Underreporting of mortality from RhD haemolytic disease in Scotland and its implications: retrospective review

Urgent global opportunities to prevent birth defects

Birth defects are an urgent global health priority. They affect millions of births worldwide. But their prevalence and impact are largely under-ascertained, particularly in middle- and low-income countries. Fortunately, a large proportion of birth defects can be prevented. This review examines the global prevalence and primary prevention methods for major preventable birth defects: congenital rubella syndrome, folic acid-preventable spina bifida and anencephaly, fetal alcohol syndrome, Down syndrome, rhesus hemolytic disease of the fetus and the newborn; and those associated with maternal diabetes, and maternal exposure to valproic acid or iodine deficiency during pregnancy. Challenges to prevention efforts are reviewed. The aim of this review is to bring to the forefront the urgency of birth defects prevention, surveillance, and prenatal screening and counseling; and to help public health practitioners develop population-based birth defects surveillance and prevention programs, and policy-makers to develop and implement science-based public health policies.

Human platelet antigen (HPA)-1a peptides do not reliably suppress anti-HPA-1a responses using a humanized severe combined immunodeficiency (SCID) mouse model

Fetal and neonatal alloimmune thrombocytopenia (FNAIT) occurs most frequently when human platelet antigen (HPA)-1a-positive fetal platelets are destroyed by maternal HPA-1a immunoglobulin (Ig)G antibodies. Pregnancies at risk are treated by administration of high-dose intravenous Ig (IVIG) to women, but this is expensive and often not well tolerated. Peptide immunotherapy may be effective for ameliorating some allergic and autoimmune diseases. The HPA-1a/1b polymorphism is Leu/Pro33 on β3 integrin (CD61), and the anti-HPA-1a response is restricted to HPA-1b1b and HLA-DRB3*0101-positive pregnant women with an HPA-1a-positive fetus. We investigated whether or not HPA-1a antigen-specific peptides that formed the T cell epitope could reduce IgG anti-HPA-1a responses, using a mouse model we had developed previously. Peripheral blood mononuclear cells (PBMC) in blood donations from HPA-1a-immunized women were injected intraperitoneally (i.p.) into severe combined immunodeficient (SCID) mice with peptides and HPA-1a-positive platelets. Human anti-HPA-1a in murine plasma was quantitated at intervals up to 15 weeks. HPA-1a-specific T cells in PBMC were identified by proliferation assays. Using PBMC of three donors who had little T cell reactivity to HPA-1a peptides in vitro, stimulation of anti-HPA-1a responses by these peptides occurred in vivo. However, with a second donation from one of these women which, uniquely, had high HPA-1a-specific T cell proliferation in vitro, marked suppression of the anti-HPA-1a response by HPA-1a peptides occurred in vivo. HPA-1a peptide immunotherapy in this model depended upon reactivation of HPA-1a T cell responses in the donor. For FNAIT, we suggest that administration of antigen-specific peptides to pregnant women might cause either enhancement or reduction of pathogenic antibodies.

Serologic and molecular investigations of DAR1 (weak D Type 4.2), DAR1.2, DAR1.3, DAR2 (DARE), and DARA

BACKGROUND

The partial D variant DAR1 (weak D Type 4.2) is caused by three single-point mutations, 602C>G, 667T>G, and 1025T>C. Here we report a molecular study on different D variants belonging to the DAR category (DAR1, DAR1.2, DAR1.3, and DAR2) and their serologic data.

STUDY DESIGN AND METHODS

A total of 42 samples belonging to the DAR category were screened for the presence of the silent mutations 744C>T and 957G>A. The samples were phenotyped for RhD and RhCE, characterized for RhD epitope expression, and sequenced for RHD exons. Flow cytometry was performed to determine RhD antigen density.

