Red blood cell alloimmunization prevalence and hemolytic disease of the fetus and newborn in Israel: A retrospective study

Neonatal and Obstetrical Outcomes of Pregnancies Complicated by Alloimmunization

BACKGROUND AND OBJECTIVES

Despite advances in the prevention of rhesus (Rh)(D) alloimmunization, alloantibodies to Rh(D) and non-Rh(D) red blood cell antigens continue to be detected in ∼4% of US pregnancies and can result in hemolytic disease of the fetus and newborn (HDFN). Recent reports on HDFN lack granularity and are unable to provide antibody-specific outcomes. The objective of this study was to calculate the frequency of alloimmunization in our large hospital system and summarize the outcomes based on antibody specificity, titer, and other clinical factors.

METHODS

We identified all births in a 6-year period after a positive red blood cell antibody screen result during pregnancy and summarized their characteristics and outcomes.

RESULTS

A total of 707 neonates were born after a positive maternal antibody screen result (3.0/1000 live births). In 31 (4%), the positive screen result was due to rhesus immune globulin alone. Of the 676 neonates exposed to alloantibodies, the direct antibody test (DAT) result was positive, showing antigen-positivity and evidence of HDFN in 37% of those tested. Neonatal disease was most severe with DAT-positive anti-Rh antibodies (c, C, D, e, E). All neonatal red blood cell transfusions (15) and exchange transfusions (6) were due to anti-Rh alloimmunization. No neonates born to mothers with anti-M, anti-S, anti-Duffy, anti-Kidd A, or anti-Lewis required NICU admission for hyperbilirubinemia or transfusion.

CONCLUSIONS

Alloimmunization to Rh-group antibodies continues to cause a majority of the severe HDFN cases in our hospital system. In neonates born to alloimmunized mothers, a positive DAT result revealing antigen-positivity is the best predictor of anemia and hyperbilirubinemia.

The influence of HLA allele and haplotype on RhE alloimmunization among pregnant females in the Chinese Han population

BACKGROUND AND OBJECTIVES

Anti-E alloantibody is the most common and important red blood cell (RBC) alloantibody during pregnancy. The study aimed to determine the correlation between RhE alloimmunization and human leukocyte antigen (HLA) allele polymorphism, as well as haplotype diversity, among pregnant individuals in the Chinese Han population.

STUDY DESIGN AND METHODS

All individuals included in our study were RhE-negative pregnant women of Chinese Han ethnicity, confirmed through serological testing. Pregnancy could be the only potential stimulating factor in RBC alloimmunization. Given the serological testing, the participants were divided into anti-E (responders) and non-anti-E-producing group (non-responders). The class I and II classical HLA genotyping were determined using next-generation sequencing, and the HLA genotype and haplotype frequencies were compared between the responders and non-responders.

RESULTS

In total, 76 responders and 94 non-responders were enrolled in this study. Comparison results showed that all HLA class I alleles had no difference between the two groups. For HLA class II phenotypes, responders had higher frequencies of HLA-DRB1*09:01, HLA-DQA1*03:02 and HLA-DQB1*03:03 phenotypes than non-responders, and the differences were statistically significant (pc < 0.05). In addition, the haplotype frequency of HLA-DRB1*09:01-DQA1*03:02-DQB1*03:03 in the RhE responders was significantly higher than in the non-responders (31.58% vs. 12.77%; odds ratio, 3.154; 95% confidence interval, 1.823-5.456; pc value, 1.25 × 10-3).

CONCLUSION

Our findings indicated that HLA-DRB1*09:01, HLA-DQA1*03:02 and HLA-DQB1*03:03 might be susceptible alleles for RhE alloimmunization among Chinese Han pregnant females. These three susceptible alleles constituted the unique three-locus haplotype in the RhE responders and collaborated to RhE alloimmunization.

Non-RhD alloimmunization in pregnancy: an updated review

RhD alloimmunization in pregnancy is still the main cause of hemolytic disease of the fetus and neonate (HDFN). Nevertheless, there are other antigens that may be associated with the occurrence of this phenomenon and that have been growing in proportion, given that current prevention strategies focus only on anti-RhD antibodies. Although not widespread, the screening and diagnostic management of the disease caused by these antibodies has recommendations in the literature. For this reason, the following review was carried out with the objective of listing the main red blood cell antigen groups described - such as Rh, ABO, Kell, MNS, Duffy, Kidd, among others - addressing the clinical importance of each one, prevalence in different countries, and recommended management when detecting such antibodies during pregnancy.

Another piece of the hemolytic disease of the fetus and newborn puzzle after RhD-positive transfusion in trauma resuscitation: the proportion of pregnant women who produce high titer anti-D

Background

After the transfusion of RhD-positive red blood cell (RBC)-containing products to an RhD-negative woman of childbearing potential (WCP) during trauma resuscitation, there are several events that must occur for that WCP to have a future pregnancy affected by hemolytic disease of the fetus and newborn (HDFN). This study identified and quantitated the frequency of a novel event in the sequence from RhD-positive transfusion during trauma resuscitation to an HDFN outcome, that is, the development of a high titer anti-D among women who were D-alloimmunized.

Methods

The transfusion service records at one maternity hospital were searched to locate all anti-D titers that had been performed on pregnant women between 1996 and 2022. The highest titer score during each pregnancy was recorded for this study. The critical titer threshold at this institution was ≥16. Passive anti-D caused by Rh immunoglobulin were excluded from analysis.

Results

There were 97 pregnancies in 85 patients who had an immune-stimulated anti-D; in 60 of 97 (62%) pregnancies, the highest titer score was ≥16. There were 12 patients who had titers performed in two pregnancies during the study period; the correlation between the maximum titer in each pregnancy was not statistically significant (Spearman rank correlation r=0.42, p=0.17).

