Anti-D administration in pregnancy for preventing Rhesus alloimmunisation

Complement C3 and marginal zone B cells promote IgG-mediated enhancement of RBC alloimmunization in mice

Administration of anti-RhD immunoglobulin (Ig) to decrease maternal alloimmunization (antibody-mediated immune suppression [AMIS]) was a landmark clinical development. However, IgG has potent immune-stimulatory effects in other settings (antibody-mediated immune enhancement [AMIE]). The dominant thinking has been that IgG causes AMIS for antigens on RBCs but AMIE for soluble antigens. However, we have recently reported that IgG against RBC antigens can cause either AMIS or AMIE as a function of an IgG subclass. Recent advances in mechanistic understanding have demonstrated that RBC alloimmunization requires the IFN-α/-β receptor (IFNAR) and is inhibited by the complement C3 protein. Here, we demonstrate the opposite for AMIE of an RBC alloantigen (IFNAR is not required and C3 enhances). RBC clearance, C3 deposition, and antigen modulation all preceded AMIE, and both CD4+ T cells and marginal zone B cells were required. We detected no significant increase in antigen-specific germinal center B cells, consistent with other studies of RBC alloimmunization that show extrafollicular-like responses. To the best of our knowledge, these findings provide the first evidence of an RBC alloimmunization pathway which is IFNAR independent and C3 dependent, thus further advancing our understanding of RBCs as an immunogen and AMIE as a phenomenon.

Misclassification of RhD variants among pregnant women: a systematic review

The D antigen of the Rh blood group is considered clinically significant due to its ability to cause hemolytic transfusion reactions and hemolytic disease in the fetus and newborn. This systematic review discusses the prevalence of RhD variants among pregnant women and the importance of including RhD genotyping for prenatal testing to detect RhD variants and prevent anti-D alloimmunization. A comprehensive literature search was conducted using scientific search engines, including PubMed and MEDLINE databases, with the keywords 'anti-D alloimmunization', 'RhD variant', and 'pregnant women.' The review adhered to the PRISMA guidelines. Meta-analysis was performed using MedCalc version 20. A significance level of p≤0.05 was considered statistically significant for all two-tailed tests. The meta-analysis included four articles that met the inclusion criteria. The total prevalence of RhD positivity (RhD+) was 61% (95% CI:34%-85%). The prevalence ranged from 22% to 82%, indicating a high degree of heterogeneity between studies (I2=98.71%, p<0.0001). The overall prevalence of D variants was 15% (95% CI, 9%-23%) with a prevalence of 0.05% to 100%, showing a high degree of heterogeneity between studies (I2=99.89%, p<0.0001). Anti-D alloimmunization could occur in pregnant women with some types of RhD variants. All four studies focused on molecular testing of samples showing inconsistent or weak results with at least two anti-D antibodies using serological methods.

Society of Family Planning committee consensus on Rh testing in early pregnancy

Historical evidence that fetal red blood cell (RBC) exposure during early spontaneous or induced abortion can cause maternal Rh sensitization is limited. A close reading of these studies indicates that forgoing Rh immunoglobulin administration before 12-weeks gestation is highly unlikely to increase risk of Rh (D) antibody development, and recent studies indicate that fetal RBC exposure during aspiration abortion <12 weeks gestation is below the calculated threshold to cause maternal Rh sensitization, and the amount of fetomaternal hemorrhage during dilation and evacuation procedures up to 18-weeks gestation is adequately treated with 100-mcg of Rh immunoglobulin. We provide updated recommendations for Rh immunoglobulin administration based on this new evidence.

FIGO/ICM guidelines for preventing Rhesus disease: A call to action

The introduction of anti‐Rh(D) immunoglobulin more than 50 years ago has resulted in only a 50% decrease in Rhesus disease globally owing to a low uptake of this prophylactic approach. The International Federation of Gynecology and Obstetrics, International Confederation of Midwives, and Worldwide Initiative for Rhesus Disease Eradication have reviewed current evidence regarding the utility of anti‐Rh(D) immunoglobulin. Taking into account the effectiveness anti‐Rh(D), the new guidelines propose adjusting the dose for different indications and prioritizing its administration by indication.

