Rh disease prevention: the European Perspective

Rhesus D Prophylaxis: When and Why We Give Rhesus D Immunoglobulin

Importance

Hemolytic disease of the fetus and newborn (HDFN) is caused by maternal alloantibodies to fetal red blood cells and is associated with significant fetal and neonatal morbidity and mortality. Rhesus D antigen (RhD)-mediated HDFN is the only preventable cause of alloimmunization in pregnancy. Widespread utilization of RhD prophylaxis reduces the risk of RhD-mediated alloimmunization from 17% to <1% in at-risk pregnancies, although RhD-mediated HDFN still occurs.

Objective

To emphasize significance of RhD prophylaxis, outline current guideline-directed indications for administration, provide clarification in areas of uncertainty regarding prophylaxis administration, and review key concepts relevant to patient education and shared decision-making.

Evidence Acquisition

PubMed and Google Scholar literature search.

Results

Data over several decades have shown implementation of prenatal and postpartum RhD prophylaxis has significantly reduced incidence and morbidity of RhD-mediated HDFN. Most international guidelines recommend routine prophylaxis of Rh-negative mothers in the second trimester and peripartum, with additional prophylaxis following certain high-risk events. Recent shortages in RhD immunoglobulin (RhDIg) and new methods to determine fetal blood type have prompted renewed debate regarding criteria for prophylaxis during the first trimester.

Conclusion

Understanding indications for administration of RhD prophylaxis is essential for preventing RhD alloimmunization. Although uncertainty remains in some clinical scenarios, prophylaxis is strongly recommended in Rh-negative mothers in the second trimester, following events high-risk for sensitization in pregnancy, and postpartum.

Relevance

In this review, the etiology of alloimmunization and indications for RhDIg prophylaxis, current society recommendations, and areas of debate are summarized and discussed.

Why do people still make anti-D over 50 years after the introduction of Rho(D) immune globulin? A Biomedical Excellence for Safer Transfusion (BEST) Collaborative study

BACKGROUND

Rho(D) immune globulin (RhIg) is used to reduce RhD alloimmunization in pregnancy. This study describes potential causes for RhD alloimmunization after the development and implementation of RhIg.

STUDY DESIGN AND METHODS

This retrospective descriptive study investigated RhD-negative patients born in 1965-2005 with anti-D newly identified during 2018-2022. Transfusion, pregnancy, intravenous drug abuse, and transplantation were considered potential alloimmunization sources.

RESULTS

There were 1200 study patients (852 females; 348 males) at 30 institutions in 5 countries (USA, Canada, UK, New Zealand, Brazil). Most patients had a single potential source of alloimmunization identified (857/1200, 71%), most commonly pregnancy among females (537/852, 63%) and transfusion among males (180/348, 52%). When multiple potential sources were included, males were more likely than females to have a history of transfusion (235/348 [68%] vs. 149/852 [17%], p < .0001) and confirmed or suspected intravenous drug abuse (100/348 [29%] vs. 138/852 [16%], p < .0001). Among females with a history of pregnancy, 119/718 (17%) had healthcare access issues, 120/718 (17%) had pregnancy in a country where they may not have received RhIg, and 21/718 (3%) refused RhIg. Among patients with a history of transfusion, males were more likely than females to have received RhD-positive red blood cells or whole blood (143/235 [61%] vs. 30/149 [20%], p < .0001) and/or platelets (84/235 [36%] vs. 19/149 [13%], p < .0001).

DISCUSSION

Pregnancy was the most frequently identified potential source of RhD alloimmunization among females. Transfusion was most frequent in males. Intravenous drug abuse as a common potential source among patients with RhD alloimmunization merits further study.

Management of anti-D prophylaxis in RhD negative women undergoing early medical abortion - an international practice survey among practitioners

AIM

We evaluated the current practices of abortion providers giving anti-D prophylaxis to RhD negative women undergoing first trimester medical abortion and factors that influenced the decision. We also examined RhD management strategies that could be safely adopted.

METHODS

A Steering Committee of abortion providers drafted a questionnaire on anti-D prophylaxis practices and perceptions. The 28-question survey, hosted online from December 2022 to December 2023, targeted international abortion providers.

RESULTS

Almost 62% of respondents perform medical abortion during the first trimester (up to 12 weeks of amenorrhoea [WA]), while 32.8% provide it during the second trimester (13 to 26 WA). Among providers, 55.8% administer anti-D prophylaxis to all RhD negative women during first trimester medical abortions, 25.5% provide it selectively, and 18.6% do not administer it at all. Providers who do not administer IgG anti-D rely on national guidelines (51.2%), hospital protocols (16.3%), or both (7.0%), citing early gestational age (36.5%) and insufficient evidence (22.9%) as reasons. The primary reason for administering IgG anti-D was preventing risks in future pregnancies (52.7%). Yet, 59.1% expressed interest in changing their anti-D prophylaxis practices during early abortion.