RESULTS

The silent mutation 744C>T was found in all six samples previously typed as RHD*DAR2 (602C>G, 667T>G, 957G>A, 1025T>C). In addition to the three nucleotide changes originally reported for the RHD*DAR1 allele, the silent mutations 744C>T and 957G>A were found in 14 of 16 samples previously typed as RHD*DAR1. In the remaining two samples one additional silent mutation, 744C>T, was found. Serologically the DAR1.2 and DAR1.3 samples analyzed in this study showed no distinct difference in their anti-D reaction pattern compared to each other. The anti-D reaction pattern of DARA/DAR2 showed some distinct differences compared to those of DAR1.2 and DAR1.3.

CONCLUSION

RHD*DARA and RHD*DAR2 are the same allele. Furthermore, the alleles RHD*DAR1.2 and RHD*DAR1.3 both exist; however, the silent mutation 957G>A (V319) showed no influence on the RhD phenotype.

Routine antenatal anti-D prophylaxis in women who are Rh(D) negative: meta-analyses adjusted for differences in study design and quality

BACKGROUND

To estimate the effectiveness of routine antenatal anti-D prophylaxis for preventing sensitisation in pregnant Rhesus negative women, and to explore whether this depends on the treatment regimen adopted.

METHODS

Ten studies identified in a previous systematic literature search were included. Potential sources of bias were systematically identified using bias checklists, and their impact and uncertainty were quantified using expert opinion. Study results were adjusted for biases and combined, first in a random-effects meta-analysis and then in a random-effects meta-regression analysis.

RESULTS

In a conventional meta-analysis, the pooled odds ratio for sensitisation was estimated as 0.25 (95% CI 0.18, 0.36), comparing routine antenatal anti-D prophylaxis to control, with some heterogeneity (I²  =  19%). However, this naïve analysis ignores substantial differences in study quality and design. After adjusting for these, the pooled odds ratio for sensitisation was estimated as 0.31 (95% CI 0.17, 0.56), with no evidence of heterogeneity (I²  =  0%). A meta-regression analysis was performed, which used the data available from the ten anti-D prophylaxis studies to inform us about the relative effectiveness of three licensed treatments. This gave an 83% probability that a dose of 1250 IU at 28 and 34 weeks is most effective and a 76% probability that a single dose of 1500 IU at 28-30 weeks is least effective.

CONCLUSION

There is strong evidence for the effectiveness of routine antenatal anti-D prophylaxis for prevention of sensitisation, in support of the policy of offering routine prophylaxis to all non-sensitised pregnant Rhesus negative women. All three licensed dose regimens are expected to be effective.

Six years' experience performing RHD genotyping to confirm D- red blood cell units in Germany for preventing anti-D immunizations

BACKGROUND

Red blood cell (RBC) units of D+ donors are falsely labeled D- if regular serologic typing fails to detect low D antigen expression or chimerism. The limitations of serology can be overcome by molecular typing.

STUDY DESIGN AND METHODS

In January 2002, we introduced a polymerase chain reaction (PCR)-based assay for RHD as a routine test for first-time donors who typed D- by serologic methods including the indirect antiglobulin test. Samples were tested in pools of 20 for the RHD-specific polymorphism in Intron 4. RHD alleles were identified by PCR and nucleotide sequencing.

RESULTS

Within 6 years, 46,133 serologically D- first-time donors were screened for the RHD gene. The prevalence of RHD gene carriers detected by this method was 0.21 percent. Twenty-three RHD alleles were found of which 15 were new. Approximately one-half of the RHD gene carriers harbored alleles expressing a DEL phenotype resulting in a prevalence of 0.1 percent.

CONCLUSION

The integration of RHD genotyping into the routine screening program was practical. We report 6 years' experience of this donor testing policy, which is not performed in most transfusion services worldwide. RBC units of donors with DEL phenotype have been reported to anti-D immunize D- recipients. We transferred those donors to the D+ donor pool with the rationale of preventing anti-D immunizations, especially dreaded in pregnancies. For each population, it will be necessary to adapt the RHD genotyping strategy to the spectrum of prevalent alleles.