These FIGO/ICM guidelines review the evidence regarding the usefulness of anti‐Rh(D) immunoglobulin, prioritizing its administration by indication.

Antenatal interventions for preventing stillbirth, fetal loss and perinatal death: an overview of Cochrane systematic reviews

BACKGROUND

Stillbirth is generally defined as a death prior to birth at or after 22 weeks' gestation. It remains a major public health concern globally. Antenatal interventions may reduce stillbirths and improve maternal and neonatal outcomes in settings with high rates of stillbirth. There are several key antenatal strategies that aim to prevent stillbirth including nutrition, and prevention and management of infections.

OBJECTIVES

To summarise the evidence from Cochrane systematic reviews on the effects of antenatal interventions for preventing stillbirth for low risk or unselected populations of women.

METHODS

We collaborated with Cochrane Pregnancy and Childbirth's Information Specialist to identify all their published reviews that specified or reported stillbirth; and we searched the Cochrane Database of Systematic Reviews (search date: 29 Feburary 2020) to identify reviews published within other Cochrane groups. The primary outcome measure was stillbirth but in the absence of stillbirth data, we used perinatal mortality (both stillbirth and death in the first week of life), fetal loss or fetal death as outcomes. Two review authors independently evaluated reviews for inclusion, extracted data and assessed quality of evidence using AMSTAR (A Measurement Tool to Assess Reviews) and GRADE tools. We assigned interventions to categories with graphic icons to classify the effectiveness of interventions as: clear evidence of benefit or harm; clear evidence of no effect or equivalence; possible benefit or harm; or unknown benefit or harm or no effect or equivalence.

MAIN RESULTS

We identified 43 Cochrane Reviews that included interventions in pregnant women with the potential for preventing stillbirth; all of the included reviews reported our primary outcome 'stillbirth' or in the absence of stillbirth, 'perinatal death' or 'fetal loss/fetal death'. AMSTAR quality was high in 40 reviews with scores ranging from 8 to 11 and moderate in three reviews with a score of 7. Nutrition interventions Clear evidence of benefit: balanced energy/protein supplementation versus no supplementation suggests a probable reduction in stillbirth (risk ratio (RR) 0.60, 95% confidence interval (CI) 0.39 to 0.94, 5 randomised controlled trials (RCTs), 3408 women; moderate-certainty evidence). Clear evidence of no effect or equivalence for stillbirth or perinatal death: vitamin A alone versus placebo or no treatment; and multiple micronutrients with iron and folic acid versus iron with or without folic acid. Unknown benefit or harm or no effect or equivalence: for all other nutrition interventions examined the effects were uncertain. Prevention and management of infections Possible benefit for fetal loss or death: insecticide-treated anti-malarial nets versus no nets (RR 0.67, 95% CI 0.47 to 0.97, 4 RCTs; low-certainty). Unknown evidence of no effect or equivalence: drugs for preventing malaria (stillbirth RR 1.02, 95% CI 0.76 to 1.36, 5 RCTs, 7130 women, moderate certainty in women of all parity; perinatal death RR 1.24, 95% CI 0.94 to 1.63, 4 RCTs, 5216 women, moderate-certainty in women of all parity). Prevention, detection and management of other morbidities Clear evidence of benefit: the following interventions suggest a reduction: midwife-led models of care in settings where the midwife is the primary healthcare provider particularly for low-risk pregnant women (overall fetal loss/neonatal death reduction RR 0.84, 95% CI 0.71 to 0.99, 13 RCTs, 17,561 women; high-certainty), training versus not training traditional birth attendants in rural populations of low- and middle-income countries (stillbirth reduction odds ratio (OR) 0.69, 95% CI 0.57 to 0.83, 1 RCT, 18,699 women, moderate-certainty; perinatal death reduction OR 0.70, 95% CI 0.59 to 0.83, 1 RCT, 18,699 women, moderate-certainty). Clear evidence of harm: a reduced number of antenatal care visits probably results in an increase in perinatal death (RR 1.14 95% CI 1.00 to 1.31, 5 RCTs, 56,431 women; moderate-certainty evidence). Clear evidence of no effect or equivalence: there was evidence of no effect in the risk of stillbirth/fetal loss or perinatal death for the following interventions and comparisons: psychosocial interventions; and providing case notes to women. Possible benefit: community-based intervention packages (including community support groups/women's groups, community mobilisation and home visitation, or training traditional birth attendants who made home visits) may result in a reduction of stillbirth (RR 0.81, 95% CI 0.73 to 0.91, 15 RCTs, 201,181 women; low-certainty) and perinatal death (RR 0.78, 95% CI 0.70 to 0.86, 17 RCTs, 282,327 women; low-certainty). Unknown benefit or harm or no effect or equivalence: the effects were uncertain for other interventions examined. Screening and management of fetal growth and well-being Clear evidence of benefit: computerised antenatal cardiotocography for assessing infant's well-being in utero compared with traditional antenatal cardiotocography (perinatal mortality reduction RR 0.20, 95% CI 0.04 to 0.88, 2 RCTs, 469 women; moderate-certainty). Unknown benefit or harm or no effect or equivalence: the effects were uncertain for other interventions examined.

