Rhesus D alloimmunization in pregnancy from 1996 to 2015 in Iceland: a nation-wide population study prior to routine antenatal anti-D prophylaxis.

BACKGROUND: Rhesus D (RhD) incompatibility is still the most important cause of hemolytic disease of the fetus and newborn (HDFN) worldwide. The aim of this study was to investigate the incidence, causes, and consequences of anti-D alloimmunizations in pregnancy in Iceland, prior to implementation of targeted routine antenatal anti-D prophylaxis (RAADP) in 2018. STUDY DESIGN AND METHODS: This was a nation-wide cohort study of 130 pregnancies affected by RhD alloimmunization in Iceland in the period from 1996 through 2015. Data were collected from transfusion medicine databases, medical records, and the Icelandic Medical Birth Register. RESULTS: Of 130 RhD alloimmunizations, 80 cases (61.5%) represented new RhD immunization in the current pregnancy. Sensitization was discovered in the third trimester in 41 (51.3%) and occurred in the first pregnancy in 14 cases (17.5%). The most likely causative immunization event was the index pregnancy for 45 (56.25%), a previous pregnancy/birth for 26 (32.5%), abortion for 3 (3.75%), and unknown for 6 women (7.5%). Higher anti-D titers were associated with shorter gestational length, cesarean sections, positive direct antiglobulin test (DAT), and severe HDFN. Intrauterine transfusion (IUT) was performed in five pregnancies (3.8%), and 35 of 132 (26.5%) live-born neonates received treatment for HDFN; 32 received phototherapy (24.2%), 13 exchange transfusion (9.8%), and seven simple blood transfusion (5.3%). CONCLUSION: In about half of cases, RhD alloimmunization was caused by the index pregnancy and discovered in the third trimester. Thus, the newly implemented RAADP protocol should be effective in reducing the incidence of RhD immunization in Iceland in the future.

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.

Rh (D) alloimmunization treated by double filtration plasmapheresis.

Here in this report a 31 year old pregnant woman with positive serum antiglobulin test against anti-D antierythrocyte antibodies who was treated succesfully with double filtration plasmapheresis (DFPP) is presented. The DFPP was started in the early stage of pregnancy together with intravenous immunoglobulin therapy and the antierythrocyte antibody titer of the patient was successfully maintained in a stable level below 1:64 dilution. She delivered successfully on the 30th week of gestation. The favorable outcome of this patient implies that DFPP is an effective and safe treatment modality in pregnant women with red cell alloimmunization.

Anti-D quantification in relation to anti-D titre, middle cerebral artery Doppler measurement and clinical outcome in RhD-immunized pregnancies.

BACKGROUND: The optimal strategy to monitor RhD-immunized pregnancies is not evident. Whether a quantitative analysis of anti-D antibodies adds valuable information to anti-D titre is unclear. The aim of this study was to evaluate the relevance of anti-D quantification in routine monitoring of RhD-immunized pregnancies. MATERIALS AND METHODS: In a retrospective study, 64 consecutive pregnancies in 61 immunized women with anti-D titre ≥128 at any time during pregnancy were included. According to routine, at titre ≥128, anti-D quantification was performed by flow cytometry and the peak systolic velocity in the middle cerebral artery was measured by ultrasound. Decisions for treatment with intrauterine blood transfusion were based on increased peak systolic velocity in the middle cerebral artery. RESULTS: Increasing anti-D concentrations correlated well to increasing anti-D titres, but at each titre value, there was a large interindividual variation, in the determined anti-D concentration. Intrauterine transfusions were initiated in 35 pregnancies according to algorithms based on ultrasound measurements, at anti-D concentrations of 2·4-619 IU/ml and titre 128-16 000. Sixty pregnancies resulted in a live-born child, three in miscarriage and one in termination of pregnancy. During the perinatal care in the neonatal intensive care unit, thirty-one of the neonates were treated with blood exchange transfusions and/or red cell transfusions and 47 were treated with phototherapy. CONCLUSION: Anti-D quantification does not add further information compared to anti-D titre, in defining a critical level to start monitoring RhD-immunized pregnancies with Doppler ultrasound.

Effectiveness and costs of non-invasive foetal RHD genotyping in rhesus-D negative mothers: a French multicentric two-arm study of 850 women.