Ultrastructural localization of glycoprotein IIIa (GPIIIa, beta 3 integrin) on placental syncytiotrophoblast microvilli: implications for platelet alloimmunization during pregnancy

BACKGROUND

Fetal and neonatal alloimmune thrombocytopenia due to anti-human platelet antigen (HPA)-1a more commonly occurs in first pregnancies, unlike hemolytic disease of the newborn. Anti-D is produced after D+ fetomaternal hemorrhage; this usually occurs at parturition. Anti-HPA-1a could develop during pregnancy if maternal immunization is stimulated by HPA-1a expressed not only on platelets but also on other fetal cells.

STUDY DESIGN AND METHODS

An ultrastructural study of fetal placental chorionic villi was undertaken to determine the localization of glycoprotein (GP)IIIa carrying the HPA-1a/1b polymorphism. First trimester and term villi were incubated with a monoclonal antibody (MoAb) to GPIIIa or with positive control MoAbs (anti-placental alkaline phosphatase and ED822 MoAb) to villous syncytiotrophoblast (ST). Binding of MoAbs was detected with a gold-conjugated secondary antibody before processing the tissues and examination of ultrathin sections in an electron microscope.

RESULTS

Gold particles were evident on microvilli on the apical surface of ST when labeled with anti-GPIIIa and the placenta-specific MoAbs but not with an isotype control antibody. Immunolabeling for anti-GPIIIa on first trimester ST was similar to that of term ST.

CONCLUSION

The apical surface of the ST is bathed in maternal blood. During the natural regenerative process of human placenta, senescent parts of the ST are shed into maternal blood during pregnancy. This includes both apoptotic ST nuclei and microparticulate ST debris. The presence of GPIIIa on this circulating ST cellular material could be the source of HPA-1a alloantigen causing primary immunization of susceptible primigravidae early enough for anti-HPA-1a to cause fetal thrombocytopenia during a first pregnancy.

Sistema de informações hospitalares do sistema único de saúde (SIH-SUS): uma avaliação preliminar do seu desempenho no monitoramento da doença hemolítica perinatal Rh(D)

Considerando a utilização de bases administrativas na vigilância epidemiológica, propõe-se aqui avaliar a adequação do Sistema de Informações Hospitalares do Sistema Único de Saúde (SIH-SUS) na identificação dos casos de doença hemolítica perinatal ocorridos no Instituto Fernandes Figueira, Fundação Oswaldo Cruz (IFF/FIOCRUZ), entre 1998 e 2003. Foram analisadas informações disponibilizadas pelo Serviço Neonatal, pelo Arquivo Médico e os dados da Autorização de Internação Hospitalar (AIH) consolidados no SIH-SUS. A identificação dos casos de doença hemolítica perinatal se deu através dos campos Diagnóstico Primário, Diagnóstico Secundário e Procedimento Realizado. Nesse período, 194 neonatos foram diagnosticados com doença hemolítica perinatal. No Arquivo Médico, 148 casos foram registrados, porém apenas 147 AIHs foram emitidas e 145 consolidadas no SIH-SUS. Entre essas, 84 AIHs arrolavam a doença hemolítica perinatal como Diagnóstico Primário; considerando também o Diagnóstico Secundário, mais 38 casos foram identificados; e nenhum caso adicional foi recuperado pelo Procedimento Realizado. Assim, o SIH-SUS identificou apenas 122 (62,9%) dos 194 neonatos com doença hemolítica perinatal assistidos no IFF/FIOCRUZ. Mesmo que ainda requerendo uma reavaliação em outros hospitais, a utilização do SIH-SUS no monitoramento da doença hemolítica perinatal não parece recomendável. Estudos ancilares são necessários quando do emprego de dados secundários nesse contexto.

Relationship between obstetric history and Rh(D) alloimmunization severity

BACKGROUND

To evaluate the relationship between obstetric history and Rh(D) alloimmunization severity, employing the gestational age at the first intrauterine fetal transfusion (IUT) as an indicator of this severity.

