Red cell alloimmunization: A 2020 update

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.

Use of Low-Titer O-Positive Whole Blood in Female Trauma Patients: A Literature Review, Qualitative Multidisciplinary Analysis of Risk/Benefit, and Guidelines for Its Use as a Universal Product in Hemorrhagic Shock

BACKGROUND

Whole blood transfusion is associated with benefits including improved survival, coagulopathy, and decreased transfusion requirements. The majority of whole blood transfusion is in the form of low-titer O-positive whole blood (LTOWB). Practice at many trauma centers withholds the use of LTOWB in women of childbearing potential due to concerns of alloimmunization. The purpose of this article is to review the evidence for LTOWB transfusion in female trauma patients and generate guidelines for its application.

STUDY DESIGN

Literature and evidence for LTOWB transfusion in hemorrhagic shock are reviewed. The rates of alloimmunization and subsequent obstetrical outcomes are compared to the reported outcomes of LTOWB vs other resuscitation media. Literature regarding patient experiences and preferences in regards to the risk of alloimmunization is compared to current trauma practices.

RESULTS

LTOWB has shown improved outcomes in both military and civilian settings. The overall risk of alloimmunization for Rhesus factor (Rh) - female patients in hemorrhagic shock exposed to Rh + blood is low (3% to 20%). Fetal outcomes in Rh-sensitized patients are excellent compared to historical standards, and treatment options continue to expand. The majority of female patients surveyed on the risk of alloimmunization favor receiving Rh + blood products to improve trauma outcomes. Obstetrical transfusion practices have incorporated LTOWB with excellent results.

CONCLUSIONS

The use of whole blood resuscitation in trauma is associated with benefits in the resuscitation of severely injured patients. The rate at which severely injured, Rh-negative patients develop anti-D antibodies is low. Treatments for alloimmunized pregnancies have advanced, with excellent results. Fears of alloimmunization in female patients are likely overstated and may not warrant the withholding of whole blood resuscitation. The benefits of whole blood resuscitation likely outweigh the risks of alloimmunization.

Immunologic aspects of preeclampsia

Preeclampsia is a syndrome with multiple etiologies. The diagnosis can be made without proteinuria in the presence of dysfunction of at least 1 organ associated with hypertension. The common pathophysiological pathway includes endothelial cell activation, intravascular inflammation, and syncytiotrophoblast stress. There is evidence to support, among others, immunologic causes of preeclampsia. Unlike defense immunology, reproductive immunology is not based on immunologic recognition systems of self/non-self and missing-self but on immunotolerance and maternal-fetal cellular interactions. The main mechanisms of immune escape from fetal to maternal immunity at the maternal-fetal interface are a reduction in the expression of major histocompatibility complex molecules by trophoblast cells, the presence of complement regulators, increased production of indoleamine 2,3-dioxygenase, activation of regulatory T cells, and an increase in immune checkpoints. These immune protections are more similar to the immune responses observed in tumor biology than in allograft biology. The role of immune and nonimmune decidual cells is critical for the regulation of trophoblast invasion and vascular remodeling of the uterine spiral arteries. Regulatory T cells have been found to play an important role in suppressing the effectiveness of other T cells and contributing to local immunotolerance. Decidual natural killer cells have a cytokine profile that is favored by the presence of HLA-G and HLA-E and contributes to vascular remodeling. Studies on the evolution of mammals show that HLA-E, HLA-G, and HLA-C1/C2, which are expressed by trophoblasts and their cognate receptors on decidual natural killer cells, are necessary for the development of a hemochorial placenta with vascular remodeling. The activation or inhibition of decidual natural killer cells depends on the different possible combinations between killer cell immunoglobulin-like receptors, expressed by uterine natural killer cells, and the HLA-C1/C2 antigens, expressed by trophoblasts. Polarization of decidual macrophages in phenotype 2 and decidualization of stromal cells are also essential for high-quality vascular remodeling. Knowledge of the various immunologic mechanisms required for adequate vascular remodeling and their dysfunction in case of preeclampsia opens new avenues of research to identify novel biological markers or therapeutic targets to predict or prevent the onset of preeclampsia.

Automated quantitative evaluation of fetal atrioventricular annular plane systolic excursion before and after intrauterine blood transfusion in pregnancies affected by red blood cell alloimmunization

INTRODUCTION

Maternal red blood cell alloimmunization during pregnancy can lead to hemolysis and various degrees of fetal anemia, which can be treated with intrauterine blood transfusion (IUT) to prevent adverse outcomes. Knowledge about fetal myocardial function and adaptation is limited. The aim of the present study was to measure fetal atrioventricular plane displacement before and after IUT and compare these measurements with previously established reference ranges.