BACKGROUND: The determination of foetal Rhesus D (RHD) status allows appropriate use of IgRh prophylaxis by restricting its use to cases of RHD feto-maternal incompatibilities. There is a degree of uncertainty about the cost-effectiveness of foetal RHD determination, yet screening programs are being introduced into clinical practice in many countries. This paper evaluates the impact of non-invasive foetal Rhesus D (RHD) status determination on the costs of managing RHD-negative pregnant women and on the appropriate use of anti-D prophylaxis in a large sample of RHD-negative pregnant women using individual prospectively collected clinical and economic data. METHODS: A prospective two-armed trial of RHD negative pregnant women was performed in 11 French Obstetric Departments. Non-invasive foetal RHD genotyping was performed before 26 weeks' gestation in the experimental arm whereas the control arm participants received usual care. The costs associated with patient management in relation to their RHD negative status (biological tests, anti-D prophylaxis and visits) were calculated from inclusion to the end of the postpartum period. The costs of hospital admissions during pregnancy and delivery were also determined. RESULTS: A total of 949 patients were included by 11 centres between 2009 and 2012, and 850 completed follow-up, including medical and biological monitoring. Patients were separated into two groups: the genotyping group (n=515) and the control group (n=335). The cost of the genotyping was estimated at 140 euros per test. The total mean cost per patient was estimated at €3,259 (SD ± 1,120) and €3,004 (SD ± 1,004) in the genotyping and control groups respectively. The cost of delivery represented three quarters of the total cost in both groups. The performance of managing appropriately RHD negative anti-D prophylaxis was 88% in the genotyping group, versus 65% in the control group. Using the costs related to RHD status (biological tests, anti-D immunoglobulin injections and visits) the incremental cost-effectiveness ratio (ICER) was calculated to be €578 for each percentage gain in women receiving appropriate management. CONCLUSION: Early knowledge of the RHD status of the foetus using non-invasive foetal RHD genotyping significantly improved the management of RHD negative pregnancies with a small increase in cost. TRIAL REGISTRATION: Clinical trials registry- NCT00832962 -13 January 2009 - retrospectively registered.

Cancer type predicts alloimmunization following RhD-incompatible RBC transfusions.

BACKGROUND: Immunosuppressed, RhD-negative oncology patients tend to have lower rates of sensitization to the D antigen when they receive transfusion with RhD-positive blood components. Clinical factors associated with alloimmunization to the D antigen in RhD-negative oncology patients when they receive transfusion with RhD-positive red blood cells (RBCs) have not been well defined. STUDY DESIGN AND METHODS: This was a 4-year, retrospective analysis identifying RhD-negative oncology patients who received RhD-positive RBCs and were not previously alloimmunized to the D antigen. Age, sex, race, ABO group, primary oncology diagnosis, and numbers of RhD-incompatible RBC transfusions were recorded. The association between antibody formation and clinical factors was studied. The incidence of alloanti-D was calculated from a subsequent antibody-detection test performed at least 28 days after receipt of the first transfusion of RhD-positive RBCs. RESULTS: In total, 545 RhD-negative oncology patients received 4295 RhD-positive RBC transfusions. Of these, 76 (14%) became alloimmunized to the D antigen. Diagnosis type was the only factor significantly associated with responder status. The logistic regression model indicated that patients who had myelodysplastic syndrome or solid malignancies were more likely to be responders than those who had acute leukemia. CONCLUSION: We measured a 14% sensitization rate to the D antigen in our RhD-negative oncology population. The rate of alloimmunization was higher in patients who had solid cancers (22.6%) or myelodysplastic syndrome (23%) compared with those who had other hematologic malignancies (7%). Knowledge of diagnoses that predispose to RhD alloimmunization enables better utilization of RhD-negative RBCs during times of shortage.

First trimester noninvasive fetal RHD genotyping using maternal dried blood spots.