METHODS

From 1996 to 2006, Rh(D) alloimmunized pregnancies submitted to IUT had their data assessed. Gestational age at the first IUT was modeled as a linear outcome. The associations between obstetric history variables, anti-Rh(D) antibodies titer and gestational age at the first IUT were analyzed. Statistics are presented with 95% confidence intervals (P < 0.05).

RESULTS

A total of 82 non-hydropic anemic fetuses, ensuing in 92.7% (n = 76) of perinatal survival, were submitted to IUT. Nineteen (23,2%) pregnant women did not present with any previous stillbirth, neonatal death, IUT, hydrops or neonatal exchange transfusion (group 1); and 63 (76.8%) reported at least one of these events (group 2). Gestational age at the first IUT differed significantly between the groups (P = 0.0001). For group 1, it ranged from 24 to 35 weeks (median 32.5 weeks), whereas for group 2 it ranged from 19 to 34 weeks (median 27 weeks). In the multivariated analysis, previous neonatal death (P = 0.040), previous IUT (P = 0.000) and previous neonatal exchange transfusion (P = 0.036) were independently associated with the gestational age at the first IUT.

CONCLUSIONS

The evaluation of the obstetrical history is an important diagnostic tool for predicting Rh(D) alloimmunization severity. Alloimmunized pregnant women who reported previous neonatal death(s), neonatal exchange transfusion(s) or IUT(s) should receive a closer fetal surveillance due to the risk of a higher rate of fetal hemolysis and the need of an earlier IUT.

Fetal hematocrit decrease after repeated intravascular transfusions in alloimmunized pregnancies

BACKGROUND

The aim of this study is to evaluate the fetal hematocrit (Hct) decrease along repeated intravascular intrauterine fetal transfusions (IUTs) and test the hypothesis that, after consecutive IUTs, there is a lower Hct drop off.

METHODS

From July 1996 to June 2006, pregnancies submitted to IUT for fetal hemolytic anemia treatment had their data assessed. The daily rate of decrease in fetal Hct was calculated by dividing the difference between the posttransfusion Hct of the previous IUT and the pretransfusion Hct of the current IUT, by the number of days between the transfusions. Fetuses with other abnormalities or submitted to intraperitoneal transfusions were excluded.

RESULTS

Eighty-one women were submitted to IUT during the alluded period, ensuing 296 intrauterine transfusions. The perinatal survival was 89.9% (n = 80), with 92.0% (n = 69) of nonhydropic fetuses survival. Hydropic fetuses showed higher hematocrit drop off than nonhydropic ones (P < 0.01). Compared to the interval between the first and second IUT, the daily fetal Hct decline was lower after the third one (P < 0.05). Stratifying by the presence of hydrops, nonhydropic fetuses showed a smaller decrease at the third and fourth intervals (P < 0.01 and P < 0.05, respectively). Among hydropic fetuses, there is a trend of smaller Hct decrease along successive IUTs (interval 3, P = 0.08; interval 4, P = 0.07; and interval 5, P = 0.10).

CONCLUSIONS

Following some IUTs, fetal hematocrit decrease is lower and larger intervals between the transfusions could be accomplished. Multicenter studies should investigate an algorithm for timing subsequent IUTs, considering Doppler values, estimated fetal hematocrit decline and other parameters.

Unexpected rapid rise of maternal serum anti-D levels during pregnancy

Two cases are described where hydrops faetalis developed as a result of very sudden and unexpected rises in serum anti-D levels. In both cases intravascular intrauterine transfusion was employed and a favourable outcome obtained. These cases show that continued vigilance is required even when anti-D levels are low. Weak antibody titres may be detected using enzyme-treated red cells, and failure to use this more sensitive technique meant that in one of the cases the initial weak antibody was not detected. There is currently a debate about the use of this more sensitive test in view of the increased work involved.

Treatment requirements of infants with rhesus isoimmunisation within a geographically defined area

OBJECTIVE

To provide population based data on the treatment requirements of infants with rhesus isoimmunisation.

SETTING

Twenty nine hospitals in South Thames in which 81 119 deliveries occurred between February 1999 and January 2000.