AUTHORS' CONCLUSIONS

While most interventions were unable to demonstrate a clear effect in reducing stillbirth or perinatal death, several interventions suggested a clear benefit, such as balanced energy/protein supplements, midwife-led models of care, training versus not training traditional birth attendants, and antenatal cardiotocography. Possible benefits were also observed for insecticide-treated anti-malarial nets and community-based intervention packages, whereas a reduced number of antenatal care visits were shown to be harmful. However, there was variation in the effectiveness of interventions across different settings, indicating the need to carefully understand the context in which these interventions were tested. Further high-quality RCTs are needed to evaluate the effects of antenatal preventive interventions and which approaches are most effective to reduce the risk of stillbirth. Stillbirth (or fetal death), perinatal and neonatal death need to be reported separately in future RCTs of antenatal interventions to allow assessment of different interventions on these rare but important outcomes and they need to clearly define the target populations of women where the intervention is most likely to be of benefit. As the high burden of stillbirths occurs in low- and middle-income countries, further high-quality trials need to be conducted in these settings as a priority.

Antenatal and postpartum prevention of Rh alloimmunization: A systematic review and GRADE analysis

BACKGROUND

Existing systematic reviews of Rh immunoprophylaxis include only data from randomized controlled trials, have dated searches, and some do not report on all domains of risk of bias or evaluate the certainty of the evidence. Our objective was to perform an updated review, by including new trials, any comparative observational studies, and assessing the certainty of the evidence using the GRADE framework.

METHODS

We searched MEDLINE, Embase and the Cochrane Library from 2000 to November 26, 2019. Relevant websites and bibliographies of systematic reviews and guidelines were searched for studies published before 2000. Outcomes of interest were sensitization and adverse events. Risk of bias was evaluated with the Cochrane tool and ROBINS-I. The certainty of the evidence was performed using the GRADE framework.

RESULTS

Thirteen randomized trials and eight comparative cohort studies were identified, evaluating 12 comparisons. Although there is some evidence of beneficial treatment effects (e.g., at 6-months postpartum, fewer women who received RhIg at delivery compared to no RhIg became sensitized [70 fewer sensitized women per 1,000 (95%CI: 67 to 71 fewer); I2 = 73%]), due to very low certainty of the evidence, the magnitude of the treatment effect may be overestimated. The certainty of the evidence was very low for most outcomes often due to high risk of bias (e.g., randomization method, allocation concealment, selective reporting) and imprecision (i.e., few events and small sample sizes). There is limited evidence on prophylaxis for invasive fetal procedures (e.g. amniocentesis) in the comparative literature, and few studies reported adverse events.

CONCLUSION

Serious risk of bias and low to very low certainty of the evidence is found in existing RCTs and comparative observational studies addressing optimal effectiveness of Rh immunoprophylaxis. Guideline development committees should exercise caution when assessing the strength of the recommendations that inform and influence clinical practice in this area.

Recombinant anti-D for prevention of maternal-foetal Rh(D) alloimmunization: a randomized multi-centre clinical trial

Objective

To compare the efficacy and safety of recombinant anti-D (R-anti-D) with conventional polyclonal anti-D (Poly anti-D) in preventing maternal-fetal rhesus D (RhD) alloimmunization and to investigate the immunogenicity of R-anti-D.