OBJECTIVE: This study was aimed to evaluate whether maternal dried blood spots could be a potential source for the noninvasive fetal RHD genotyping, serving as a combined one-step test for both the First Trimester Screen and the fetal RHD genotyping. METHOD: Both the maternal dried blood spots and the peripheral blood samples from 19 RhD-negative pregnant women were obtained during the First Trimester Screen. DNA was extracted and sequential real-time PCRs were performed to determine the fetal RHD genotypes. Fetal RhD serological types were obtained after delivery. This study was approved by the Institutional Review Board, and informed consents were obtained. RESULTS: A total of 19/19 fetal RHD genotyping with maternal DBS were consistent with the follow-up serological RhD test results after birth. Eleven were RhD positive, and eight were RhD negative (RHD deletion or RHD-CE-D = 6, RHD pseudogene = 1, RHDVI = 1). Sensitivity = 100%, specificity = 100%, positive predictive value = 100%, negative predictive value = 100%. A total of 18/19 fetal gender were determined correctly with maternal DBS. One female fetus was falsely determined as male. Sensitivity = 100%, specificity = 91.6%, positive predictive value = 87.5%, negative predictive value = 100%. CONCLUSION: Maternal dried blood spots, with the benefits of flexible sample transportation and processing, could be utilized for the noninvasive prenatal fetal RHD genotyping and potentially be incorporated into the routine First Trimester Screen. Larger scale study is in progress to implement fetal RHD genotyping in routine prenatal care. © 2017 John Wiley & Sons, Ltd.

Third trimester screening for alloimmunisation in Rhc-negative pregnant women: evaluation of the Dutch national screening programme.

OBJECTIVE: To evaluate the effect of red blood cell (RBC) antibody screening in the 27th week of pregnancy in Rhc-negative women, on detection of alloimmunisation, undetected at first trimester screening ('late' alloimmunisation), and subsequent haemolytic disease of the fetus and newborn (HDFN), to assess risk factors for late alloimmunisation. DESIGN: Prospective cohort and nested case-control study. SETTING: The Netherlands. POPULATION: Two-year nationwide cohort. METHODS: Prospective inclusion of Rhc-negative women with negative first trimester screening and of screen-negative controls. Assessment of incidence and numbers needed to screen (NNS) of late alloimmunisation and HDFN; logistic regression analysis to establish risk factors for late alloimmunisation. MAIN OUTCOME MEASURES: Late alloimmunisation, HDFN. RESULTS: Late alloimmunisation occurred in 99 of 62 096 (0.159%) Rhc-negative women; 90% had c/E antibodies and 10% non-Rhesus antibodies. Severe HDFN (fetal/neonatal transfusion) occurred in two of 62 096 (0.003%) of Rhc-negative women and 2% of late alloimmunisations; moderate HDFN (phototherapy) occurred in 20 children [22.5%; 95% confidence interval (CI), 13.8-31.1%]. Perinatal survival was 100%. The NNS to detect one HDFN case was 2823 (31 048 for severe, 3105 for moderate HDFN). Significant risk factors were former blood transfusion [odds ratio (OR), 10.4; 95% CI, 1.14-94.9], parity (P-1: OR, 11.8; 95% CI, 3.00-46.5; P > 1: OR, 7.77; 95% CI, 1.70-35.4) and amniocentesis/chorionic villus sampling during current pregnancy (OR, 9.20; 95% CI, 1.16-72.9). CONCLUSIONS: Additional screening of Rhc-negative women improved the detection of late alloimmunisation and HDFN, facilitating timely treatment, with a NNS of 2823. Independent risk factors for late alloimmunisation were blood transfusion, parity and chorionic villus sampling/amniocentesis in the current pregnancy. The occurrence of most factors before the current pregnancy suggests a secondary immune response explaining most late alloimmunisations. TWEETABLE ABSTRACT: Third trimester screening for alloimmunisation in Rhc-neg women improves detection and treatment of severe HDFN.

Alloimmunization against platelets, granulocytes and erythrocytes in multi-transfused patients in Iranian population.

BACKGROUND: This study aims at alloantibody screening, determination of the types of these antibodies in multiple-transfused patients with chronic hematologic diseases. PATIENTS AND METHODS: This descriptive study was performed on 240 patients with chronic hematological diseases referred to public hospitals in Iran. Single blood sample was taken and tested for the presence of antibodies. In case of a positive antibody screening, antibody identification was performed using granulocyte agglutination test (GAT), granulocyte indirect immunofluorescence test (GIIFT), platelet indirect immunofluorescence test (PIIFT), monoclonal antibody-specific immobilization of platelet antigen (MAIPA) and panel cells. RESULTS: Out of 240 patients, 105 patients (43.75 %) had been alloimmunized. The incidence of alloantibodies against red blood cells (RBCs) in positive alloantibodies patients were 84.76% (89/105). The most common alloantibody was against antigens of the kell (anti-K) and Rh (anti-E) and (anti D) systems (46.66%, 18.09% and 11.43% respectively). The overall incidence of anti- human leukocyte antigen (HLA) antibodies were 65.7% (69/105). Polymorphonuclear (PMN)-specific antibodies were found in 6.66% (7/105). Also from 105 patients, 14 patients had alloantibodies against platelet. DISCUSSION: In general, it is recommend that to decrease the rate of alloantibody synthesis, the packed cells should be cross matched for minor blood groups especially for Rh (E) and kell. In addition, the use of leukodepleted blood products can decrease the frequency of alloimmunization against platelet (PLT), PMN and HLA antigens.

