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Rhesus isoimmunization: increased hemolysis during early infancy
M Hayde1, J A Widness, A Pollak
1Department of Neonatology, University Children's Hospital, Vienna, Austria.
Insights
In infants with severe Rh isoimmune hemolytic disease, elevated carboxyhemoglobin (COHb) and bilirubin levels indicate ongoing hemolysis due to persistent maternal Rh antibodies.
Area of Science:
- Neonatal Medicine
- Hematology
- Immunology
Background:
- Hemolytic disease of the newborn is a serious condition.
- Rh isoimmune hemolytic disease requires careful monitoring of hemolysis indicators.
Purpose of the Study:
- To investigate elevated carboxyhemoglobin (COHb) and plasma bilirubin in infants with Rh isoimmune hemolytic disease.
- To assess these hemolysis indicators during the first three months of life.
Main Methods:
- Serial blood samples were collected from infants with Rh isoimmune hemolytic disease, ABO hemolytic disease, and controls.
- Measurements included COHb, plasma bilirubin, hemoglobin, reticulocyte count, erythropoietin, enzymes, and iron.
- Statistical comparisons were made between groups.
Main Results:
- Infants with Rh isoimmune hemolytic disease showed significantly lower Hb and higher bilirubin, COHb/Hb ratio, and erythropoietin at 2 and 6 weeks.
- COHb/Hb and plasma bilirubin were significantly correlated in the Rh-immunized group.
- Maternal Rh antibodies had a mean half-life of 14.3 days in affected neonates.
Conclusions:
- Elevated bilirubin and COHb/Hb in early life suggest ongoing hemolysis in Rh isoimmune hemolytic disease.
- Persistence of maternal Rh antibodies is implicated as the cause of continued hemolysis.
Abstract:
The objective of the present study was to determine whether whole blood carboxyhemoglobin (COHb) and plasma bilirubin, two indicators of hemolysis, are elevated in infants with severe Rh isoimmune hemolytic disease during the first months of life. Beginning at 2 wk of age and continuing monthly for 3 mo, serial blood samples were obtained for COHb, plasma bilirubin, Hb, reticulocyte count, plasma erythropoietin, plasma enzymes, and plasma iron. Because control infants (n = 13) and infants with ABO hemolytic disease (n = 5) did not differ from one another in any of the study parameters, these two groups were combined and compared with infants with the Rh isoimmunization. Infants with severe Rh isoimmune hemolytic disease (n = 13) were found to have significantly lower Hb and significantly higher bilirubin, the COHb fraction divided by the Hb concentration (COHb/Hb), and plasma erythropoietin levels at 2 and 6 wk of age, and reticulocyte counts at 6 wk. The remaining parameters were not different between the control-ABO group and Rh-isoimmune group at any of the study intervals. The study's two primary indicators of hemolysis, plasma bilirubin and COHb/Hb, were significantly correlated with one another in the Rh-immunized group (r = 0.66, p < 0.0001), but not in the combined control-ABO group. Serial Rh antibody concentrations measured in the serum of four neonates with Rh isoimmunization demonstrated a mean half-life of 14.3 d. We speculate that, among infants with severe Rh isoimmune hemolytic disease, elevated total bilirubin levels and COHb/Hb ratios identified in the early weeks of life indicate continuing hemolysis due to persistence of maternal Rh antibodies.