CONCLUSION

This study highlights the huge variations in anti-D prophylaxis practices during first trimester medical abortion. These discrepancies mirror differences in national and international guidelines and underscore the need for robust clinical evidence to determine the gestational age limits for alloimmunization risk and support protocol updates.

Evaluation of the clinical effect of a nationwide implementation of targeted routine antenatal anti-D prophylaxis in Denmark

BACKGROUND

In 2010, Denmark was the first country to implement a targeted routine antenatal anti-D prophylaxis (tRAADP) program, offering fetal RHD genotyping to all nonimmunized D negative pregnant women. The program represented a shift from only postnatal prophylaxis to a combined antenatal and postnatal prophylaxis. This study aimed to evaluate the clinical effect of tRAADP in Denmark.

STUDY DESIGN AND METHODS

This nationwide registry-based cohort study included all D negative women who gave birth between 2004-2020, identified through the National Medical Birth Register and the Departments of Clinical Immunology in Denmark. The clinical effect of tRAADP was assessed by comparing the incidence of new D immunization between 2004-2009 (non-tRAADP-cohort) and 2011-2018 (tRAADP-cohort).

RESULTS

A total of 282 women were D immunized during pregnancy between 2004-2009 (non-tRAADP-cohort), and 167 between 2011-2018 (tRAADP-cohort). The incidence of new D immunization decreased from 0.46% (95% CI 0.41-0.52) in the non-tRAADP-cohort to 0.22% (95% CI 0.19-0.25) in the tRAADP-cohort. The risk reduction was statistically significant p < 0.001. Notably, in the tRAADP cohort 0.1% (95% CI 0.08-0.12) of new D immunizations occurred before the time of antenatal prophylaxis.

DISCUSSION

tRAADP significantly reduced the incidence of new D immunization by more than half, thus demonstrating the expected effect. However, even with full adherence to the current program, some women with early fetomaternal hemorrhage (FMH) were still at risk. Future studies may evaluate the impact of administering an additional tRAADP dose earlier in the second trimester to prevent this.

Maternal red blood cell alloimmunization prevalence in the United States

ABSTRACT

Hemolytic disease of fetus and newborn (HDFN) is a life-threatening disease mediated by maternal alloimmunization to red blood cell (RBC) antigens. Studies of maternal alloimmunization prevalence in the United States lack national data. This study describes prevalence and trends in alloimmunization in pregnancy in the United States. RBC antibodies (abs) were identified in a large, nationwide, commercial laboratory database from 2010 through 2021. The cohort comprised pregnancies for which the year of laboratory collection and patient's state of residence were available. Data were normalized based on US Centers for Disease Control and Prevention estimates of live births and weighted by year and US Census Division. Cochrane-Armitage tests assessed temporal trends of alloimmunization. Of 9 876 196 pregnancies, 147 262 (1.5%) screened positive for RBC abs, corresponding to an estimated prevalence of 1518 of 100 000 pregnancies. Of identified RBC abs, anti-D comprised 64.1% pregnancies (586/100 000). Prevalence of other high-risk RBC abs for HDFN included anti-K (68/100 000) and anti-c (29/100 000). Incidence of all 3 high-risk abs increased from 2010 to 2021 (all P < .001). Among almost 10 million pregnancies in the United States, comprising an estimated 14.4% of all pregnancies, 1.5% screened positive for RBC abs. Almost three-quarters (679/100 000 [74.3%]) of RBC abs identified were high risk for HDFN. Although prevalence of anti-D is difficult to interpret without the ability to distinguish alloimmunization from passive immunity, it remains problematic in HDFN, ranking second only to anti-K in critical titers. Given the sequelae of HDFN, new initiatives are required to reduce the incidence of alloimmunization in patients of reproductive potential.

Evaluation of the LightCycler® PRO Instrument as a Platform for Rhesus D Typing

Rapid and reliable Rhesus D typing is crucial for blood donation centers. In instances of massive blood transfusion or reduced antigen expression, DNA-based phenotype prediction becomes mandatory. Our molecular RHD typing approach involves an initial real-time PCR for the most common aberrant RHD types in our region, RHD*01W.1 (weak D type 1), RHD*01W.2 (weak D type 2), RHD*01W.3 (weak D type 3), and RHD*07.01 (DVII). For comprehensive coverage, Sanger sequencing of RHD coding regions is performed in the case of PCR target-negative results. We evaluated the specificity and accuracy of these methods using the recently launched LightCycler® PRO real-time platform. All findings demonstrated remarkable accuracy. Notably, the LightCycler® PRO instrument offers a distinct advantage in data interpretation and integration via the HL7 interface. This study underlines the importance of including advanced molecular techniques in blood typing protocols, especially in scenarios where conventional serological methods may be insufficient.

