RHESUS HAEMOLYTIC DISEASE OF THE NEWBORN AND THE ABO GROUPS

Risk factors for RhD immunisation despite antenatal and postnatal anti-D prophylaxis

OBJECTIVE

To identify risk factors for Rhesus D (RhD) immunisation in pregnancy, despite adequate antenatal and postnatal anti-D prophylaxis in the previous pregnancy. To generate evidence for improved primary prevention by extra administration of anti-D Ig in the presence of a risk factor.

DESIGN

Case-control study.

SETTING

Nation-wide evaluation of the Dutch antenatal anti-D-prophylaxis programme.

POPULATION

CASES

42 RhD-immunised parae-1, recognised by first-trimester routine red cell antibody screening in their current pregnancy, who received antenatal and postnatal anti-D Ig prophylaxis (gifts of 1000 iu) in their first pregnancy.

CONTROLS

339 parae-1 without red cell antibodies.

METHODS

Data were collected via obstetric care workers and/or personal interviews with women.

MAIN OUTCOME MEASURE

Significant risk factors for RhD immunisation in multivariate analysis.

RESULTS

Independent risk factors were non-spontaneous delivery (assisted vaginal delivery or caesarean section) (OR 2.23; 95% CI:1.04-4.74), postmaturity (>or=42 weeks of completed gestation: OR 3.07; 95% CI:1.02-9.02), pregnancy-related red blood cell transfusion (OR 3.51; 95% CI:0.97-12.7 and age (OR 0.89/year; 95% CI:0.80-0.98). In 43% of cases, none of the categorical risk factors was present.

CONCLUSIONS

In at least half of the failures of anti-D Ig prophylaxis, a condition related to increased fetomaternal haemorrhage (FMH) and/or insufficient anti-D Ig levels was observed. Hence, RhD immunisation may be further reduced by strict compliance to guidelines concerning determination of FMH and accordingly adjusted anti-D Ig prophylaxis, or by routine administration of extra anti-D Ig after a non-spontaneous delivery and/or a complicated or prolonged third stage of labour.

[Prevention of fetal hemolytic disease: it is time to take action]

In spite of the progress made since 1970 in specific prevention by anti-rhesus immunoglobulins, and improved management of at-risk pregnancies, allo-immunization due to the erythrocytic Rh 1 antigen (formerly known as Rhesus D or Rh D) remains widespread. In fact, anti-Rh 1 antibodies currently constitute over one-third of the immune antibodies detected after pregnancy. The prevention of allo-immunization against the Rh 1 antigen is therefore still problematical, and concerns approximately one pregnant woman in seven. The etiology and pathology of fetal hemolytic disease have been recalled, and the treatment approach during pregnancy and delivery has been carefully examined. Tests for quantifying the risk of fetomaternal hemorrhage have also been described. This approach aims at improving the methods of preventing allo-immunization (e.g., during pregnancy and delivery) and the efficacy of treatment. It is also stated that if the necessary preventive action is not taken in cases of allo-immunization due to to the Rh 1 antigen, this should be considered a grave medical fault.

The decline in Rh hemolytic disease: should Rh prophylaxis get all the credit?

OBJECTIVES

This study sought to quantify the magnitude of Rh disease reduction occurring secondary to Rh prophylaxis and other determinants.

METHODS

Outcomes considered included maternal Rh sensitization, neonatal Rh disease, and perinatal deaths from Rh disease. Analysis was based on Poisson regression modeling of ecological data from Manitoba, Canada, and conditional probability modeling.

RESULTS

The ecological analysis showed that changes in birth order and Rh prophylaxis resulted in 24% (95% confidence interval [CI] = 1% 42%) and 69% (95% CI = 61%, 76%) decreases, respectively, in Rh sensitizations (D and non-D) in Manitoba between 1963 and 1988. Rh prophylaxis and nonprogram factors were responsible for 83% (95% CI = 44%, 95%) and 78% (95% CI = 42%, 91%), respectively, of the reduction in perinatal deaths from Rh disease. Similar results were obtained with conditional probability modeling, which also provided estimates for the effects of changes in abortion rates and racial composition.

CONCLUSIONS

In addition to Rh prophylaxis, changes in other determinants were responsible for an important fraction of the decline in Rh disease. These results provide a historical perspective on the conquest of Rh disease and also have important implications for public health policy, particularly in developing countries.

Relationship between Rh-o(D) zygosity and red cell Rh-o(D) antigen content in family members

The red cells of 63 members of 11 families were tested with (125)I-labeled anti-Rh(0)(D). Families with a history of hemolytic disease of the newborn due to fetomaternal Rh incompatibility were selected for study. In such families it was possible to determine the antibody binding to the Rh(0)(D) heterozygous red cells of the children and to compare within each family this value with the antibody bound to the father's Rh(0)(D)-positive red cells and the mother's Rh(0)(D)-negative red cells. The fathers in all the families studied could be assigned to two classes on the basis of the quantity of antibody bound to their red cells. One group bound about the same quantity of antibody to their cells as did their children, indicating that they were heterozygous for the Rh(0)(D) antigen. The other bound about twice as much antibody to their cells as did their children, indicating that they were homozygous for the antigen. The Rh genotype of the father in all 11 families could be ascertained by using the children in each family as a reference point. The members of two families showed a poor correspondence between antibody binding and zygosity. In one family an Rh heterozygous child (R(1)r) took up 85% of the antibody bound to the father's homozygous cells (R(1)R(1)), and in the other family an Rh heterozygous child (R(1)r) took up 20% more antibody than did the cells of her father, which were of the same Rh phenotype (Rh(1)) and zygosity.The quantity of antibody bound to the red cells of unrelated Rh(0)(D) homozygous individuals of the same Rh phenotype (Rh(1)) showed an almost sixfold variation. A consequence of this observation was that the cells of Rh(0)(D) heterozygous children of high antibody uptake fathers took up more antibody than did the cells of low antibody uptake Rh(0)(D) homozygous fathers. The gene dosage effect for the Rh(0)(D) antigen demonstrable within a family does not appear to apply when unrelated individuals are tested, even though they may be of the same Rh phenotype.