Methods

This was a randomized, open-label, multi-center clinical trial conducted in RhD-negative pregnant women who did not receive antenatal anti-D who delivered RhD-positive babies and showed negative indirect Coombs tests (ICTs) at baseline. The women were randomized in a 2:1 ratio to R-anti-D or Poly anti-D groups and were administered 300 mcg (IM) of the corresponding drug within 72 hours of delivery. ICT was performed 72 hours, 90 days, and 180 days after anti-D injection. Serum samples were collected to check for the development of antibodies against R-anti-D at days 90 and 180, using bridging enzyme-linked immunosorbent assay. The proportion of subjects who had positive ICT results at days 90 and 180 were compared between the groups using Fisher's exact test.

Results

A total of 144 women were randomized to the R-anti-D group and 71 to the Poly anti-D group. Three women in the R-anti-D and none in the Poly anti-D group had a positive ICT result at day 90. No woman in either group had positive ICT result at day 180. Both drugs were well tolerated with only 4 reports of adverse events in each group—all were mild, non-serious, and resolved without sequelae. No subject developed antibodies against R-anti-D.

Conclusion

The studied R-anti-D is comparable in efficacy to conventional Poly anti-D and is safe and non-immunogenic.

Targeted antenatal anti-D prophylaxis for RhD-negative pregnant women: a systematic review

Background

All non-sensitized Rhesus D (RhD)-negative pregnant women in Germany receive antenatal anti-D prophylaxis without knowledge of fetal RhD status. Non-invasive prenatal testing (NIPT) of cell-free fetal DNA in maternal plasma could avoid unnecessary anti-D administration. In this paper, we systematically reviewed the evidence on the benefit of NIPT for fetal RhD status in RhD-negative pregnant women.

Methods

We systematically searched several bibliographic databases, trial registries, and other sources (up to October 2019) for controlled intervention studies investigating NIPT for fetal RhD versus conventional anti-D prophylaxis. The focus was on the impact on fetal and maternal morbidity. We primarily considered direct evidence (from randomized controlled trials) or if unavailable, linked evidence (from diagnostic accuracy studies and from controlled intervention studies investigating the administration or withholding of anti-D prophylaxis). The results of diagnostic accuracy studies were pooled in bivariate meta-analyses.

Results

Neither direct evidence nor sufficient data for linked evidence were identified. Meta-analysis of data from about 60,000 participants showed high sensitivity (99.9%; 95% CI [99.5%; 100%] and specificity (99.2%; 95% CI [98.5%; 99.5%]).

Conclusions

NIPT for fetal RhD status is equivalent to conventional serologic testing using the newborn’s blood. Studies investigating patient-relevant outcomes are still lacking.

A Multicenter, Randomized, Open-Label Trial Comparing the Efficacy and Safety of Monoclonal Anti-Rh (D) Immunoglobulin with Polyclonal Anti-Rh (D) Immunoglobulin for the Prevention of Maternal Rh-Isoimmunization

Objectives

To compare the efficacy and safety of monoclonal anti-Rhesus (anti-D) immunoglobulin (IgG) with polyclonal anti-D IgG in the prevention of maternal Rh-isoimmunization.

Methods

This was a randomized, multicenter, open-label, comparative clinical trial conducted in the obstetric in-patient departments of nine tertiary care hospitals in India. 206 Rhesus (D)-negative women, not sensitized to Rh antigen, and delivering Rh positive babies, received postpartum intramuscular administration of monoclonal or polyclonal anti-D IgG. The main outcome measures were the proportion of subjects protected from Rh-isoimmunization, identified by a negative indirect Coombs test (ICT) result, at day 180 after anti-D IgG administration, and incidence of adverse events.

Results

105 subjects were randomized to the monoclonal group and 101 to the polyclonal group. 94 from the monoclonal group had a negative ICT result and none had a positive ICT result at day 180, whereas 87 from the polyclonal group had a negative ICT result and one had a positive ICT result; the rest (11 and 13 subjects respectively) were lost to follow-up. A total of 5 adverse events were reported (3 in the monoclonal group and 2 in the polyclonal group); only one of these was serious. All the adverse events were judged to be unrelated to the interventional drug. None of the subjects in the monoclonal group developed immunogenic reaction to the monoclonal anti-D.