MATERIAL AND METHODS

An observational study was conducted on pregnant women affected by red blood cell alloimmunization. Fetal echocardiography was performed before and after IUT. The atrioventricular plane displacement of the left and right ventricular walls and interventricular septum, described as mitral, septal, and tricuspid annular plane systolic excursion (MAPSE, SAPSE, and TAPSE, respectively), was assessed using color tissue Doppler imaging with automated analysis software. A Mann-Whitney U test was used to compare the z scores to the normal mean before and after IUT.

RESULTS

Twenty-seven fetuses were included. The mean z score for pre-IUT MAPSE was significantly increased compared with the reference ranges, +0.46 (95% confidence interval [CI] +0.17 to +0.75; p = 0.039), while the mean z scores for post-IUT SAPSE and TAPSE were significantly decreased, -0.65 (95% CI -1.11 to -0.19; p < 0.001) and -0.60 (95% CI -1.04 to -0.17; p = 0.003), respectively. The difference in atrioventricular plane displacement z scores before and after IUT was statistically significant in all three locations. The median difference between the pre-IUT and post-IUT z scores was -0.66 (95% CI -1.03 to -0.33, p < 0.001) for MAPSE, -1.05 (95% CI -1.43 to -0.61, p < 0.001) for SAPSE, and -0.60 (95% CI -1.19 to -0.01, p = 0.046) for TAPSE.

CONCLUSIONS

This study suggests that atrioventricular plane displacement, when determined using automated analysis software, may represent a quantitative parameter, describing fetal myocardial function and adaptation before and after IUT.

Liver Dysfunction with Severe Cholestasis and Coagulation Disorders in the Course of Hemolytic Disease of the Newborn Requiring Chelation Therapy-A Case Report and Review of the Literature

Severe hemolytic disease of the fetus and newborn (HDFN) requiring intrauterine transfusions (IUTs) may cause iron accumulation, resulting in liver damage, which may lead to cholestasis and coagulation disorders. In this article, we reported a case of a female neonate who underwent chelation therapy with a positive outcome, and we reviewed the English and Polish literature on chelation therapy in HDFN available in PubMed. The patient with maximum ferritin concentration above 33,511.2 ng/mL developed liver dysfunction with coagulation disorders requiring multiple transfusions of fresh frozen plasma (FFP), Octaplex® and cryoprecipitate, and hypoalbuminemia treated with numerous albumin infusions. Furthermore, severe cholestasis was observed with direct bilirubin levels up to 33.14 mg/dL. Additionally, the child developed transient myelosuppression with neutropenia, thrombocytopenia, and low reticulocyte count due to several blood transfusions. The differential diagnosis tests were conducted to rule out any causes of hepatic failure other than hemolytic disease of the newborn. This case proves that adequate treatment of severe HDFN with anemia requiring IUT and hepatic failure can lead to positive outcomes with no long-term consequences.

Identification and management of fetal anemia due to hemolytic disease

INTRODUCTION

Hemolytic disease of the fetus and newborn (HDFN) is a condition caused by maternal alloantibodies against fetal red blood cells (RBCs) that can cause severe morbidity and mortality in the fetus and newborn. Adequate screening programs allow for timely prevention and intervention resulting in significant reduction of the disease over the last decades. Nevertheless, HDFN still occurs and with current treatment having reached an optimum, focus shifts toward noninvasive therapy options.

AREAS COVERED

This review focusses on the timely identification of high risk cases and antenatal management. Furthermore, we elaborate on future perspectives including improvement of screening, identification of high risk cases and promising treatment options.

EXPERT OPINION

In high-income countries mortality and morbidity rates due to HDFN have drastically been reduced over the last decades, yet worldwide anti-D mediated HDFN still accounts for 160,000 perinatal deaths and 100,000 patients with disabilities every year. Much of these deaths and disabilities could have been avoided with proper identification and prophylaxis. By implementing sustainable prevention, screening, and disease treatment measures in all countries this will systemically reduce unnecessary perinatal deaths. There is a common responsibility to engage in this cause.

Maternal bleeding complications in pregnancies affected by red blood cell alloimmunization

OBJECTIVE

To investigate whether women with red blood cell (RBC)¹ alloimmunization are more likely to experience bleeding complications during pregnancy or delivery than women without RBC alloimmunization.

