously be interpreted as indirect exclusions or may indicate a high likelihood of paternity. The problems of Gm typing of very young children are described. When child is less than 6 months of age, direct exclusions may be missed by the Gm allotypes; indirect exclusions are valid only when the phenotype differs from that of the mother. Km allotypes are not age-dependent.