Evaluation of different testing methods for identification of RhIG in red blood cell antibody detection.

BACKGROUND: RhIG has had great success in protecting fetuses from potential harm; however, little work has been done to demonstrate how long RhIG reactivity is detected in the mother after administration when using common red blood cell antibody detection methods. STUDY DESIGN AND METHODS: A retrospective investigation was performed examining positive antibody identification panels due to RhIG. These panels were run on solid-phase (SP) testing. The time to a positive result, length of detection, and positive strength of reactivity (PSR) were evaluated. Additionally, a comparative study was performed evaluating how sensitive SP, gel (GT), and tube testing (TT) were at detecting RhIG using serially diluted plasma samples spiked with different RhIG formulas. RESULTS: Retrospectively, most antibody identification panels by SP were positive 3.5 months after RhIG administration and demonstrated a strong PSR. The longest recorded positive panel was present at 4.5 months. RhIG administered intramuscularly could not be detected until several hours after injection. The comparative study showed that SP was the most sensitive method while GT and TT were comparable to one another in detecting RhIG. SP also recorded strong PSR at very low concentrations of RhIG. GT and TT recorded weak PSR even with higher concentrations of RhIG. CONCLUSION: SP is the most sensitive testing method and has the ability to detect RhIG 4 to 5 months after administration. TT and GT have the ability to detect RhIG up to 3 to 4 months after administration. Different RhIG formulas may show slightly different lengths of detection.

Use of cffDNA to avoid administration of anti-D to pregnant women when the fetus is RhD-negative: implementation in the NHS.

OBJECTIVE: To determine whether a policy of offering cffDNA testing to all RhD-negative women at about 16 weeks' gestation to avoid anti-D administration when the fetus is RhD-negative could be implemented successfully in the NHS without additional funding. DESIGN: Prospectively planned observational service implementation pilot and notes audit. SETTING: Three maternity services in the South West of England. POPULATION: All RhD-negative women in a 6-month period. METHODS: Prospective, intervention, cross-sectional observational study, using pre-intervention data as controls. MAIN OUTCOME MEASURES: Proportion of suitable women who offered and accepted the test. Accuracy of the cffDNA result as assessed by cord blood group result. Fall in anti-D doses administered. RESULTS: 529 samples were received; three were unsuitable. The results were reported as RhD-positive (n = 278), RhD-negative (n = 185) or inconclusive, treat as positive (n = 63). Cord blood results were available in 502 (95%) and the only incorrect result was one case of a false positive (cffDNA reported as positive, cord blood negative - and so given anti-D unnecessarily). The notes audit showed that women who declined this service were correctly managed and that anti-D was not given when the fetus was predicted to be RhD-negative. The total use of anti-D doses fell by about 29% which equated to about 35% of RhD-negative women not receiving anti-D in their pregnancy unnecessarily. CONCLUSIONS: We recommend this service is extended to all UK NHS services.

Severe Rh alloimmunization and hemolytic disease of the fetus managed with plasmapheresis, intravenous immunoglobulin and intrauterine transfusion: A case report.

Rh alloimmunization remains a potentially devastating complication of pregnancy, with fetal anemia causing hydrops and intrauterine death. Intrauterine transfusion is the standard treatment, but is particularly dangerous before 20 weeks gestation. When the need for intrauterine transfusion is anticipated early in pregnancy, immune-modulating therapies such as plasmapheresis and IVIG have been used to delay transfusion to a later gestational age. We report a 35-year-old G5P1 Rh(D)-negative woman with severe Rh alloimmunization managed successfully with sequential plasmapheresis, intravenous immune globulin and intrauterine transfusion. The optimal plasmapheresis treatment protocol and incremental benefit of IVIG remains unknown.