Conclusion

In this single center study, 62% of D-alloimmunized pregnant women had a high titer antibody. When considering all of the events that must occur for HDFN to happen, the rate of perinatal mortality was calculated to be 0.04% and the rate of perinatal death or serious adverse event from HDFN was 0.24%.

Live birth prevalence of hemolytic disease of the fetus and newborn in the United States from 1996 to 2010

BACKGROUND

Hemolytic disease of the fetus and newborn (HDFN) is mediated by maternal alloantibodies, a consequence of immune sensitization during pregnancy with maternal-fetal incompatibility with ABO, Rhesus factor (Rh), and/or other red blood cell antigens. RhD, Kell, and other non-ABO alloantibodies are the primary cause of moderate to severe HDFN, whereas ABO HDFN is typically mild. HDFN live birth prevalence owing to Rh alloimmunization among newborns in the United States was last estimated to be 106 per 100,000 births in 1986. HDFN live birth prevalence owing to all alloantibodies was estimated to be 817 to 840 per 100,000 in Europe. There is a need for updated prevalence estimates in the United States and a better understanding of disease demographics, severity, and treatments.

OBJECTIVE

This study aimed to estimate the live birth prevalence of HDFN and the proportion of severe cases of HDFN in the United States, to describe the associated risk factors, and to compare the clinical outcomes and treatments among healthy newborns, newborns with HDFN, and newborns who are sick without HDFN using a nationally representative hospital discharge database.

STUDY DESIGN

In this retrospective, observational cohort study, we used data from the 1996 to 2010 National Hospital Discharge Survey to identify live births, defined by inpatient visits with the newborn flag, with and without a diagnosis of HDFN across 200 to 500 sampled hospitals (≥6 beds) per year. Patient and hospital characteristics, alloimmunization status, disease severity, treatment, and clinical outcomes were evaluated. Frequencies and weighted percentages were calculated for all variables. Logistic regression was used to compare the characteristics between newborns with HDFN and other newborns using odds ratios.

RESULTS

Of 480,245 live births identified, 9810 HDFN cases were recorded. When weighted to the United States population, this corresponded to a live birth prevalence of 1695 per 100,000 live births. Compared with other newborns, newborns with HDFN were more likely to be female, Black, living in the South (vs the Midwest or West), and treated at larger (>100 beds) and government-owned hospitals. ABO and Rh alloimmunization accounted for 78.1% and 4.3% of newborns with HDFN, respectively, whereas HDFN caused by other antigens, such as Kell and Duffy, accounted for 17.6% of the cases. Among newborns with HDFN, 22% received phototherapy, 1% received simple transfusions, and 0.5% received exchange transfusions or intravenous immunoglobulin. Newborns affected by HDFN caused by Rh alloimmunization were more likely to require medical interventions, including simple or exchange transfusions, and more likely to be delivered by cesarean delivery. Overall, HDFN was associated with a longer hospital length of stay in the neonatal intensive care unit when compared with healthy and other sick newborns, a higher rate of cesarean delivery, and a higher rate of nonroutine discharge than healthy newborns.

CONCLUSION

Overall, the live birth prevalence of HDFN was higher than those previously reported, whereas Rh-induced HDFN live birth prevalence was similar to those previously reported. HDFN live birth prevalence owing to Rh alloimmunization decreased over time, likely because of continued Rh immune globulin prophylaxis. Treatment patterns for newborns with HDFN and the comparative clinical outcomes when compared with healthy newborns confirm the continued clinical needs of this population.

Hemolytic disease of the fetus and newborn: systematic literature review of the antenatal landscape

BACKGROUND

Prevention of pregnancy-related alloimmunization and the management of hemolytic disease of the fetus and newborn (HDFN) has significantly improved over the past decades. Considering improvements in HDFN care, the objectives of this systematic literature review were to assess the prenatal treatment landscape and outcomes of Rh(D)- and K-mediated HDFN in mothers and fetuses, to identify the burden of disease, to identify evidence gaps in the literature, and to provide recommendations for future research.

METHODS

We performed a systematic search on MEDLINE, EMBASE and clinicaltrials.gov. Observational studies, trials, modelling studies, systematic reviews of cohort studies, and case reports and series of women and/or their fetus with HDFN caused by Rhesus (Rh)D or Kell alloimmunization. Extracted data included prevalence; treatment patterns; clinical outcomes; treatment efficacy; and mortality.

RESULTS

We identified 2,541 articles. After excluding 2,482 articles and adding 1 article from screening systematic reviews, 60 articles were selected. Most abstracted data were from case reports and case series. Prevalence was 0.047% and 0.006% for Rh(D)- and K-mediated HDFN, respectively. Most commonly reported antenatal treatment was intrauterine transfusion (IUT; median frequency [interquartile range]: 13.0% [7.2-66.0]). Average gestational age at first IUT ranged between 25 and 27 weeks. weeks. This timing is early and carries risks, which were observed in outcomes associated with IUTs. The rate of hydrops fetalis among pregnancies with Rh(D)-mediated HDFN treated with IUT was 14.8% (range, 0-50%) and 39.2% in K-mediated HDFN. Overall mean ± SD fetal mortality rate that was found to be 19.8%±29.4% across 19 studies. Mean gestational age at birth ranged between 34 and 36 weeks.

CONCLUSION

These findings corroborate the rareness of HDFN and frequently needed intrauterine transfusion with inherent risks, and most births occur at a late preterm gestational age. We identified several evidence gaps providing opportunities for future studies.