DESIGN

Every month, a clinician identified in each of the hospitals sent back a postcard indicating whether or not an infant with RhD had required treatment in their institution. Antenatal and postnatal information was then requested from all those who gave positive responses.

MAIN OUTCOME MEASURES

Requirement for postnatal treatment for rhesus isoimmunisation.

RESULTS

During the one year study period, only 26 infants required treatment for rhesus isoimmunisation. The median duration of phototherapy of the 26 infants was five days (range 1-12). Seven infants required at least one exchange transfusion (two required two exchange transfusions), and seven infants received one "top up" transfusion. None received erythropoietin and no infant died.

CONCLUSION

The results suggest that few infants require treatment for rhesus isoimmunisation.

The role of immunoglobulins in neonatal Rhesus haemolytic disease

Rhesus (Rh) isoimmunisation is the most common form of severe haemolytic disease of the newborn (HDN). The introduction of prophylaxis with anti-D Rh0 immunoglobulin (anti-D) has resulted in a marked reduction in the sensitisation of Rh-negative women and deaths attributable to Rh HDN. The sensitisation rate could be further decreased if there was strict adherence to the guidelines for administration of anti-D prophylaxis. Whether additional prophylaxis at 28 and 34 weeks of gestation would be cost effective is controversial. Intrauterine transfusions to treat fetal anaemia, postnatal exchange transfusions and phototherapy are all part of the standard management of affected individuals. Intravenous immunoglobulin given to pregnant women can reduce fetal haemolysis, and when administered to neonates with Rh isoimmunisation has been associated with a reduction in the requirement for exchange transfusion. There are, however, potential risks of immunoglobulin administration, including haemolysis due to the presence of anti-A or anti-B antibodies, allergy and the transmission of disease.

Routine antenatal Rhesus D immunoglobulin prophylaxis: the results of a prospective 10 year study

OBJECTIVE

To assess the clinical and financial impact, and identify the problems, of providing routine antenatal RhD immunoglobulin prophylaxis for Rhesus D negative nulliparae.

DESIGN

A retrospective (1980-1986) and prospective (1987-1996) comparison between two similar populations, one population with nulliparae offered routine RhD immunoglobulin 500 IU prophylaxis at 28 and 34 weeks of gestation part way through the study period, and the other population not offered prophylaxis at any time.

SETTING

Obstetric units in two counties (three health districts) with similar annual numbers of maternities and the Regional Blood Transfusion Service antenatal serology laboratory.

PARTICIPANTS

Non-sensitised Rhesus D negative pregnant nulliparae.

INTERVENTIONS

Intramuscular RhD immunoglobulin 500 IU at 28 and 34 weeks of gestation to eligible women booked for confinement in one county; the intervention not offered in the other county.

MAIN OUTCOME MEASURES

1. Rhesus D sensitised second pregnancy rate; 2. success in providing prophylaxis to eligible women; 3. serology laboratory activity changes; 4. potential savings from the prophylaxis programme.

RESULTS

Prophylaxis significantly reduced iso-immunisation in the next pregnancy when compared with historical (OR 0.28, CI 0.14-0.53; P < 0.0001) and contemporary controls (OR 0.43, CI 0.22-0.86; P = 0.02). However, success at achieving comprehensive prophylaxis was disappointing, with only 89% of eligible women receiving the first injection, 74% both injections, and for only 29% were both at the correct gestation. Fifty-two percent of women delivered after 40 weeks of gestation, beyond the period of adequate prophylaxis protection. The savings in antenatal interventions, neonatal care and possible long term ill-health that result from very preterm birth should be considerable.

CONCLUSION

Routine prophylaxis for nulliparae significantly reduces the incidence of sensitised next pregnancies with consequent savings, and its adoption nationwide should be encouraged. A programme offering antenatal prophylaxis for all Rhesus D negative women is unlikely to be economic. Improvement in uptake of prophylaxis is needed; alternative administration strategies should be explored.