Successful treatment of severe rhesus D-incompatible pregnancy with repeated double-filtration plasmapheresis.

Fetal anemia is caused by Rhesus (RhD) sensitization as a result of RhD incompatibility during pregnancy. The severe form of this disease can cause hydrops fetalis leading to intrauterine death. We experienced a highly sensitized 39-year-old woman with B Rh-negative blood. She had a history of three induced abortions and experienced perinatal death associated with hydrops fetalis. During the pregnancy prior to her most recent one, she was treated with double-filtration plasmapheresis (DFPP), high dose γ-globulin and intrauterine fetal blood transfusion (IUT). For her most recent pregnancy, we performed only weekly or fortnightly DFPP from 13 weeks until delivery. Anti-D antibody titer was maintained between 32 and 256 without any signs of fetal anemia. IUT was not required at any stage of the pregnancy. No adverse events were observed. She successfully delivered a healthy male infant weighing 2,289 g by Cesarean section at 35 weeks. Repeated DFPP may be an effective and safe strategy to reduce antibody titers in highly sensitized women with RhD-incompatible pregnancy, avoiding the need for IUT.

Routine administration of Anti-D: the ethical case for offering pregnant women fetal RHD genotyping and a review of policy and practice.

BACKGROUND: Since its introduction in the 1960s Anti-D immunoglobulin (Anti-D Ig) has been highly successful in reducing the incidence of haemolytic disease of the fetus and newborn (HDFN) and achieving improvements to maternal and fetal health. It has protected women from other invasive interventions during pregnancy and prevented deaths and damage amongst newborns and is a technology which has been adopted worldwide. Currently about one third of pregnant women with the blood group Rhesus D (RhD) negative in the UK (approximately 40,000 women per year in England and Wales), receive antenatal Anti-D Ig in pregnancy when they do not require it because they are carrying a RhD negative fetus. Since 1997, a test using cell free fetal DNA (cffDNA) in maternal blood has been developed to identify the genotype of the fetus and can be used to predict the fetal RhD blood group. DISCUSSION: This paper considers whether it is ethically acceptable to continue administering antenatal Anti-D Ig to all RhD negative women when fetal RHD genotyping using maternal blood could identify those women who do not need this product. SUMMARY: The antenatal administration of Anti-D Ig to a third of RhD negative pregnant women who carry a RhD negative fetus and therefore do not need it raises important ethical issues. If fetal RHD genotyping using maternal blood was offered to all RhD negative pregnant women it would assist them to make an informed choice about whether or not to have antenatal Anti-D Ig.

[Maternal blood intrauterine transfusions in the therapy of red-cell alloimmunization performed in three difficult cases]. / Wykorzystanie krwi matczynej do transfuzji doplodowych w terapii konfliktu serologicznego na przykladzie trzech trudnych przypadków.

Maternal alloimmunization can lead to hemolytic anemia, hydrops fetalis and even fetal or neonatal death. Intrauterine treatment is possible and effective even though it is associated with some risk. We present a rare method of maternal blood intrauterine transfusions in the therapy of three difficult cases of erythroblastosis fetalis. The aim of this report was to present an alternative to volunteer donors. In severe cases, i.e. in the absence of matching blood types from the donor in the presence of multiple alloantibodies in the pregnant woman or if multiple transfusions are required, this can be the only therapeutic option. To the best of our knowledge, this has been the first publication on maternal blood donation for intrauterine transfusion in the Polish literature.

Anti-Rh(c), "little c," isoimmunization: the role of rHuEpo in preventing late anemia.

The overall prevalence of non-Rh-D isoimmunization seems to lie between 0.15% and 1.1%. Anti-Rh(c) alloimmunization, "little c," occurs in 0.07% of pregnancies and shows a quite broad clinical presentation. Late anemia is a frequent problem occurring in the setting of isoimmunization. It occurs more frequently after intrauterine blood transfusions or exsanguinotransfusion, and it can be thought as a hyporegenerative anemia. The authors describe the use of human recombinant erythropoietin in preventing late anemia in a case of anti-Rh(c) isoimmunization. The use of human recombinant erythropoietin is a valid tool for preventing late-onset anemia due to either anti-Rh-D or non-anti-Rh-D isoimmunization.

Prediction of the rate of decline in fetal hemoglobin levels between first and second transfusions in red cell alloimmune disease.