STUDY DESIGN

Retrospective study involving all singleton pregnancies affected by RBC alloimmunization and without pre-existing maternal bleeding disorders or placenta previa, from 1 July 1999 to 30 June 2019 ("cases"). Only bleedings not related to invasive procedures (amnio- or cordocenteses) were included. Patients who were already at increased risk of pre- or perinatal bleeding due to their medical history (pre-existing bleeding disorders, antithrombotic therapy), or known obstetrics parameters (placental abnormalities etc.) were not included a priori. Cases were compared to controls without RBC alloimmunization, matched for maternal age and body mass index, from the same tertiary referral center in Austria.

RESULTS

130 cases were compared to 130 controls. Cases had significantly more previous pregnancies and miscarriages and their newborns had lower birthweight and were more often transferred to the intensive care unit than newborns of controls. 18/130 (13.8%) cases, compared to 8/130 (6.2%) controls experienced any bleeding during pregnancy or delivery (p = 0.061). Bleeding most often happened during the third trimester (cases: 4.6% vs. controls 0.8%, p = 0.12) and during or after delivery (cases: 7.7% vs. controls: 4.6%, p = 0.168). Binary logistic regression for the prediction of any bleeding complication during pregnancy, delivery or postpartum revealed immunization against RBC antigens as the only independent contributor (p = 0.04). Age, smoking, or previous obstetric history had no influence on the likelihood of maternal bleeding complications. Neither RBC antibody specificity nor titers were predictive of maternal bleeding during pregnancy or delivery.

CONCLUSION

Pregnancies affected by RBC alloimmunization might be at increased risk of maternal bleeding complications during pregnancy and delivery.

Identification and management of congenital parvovirus B19 infection

Parvovirus B19 (B19V) infection is well known for its mild, self-limiting clinical presentations in children, such as erythema infectiosum. Approximately 40% of women of childbearing age are susceptible to B19V infection. While maternal B19V infection usually has a good prognosis, B19V can cause severe fetal anaemia and pregnancy loss due to its ability to suppress erythroid progenitor cells. Non-invasive ultrasound monitoring for fetal anaemia is usually performed if maternal seroconversion occurs in the first 20 weeks of gestation, with amniocentesis for fetal infection reserved for those who first present with fetal anaemia or hydrops of unknown cause. Intrauterine transfusion is the standard treatment for severe fetal anaemia and is associated with a significant improvement in survival. However, survivors of hydrops fetalis may have a higher rate of long-term neurodevelopmental complications compared with non-hydropic survivors. This review aims to synthesise published data on the diagnosis, surveillance and outcomes of congenital parvovirus infection to assist clinicians in diagnosing and managing this important condition.

The rhesus incompatible pregnancy and its consequences for affected fetuses and neonates

Rhesus incompatibility in pregnancy may result in haemolytic disease of the fetus and newborn (HDFN). This review discusses the fetal, neonatal and long-term consequences of HDFN and its management. Untreated, the fetal and neonatal prognosis of HDFN is poor. Provision of intravascular intrauterine transfusion (IUT) in a dedicated referral centre significantly reduces perinatal loss. Early-onset, severe fetal anaemia carries a greater risk of adverse fetal and neonatal outcomes and is less amenable to treatment with IUT. Interventions to prevent and treat severe, early onset disease have been investigated, however evidence from randomised controlled trials is required. Neonatal consequences of Rhesus haemolytic disease include early and late postnatal anaemia, and hyperbilirubinaemia leading to bilirubin-induced neurological dysfunction. Neurodevelopmental impairment and adult cardiovascular disease are long-term complications that have been reported in association with severe fetal anaemia. Strategies to prevent fetal hydrops, and further research into the long-term impacts of fetal anaemia may improve health outcomes for adult survivors of HDFN.

Medical therapy to attenuate fetal anaemia in severe maternal red cell alloimmunisation

Haemolytic disease of the fetus and newborn (HDFN) remains an important cause of fetal mortality with potential neonatal and longer-term morbidity. HDFN is caused by maternal red cell alloimmunisation, with IgG antibodies crossing the placenta to destroy fetal erythroid cells expressing the involved antigen. Intrauterine fetal blood transfusion is the therapy of choice for severe fetal anaemia. Despite a strong evidence base and technical advances, invasive fetal therapy carries risk of miscarriage and preterm birth. Procedure-related risks are increased when invasive, in utero transfusion is instituted prior to 22 weeks to treat severe early-onset fetal anaemia. This review focuses upon this cohort of HDFN and discusses intravenous immunoglobin (IVIg) and novel monoclonal antibody (M281, nipocalimab) treatments which, if started at the end of the first trimester, may attenuate the transplacental passage and fetal effects of IgG antibodies. Such therapy has the ability to improve fetal survival in this severe presentation of HDFN when early in utero transfusion may be required and may have wider implications for the perinatal management in general.