The contemporary management of haemolytic disease of the fetus and newborn

Haemolytic disease of the fetus and newborn (HDFN) remains an important cause of perinatal mortality and morbidity. The pathogenesis underlying this condition is maternal red cell alloimmunization, with immunoglobulin G (IgG) antibodies produced in response to 'non-self', inherited paternal antigens expressed upon fetal erythrocytes. The IgG antibodies cross the placenta into the fetal circulation causing red cell destruction and fetal anaemia. Intrauterine transfusion (IUT) remains the cornerstone therapy with fetal survival rates up to 97%, but it is an invasive, technically challenging surgical procedure performed at specialized medical centres. The procedure-related risk of IUTs is increased at gestational age before 24 weeks. This has stimulated interest in maternal medical therapies that attenuate the risk of severe fetal anaemia, increase the gestational age of first IUTs, and reduce perinatal mortality and morbidity. This review summarizes current evidence for such treatments: intravenous immunoglobulin therapy and neonatal fragment crystallizable (Fc) receptor blockade for managing severe HDFN.

The selection and preparation of red cell components for intrauterine transfusion: A national survey

BACKGROUND AND OBJECTIVES

The practice regarding the selection and preparation of red blood cells (RBCs) for intrauterine transfusion (IUT) is variable reflecting historical practice and expert opinion rather than evidence-based recommendations. The aim of this survey was to assess Canadian hospital blood bank practice with respect to red cell IUT.

MATERIALS AND METHODS

A survey was sent to nine hospital laboratories known to perform red cell IUT. Questions regarding component selection, processing, foetal pre-transfusion testing, transfusion administration, documentation and traceability were assessed.

RESULTS

The median annual number of IUTs performed in Canada was 109 (interquartile range, 103-118). RBC selection criteria included allogeneic, Cytomegalovirus seronegative, irradiated, fresh units with most sites preferentially providing HbS negative, group O, RhD negative, Kell negative and units lacking the corresponding maternal antibody without extended matching to the maternal phenotype. Red cell processing varied with respect to target haematocrit, use of saline reconstitution (n = 4), use of an automated procedure for red cell concentration (n = 1) and incorporation of a wash step (n = 2). Foetal pre-transfusion testing uniformly included haemoglobin measurement, but additional serologic testing varied. A variety of strategies were used to link the IUT event to the neonate post-delivery, including the creation of a unique foetal blood bank identifier at three sites.

CONCLUSION

This survey reviews current practice and highlights the need for standardized national guidelines regarding the selection and preparation of RBCs for IUT. This study has prompted a re-examination of priorities for RBC selection for IUT and highlighted strategies for transfusion traceability in this unique setting.

Immunohematological testing and transfusion management of the prenatal patient

The primary indication for immunohematological testing in the prenatal patient is to detect and identify maternal red cell antibodies. If there are antibodies that are expected to hemolyze the fetus' red cells, their strength of reactivity must be tested, and the fetus' antigen status determined. After delivery, testing is performed to assess the extent of fetomaternal hemorrhage, as a large hemorrhage may require other therapeutic interventions. Another major role for immunohematological testing is to select blood components appropriately when intrauterine transfusion is required for fetal anemia resulting from maternal alloimmunization or some other cause. Supplementation with molecular methods has transformed the practice of immunohematology, particularly as it applies to typing for the D antigen of the Rh blood group system. Notwithstanding the advances in testing, close coordination and communication between the transfusion service and the obstetrics service are the foundation for ensuring the finest care for prenatal patients, and for new mothers and their infants. This review describes testing and transfusion practices for prenatal patients, using case presentations to highlight the management of selected immunohematological findings. It also includes a discussion of key patient management topics that are currently unresolved.

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.

Implementation of a Standardized Prenatal Testing Protocol in an Integrated, Multihospital Health System

OBJECTIVES

When our institution grew into an integrated multihospital health system, we were faced with the need to standardize laboratory processes, including blood bank processes, across all locations. The purpose of this article is to describe our experience of standardizing the protocols for prenatal testing.

METHODS

For each hospital in the system, we established service tiers to define tests offered on site or referred to another location. For each prenatal test, we examined the related processes for ways to improve uniformity, efficiency, and reliability. Throughout this process of standardization, we collaborated with the clinical services to gain concurrence on the interpretation and reporting of results.

RESULTS

We created and implemented a uniform protocol for testing prenatal patients. The protocol standardized the definition of critical titer, instituted criteria to identify passively acquired anti-D, and established a process for the follow-up of women with inconsistent serologic results on Rh(D) typing.

CONCLUSIONS

Close collaboration with the clinical services ensured that our testing protocol is aligned with the needs of the integrated obstetrics service in the health system. The approach described in this article may provide a plan outline for pathologists facing similar challenges at other integrated health systems.

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.

Red cell alloimmunization: A 2020 update

Management of maternal red cell alloimmunization has been revolutionized over the last 60 years. Advances in the prevention, screening, diagnosis, and treatment of alloimmune-induced fetal anemia make this condition an exemplar for contemporary practice in fetal therapy. Since survival is now an expectation, attention has turned to optimization of long-term outcomes following an alloimmunized pregnancy. In this review, the current management of red cell alloimmunization is described. Current research and future directions are discussed with particular emphasis on later life outcomes after alloimmune fetal anemia.