Predicting severe disease in the second pregnancy with RhD antibodies
The association between severity in the first and the second pregnancy with RhD antibodies was assessed in both subgroups. In group A, 5/11 (45%) women with moderate to severe disease in the first pregnancy with RhD immunization developed severe disease in the second pregnancy as compared to 1/16 women with previous no or mild disease (6%, OR 12.5, 95% CI 1.2-130.6, P =.027). In group B, this was 5/8 (63%) as compared to 7/17 women with previous no or mild disease (41%, OR 2.4, 95% CI 0.4-13.4, P =.411).
Factors from the first immunized pregnancy possibly predicting severe disease in the subsequent pregnancy with a RhD-positive foetus were assessed in a multivariate prediction model per subgroup (supplemental Table S4). In group A, the highest ADCC result in the first immunized pregnancy remained as the only factor associated with severe disease in the subsequent pregnancy. The predictive value of this test is summarized in Table S5. The negative predictive value of an ADCC test result >10% appeared most useful: if the ADCC test did not exceed 10% in the first pregnancy, 89% (95% CI 55-98%) of subsequent RhD-positive children will not be treated with intrauterine transfusion(s).
In group B, no predictive factors were found in this multivariate analysis.
DISCUSSION