Antenatal RHD screening to guide antenatal anti-D immunoprophylaxis in non-immunized D- pregnant women

In pregnancy, D- pregnant women may be at risk of becoming immunized against D when carrying a D+ fetus, which may eventually lead to hemolytic disease of the fetus and newborn. Administrating antenatal and postnatal anti-D immunoglobulin prophylaxis decreases the risk of immunization substantially. Noninvasive fetal RHD genotyping, based on testing cell-free DNA extracted from maternal plasma, offers a reliable tool to predict the fetal RhD phenotype during pregnancy. Used as a screening program, antenatal RHD screening can guide the administration of antenatal prophylaxis in non-immunized D- pregnant women so that unnecessary prophylaxis is avoided in those women who carry a D- fetus. In Europe, antenatal RHD screening programs have been running since 2009, demonstrating high test accuracies and program feasibility. In this review, an overview is provided of current state-of-the-art antenatal RHD screening, which includes discussions on the rationale for its implementation, methodology, detection strategies, and test performance. The performance of antenatal RHD screening in a routine setting is characterized by high accuracy, with a high diagnostic sensitivity of ≥99.9 percent. The result of using antenatal RHD screening is that 97-99 percent of the women who carry a D- fetus avoid unnecessary prophylaxis. As such, this activity contributes to avoiding unnecessary treatment and saves valuable anti-D immunoglobulin, which has a shortage worldwide. The main challenges for a reliable noninvasive fetal RHD genotyping assay are low cell-free DNA levels, the genetics of the Rh blood group system, and choosing an appropriate detection strategy for an admixed population. In many parts of the world, however, the main challenge is to improve the basic care for D- pregnant women.

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.

Risk factors for RhD immunisation in a high coverage prevention programme of antenatal and postnatal RhIg: a nationwide cohort study

OBJECTIVE

To evaluate which risk factors for RhD immunisation remain, despite adequate routine antenatal and postnatal RhIg prophylaxis (1000 IU RhIg) and additional administration of RhIg. The second objective was assessment of the current prevalence of RhD immunisations.

DESIGN

Prospective cohort study.

SETTING

The Netherlands.

POPULATION

Two-year nationwide cohort of alloimmunised RhD-negative women.

METHODS

RhD-negative women in their first RhD immunised pregnancy were included for risk factor analysis. We compared risk factors for RhD immunisation, occurring either in the previous non-immunised pregnancy or in the index pregnancy, with national population data derived from the Dutch perinatal registration (Perined).

RESULTS

In the 2-year cohort, data from 193 women were eligible for analysis. Significant risk factors in women previously experiencing a pregnancy of an RhD-positive child (n = 113) were: caesarean section (CS) (OR 1.7, 95% CI 1.1-2.6), perinatal death (OR 3.5, 95% CI 1.1-10.9), gestational age >42 weeks (OR 6.1, 95% CI 2.2-16.6), postnatal bleeding (>1000 ml) (OR 2.0, 95% CI 1.1-3.6), manual removal of the placenta (MRP) (OR 4.3, 95% CI 2.0-9.3); these factors often occurred in combination. The miscarriage rate was significantly higher than in the Dutch population (35% versus 12.-5%, P < 0.001).

CONCLUSION

Complicated deliveries, including cases of major bleeding and surgical interventions (CS, MRP), must be recognised as a risk factor, requiring estimation of fetomaternal haemorrhage volume and adjustment of RhIg dosing. The higher miscarriage rate suggests that existing RhIg protocols need adjustment or better compliance.

Time points and risk factors for RhD immunizations after the implementation of targeted routine antenatal anti-D prophylaxis: A retrospective nationwide cohort study

INTRODUCTION

Targeted routine antenatal anti-D prophylaxis was introduced to the national prophylaxis program in Finland in late 2013. The aim of this study was to assess the incidence, time-points, and risk factors for Rhesus D immunization after the implementation of routine antenatal anti-D prophylaxis, in all women in Finland with antenatal anti-D antibodies detected in 2014-2017.

MATERIAL AND METHODS

In a nationwide population-based retrospective cohort study, the incidence, time-points, and risk factors of anti-D immunizations were analyzed. Information on antenatal screening was obtained from the Finnish Red Cross Blood Service database, and obstetric data from hospital records and the Finnish Medical Birth Register.

RESULTS

The study included a total of 228 women (197 with complete data for all pregnancies). After the implementation of routine antenatal anti-D prophylaxis, the prevalence of pregnancies with anti-D antibodies decreased from 1.52% in 2014 to 0.88% in 2017, and the corresponding incidence of new immunizations decreased from 0.33% to 0.10%. Time-points for detection of new anti-D antibodies before and after 2014 were the first screening sample at 8-12 weeks of gestation in 52% versus 19%, the second sample at 24-26 weeks in 20% versus 50%, and the third screening at 36 weeks in 28% versus 32%.

CONCLUSIONS

The incidence of new anti-D immunizations decreased as expected after the implementation of routine antenatal anti-D prophylaxis. True failures are rare and they mainly occur when the prophylaxis is not given appropriately, suggesting a need for constant education of healthcare professionals on the subject.