OBJECTIVE: To determine variables that predict the rate of decline in fetal hemoglobin levels in alloimmune disease. METHOD: Retrospective review of singleton pregnancies that underwent first and second intrauterine transfusions for treatment of fetal anemia because of maternal Rh alloimmunization in a tertiary referral center. RESULTS: Forty-one first intrauterine transfusions were performed at 26.1 weeks (standard deviation, SD, 4.6), mean volume of blood transfused was 44.4 mL (SD 23.5) and estimated feto-placental volume expansion was 51.3% (SD 14.5%). Between first and second transfusion, hemoglobin levels reduced on average 0.40 g/dl/day (SD 0.25). Stepwise multiple regression analysis demonstrated that this rate significantly correlated with hemoglobin levels after the first transfusion, the interval between both procedures, and middle cerebral artery systolic velocity before the second transfusion. CONCLUSION: The rate of decline in fetal hemoglobin levels between first and second transfusions in alloimmune disease can be predicted by a combination of hemoglobin levels after the first transfusion, interval between both procedures, and middle cerebral artery systolic velocity before the second transfusion.

Pharmacokinetics of 250 µg anti-D IgG in the third trimester of pregnancy: an observational study.

OBJECTIVE: We present a pharmacokinetic study evaluating a single intramuscular dose of 250 µg anti-D immunoglobulin in the third trimester of pregnancy. The aim of the study was to determine the kinetic profile and duration of detectable levels of anti-D. DESIGN: Prospective observational study. SETTING: Antenatal outpatient clinic. POPULATION: Healthy Rhesus D (RhD)-negative pregnant women with an RHD-positive fetus. METHODS: Serial plasma anti-D quantitations following antenatal administration of anti-D immunoglobulin were performed using flow cytometry. Kinetic profiles for anti-D levels were generated from the concentration values at predetermined sampling time points. The half-lives were calculated by linear regression analysis. Main outcome measures. Time vs. concentration profile, half-life and anti-D concentration ≥1 ng/mL close to term. RESULTS: The maximal plasma concentration of anti-D was usually seen at 3-10 days postinjection, with a median value of 25 ng/mL. The half-life varied between individuals, with a median of 23 days. We found detectable levels of anti-D IgG within two weeks of parturition in 11 of 12 women. CONCLUSIONS: The preparation of anti-D immunoglobulin used in the present study, if administrated in pregnancy week 28-30, is associated with detectable levels of anti-D in most women at the time of delivery. Although the half-time is 23 days, it is uncertain whether all mothers have adequate anti-D concentrations at term. Alternative strategies may be evaluated in the future, with repeated administration of antenatal prophylaxis at term rather than conventional postpartum administration of anti-D.

Noninvasive fetal blood group genotyping of rhesus D, c, E and of K in alloimmunised pregnant women: evaluation of a 7-year clinical experience.

OBJECTIVE: To evaluate the diagnostic performance of noninvasive fetal blood group genotyping. DESIGN: Descriptive analysis. SETTING: Dutch national reference laboratory for pregnancies complicated by alloimmunisation. POPULATION: All consecutive alloimmunised pregnant women for whom fetal blood group genotyping of rhesus D, c, E or of K in maternal plasma was performed from 2003 up to 2010. METHODS: The test results of each individual assay were collected. Real-time polymerase chain reaction was performed for RHD exon 5 and RHD exon 7, or the specific allele of the RHCE or KEL gene. A stringent diagnostic algorithm was applied. In the case of a negative result, the presence of fetal DNA was ascertained by the analysis of the Y chromosome-specific SRY gene or other paternal genetic markers. Results were compared with available serology after birth or genotyping results of amniotic fluid cells. MAIN OUTCOME MEASURES: Percentage of conclusive test results and diagnostic accuracy. RESULTS: A total of 362 tests was performed (D: n = 168; c: n = 49; E: n = 85; K: n = 60). The median gestational age was 17 weeks (range 7-38 weeks). In 351 women (97%), a test result was issued: in seven samples, the presence of fetal DNA could not be confirmed; in two samples, non-specific amplification in the K assay led to an inconclusive result; in two samples, a maternal silent RHD gene prevented fetal RHD genotyping. No false-positive or false-negative results were found among those women for whom cord blood serology or genotyping results of amniotic fluid cells were available (n = 212). CONCLUSIONS: Noninvasive fetal blood group genotyping is accurate and applicable in a clinical diagnostic setting.