Conclusion

The efficacy and safety of the monoclonal preparation of anti-D was comparable to the polyclonal preparation of anti-D when used in the prevention of maternal Rh-isoimmunization.Trial registration Clinical Trial Registration Number: CTRI/2015/09/006172.

Efficacy of Antenatal Intravenous Immunoglobulin Treatment in Pregnancies at High Risk due to Alloimmunization to Red Blood Cells

Background

Alloimmunization to red blood cells (RBCs) may result in fetal anemia prior to 20 weeks gestation. The question as to whether early commencement of antenatal treatment with high-dose intravenous immunoglobulins (IVIG) may prevent or at least delay the development of fetal anemia in the presence of alloantibodies to RBCs is highly relevant.

Patients and Results

Here we describe a patient with high-titer anti-K and two other severely affected pregnant women with a history of recurrent pregnancy loss due to high-titer anti-D or anti-D plus anti-C. Early commencement of treatment with IVIG (1 g/kg/week) resulted in prevention of intrauterine transfusion (IUT) in the former two cases, and in a significant delay of development of fetal anemia in the remaining case (26 weeks gestation).

Conclusion

Based on our findings and of previously published cases, early initiation of treatment of severely alloimmunized women with IVIG (1 g/kg/week) could potentially improve the outcome of fetuses at risk.

Red Blood Cell Alloimmunization in the Pregnant Patient

Alloimmunization to red blood cell (RBC) antigens represents a challenge for physicians caring for women of child bearing potential. Exposure to non-self RBC antigens may occur during transfusion or pregnancy leading to the development of antibodies. If a subsequent fetus bears that antigen, maternal antibodies may attack the fetal red blood cells causing red cell destruction and clinically significant hemolytic disease of the fetus and newborn (HDFN). In the most severe cases, HDFN may result in intrauterine fetal demise due to high output cardiac failure, effusions and ascites, known as "hydrops fetalis". This article reviews strategies for management and prevention of RBC alloimmunization in women of child bearing potential.

Modelling stillbirth mortality reduction with the Lives Saved Tool

BACKGROUND

The worldwide burden of stillbirths is large, with an estimated 2.6 million babies stillborn in 2015 including 1.3 million dying during labour. The Every Newborn Action Plan set a stillbirth target of ≤12 per 1000 in all countries by 2030. Planning tools will be essential as countries set policy and plan investment to scale up interventions to meet this target. This paper summarises the approach taken for modelling the impact of scaling-up health interventions on stillbirths in the Lives Saved tool (LiST), and potential future refinements.

METHODS

The specific application to stillbirths of the general method for modelling the impact of interventions in LiST is described. The evidence for the effectiveness of potential interventions to reduce stillbirths are reviewed and the assumptions of the affected fraction of stillbirths who could potentially benefit from these interventions are presented. The current assumptions and their effects on stillbirth reduction are described and potential future improvements discussed.

RESULTS

High quality evidence are not available for all parameters in the LiST stillbirth model. Cause-specific mortality data is not available for stillbirths, therefore stillbirths are modelled in LiST using an attributable fraction approach by timing of stillbirths (antepartum/ intrapartum). Of 35 potential interventions to reduce stillbirths identified, eight interventions are currently modelled in LiST. These include childbirth care, induction for prolonged pregnancy, multiple micronutrient and balanced energy supplementation, malaria prevention and detection and management of hypertensive disorders of pregnancy, diabetes and syphilis. For three of the interventions, childbirth care, detection and management of hypertensive disorders of pregnancy, and diabetes the estimate of effectiveness is based on expert opinion through a Delphi process. Only for malaria is coverage information available, with coverage estimated using expert opinion for all other interventions. Going forward, potential improvements identified include improving of effectiveness and coverage estimates for included interventions and addition of further interventions.

CONCLUSIONS

Known effective interventions have the potential to reduce stillbirths and can be modelled using the LiST tool. Data for stillbirths are improving. Going forward the LiST tool should seek, where possible, to incorporate these improving data, and to continually be refined to provide an increasingly reliable tool for policy and programming purposes.