OBJECTIVE: To perform cost analyses of foregoing RhD blood type testing and administration of Rh immunoglobulin (RhIg) for bleeding in pregnancy at <12 weeks gestation in the United States.
METHODS: We created a decision-analytic model comparing the current standard treatment pathway for patients who have threatened, spontaneous, or induced abortion in the United States, with a new pathway foregoing RhD testing and administration of RhIg for those who are RhD-negative at <12 weeks gestation, assuming that the risk of sensitization is 0%. We derived population and cost estimates from the current literature and calculated the number needed to treat (NNT) and number needed to screen to avoid one case of fatal hemolytic disease of the fetus and newborn. We performed sensitivity analyses assuming Rh-sensitization risks of 1.5% and 3% and varying the subsequent pregnancy rates from 44% to 100%.
RESULTS: The annual savings to health care payers in the United States of foregoing RhD testing and RhIg administration with bleeding events at <12 weeks are $5.5 million/100,000 total pregnancies, assuming the sensitization risk is 0%. In sensitivity analyses with a sensitization risk of 1.5% and subsequent pregnancy rate of 84.3% foregoing Rh testing and RhIg administration would save $2.8 million/100,000 pregnancies, with a NNT of 7322 and a number needed to screen of 48,816. At a 3% sensitization rate, the current standard treatment pathway is most economical.
CONCLUSIONS: There is an opportunity to save as much as $5.5 million/100,000 pregnancies by withholding RhIg in specific situations and conserving it for use later in pregnancy.
CONCLUSIONS: Cost analyses support foregoing RhD blood type screening and RhIg administration at <12 weeks gestation if the sensitization rate is <3%. By deimplementing this low-value care, payers in the United States can save as much as $5.5 million/100,000 pregnancies and conserve RhIg for use later in pregnancy.

OBJECTIVE: To evaluate the knowledge of pregnant women and the clinical management of hemolytic disease of the fetus and newborn, as well as to describe the gestational profile, risk factors and socio-epidemiological profile of pregnant women treated at two municipal health units in Belém (Pará, Brazil).
METHODS: This was a cross-sectional analytical study, which consisted in the application of questionnaires to pregnant women who underwent prenatal care at the municipal health units.
RESULTS: A total of 104 pregnant women were evaluated; most were aged between 24 and 29 years old, had high school degrees (38 %), family incomes between 1 and 2 minimum wages (45 %) and blood type O+ (43 %). Regarding the gestational profile, the participants were predominantly in the third trimester of pregnancy (49 %), started prenatal care in the first gestational trimester (81 %) and were primiparous (61 %). Failures in the management of prenatal care were observed, especially with regard to access to information about the disease, since most pregnant women did not receive information about blood incompatibility during prenatal care. This led to limited knowledge about the pathology of the disease evidenced by the fact that most of the correct answers were between Questions 0-4, which were significantly associated with the women\'s education and income.
CONCLUSIONS: Although hemolytic disease of the fetus and newborn is serious, the pregnant women in this study demonstrated little knowledge about the disease and had inadequate care by health professionals, reinforcing the importance of improving care for women\'s health and prenatal care.

Anti-PP1PK alloimmunization is rare given ubiquitous P1PK expression. Prevention of recurrent miscarriages and hemolytic disease of the fetus and newborn (HDFN) in pregnant individuals with anti-PP1PK antibodies has relied upon individual reports. Here, we demonstrate the successful management of maternal anti-PP1PK alloimmunization in a 23-year-old, G2P0010, with therapeutic plasma exchange (TPE), intravenous immunoglobulin (IVIG), and monitoring of anti-PP1Pk titers. Twice-weekly TPE (1.5 plasma volume [PV], 5% albumin replacement) with weekly titers and IVIG (1 g/kg) was initiated at 9 weeks of gestation (WG). The threshold titer was ≥16. Weekly middle cerebral artery-peak systolic velocities (MCA-PSV) for fetal anemia monitoring was initiated at 16 WG. PVs were adjusted throughout pregnancy based on treatment schedule, titers, and available albumin. Antigen-negative, ABO-compatible RBCs were obtained through the rare donor program and directed donation. An autologous blood autotransfusion system was reserved for delivery. Titers decreased from 128 to 8 by 10 WG. MCA-PSV remained stable. At 24 WG, TPE decreased to once weekly. After titers increased to 32, twice-weekly TPE resumed at 27 WG. Induction of labor was scheduled at 38 WG. Vaginal delivery of a 2950 g neonate (APGAR score: 9, 9) occurred without complication (Cord blood: 1+ IgG DAT; Anti-PP1Pk eluted). Newborn hemoglobin and bilirubin were unremarkable. Discharge occurred postpartum day 2. Anti-PP1Pk alloimmunization is rare but associated with recurrent miscarriages and HDFN. With multidisciplinary care, a successful pregnancy is possible with IVIG and TPE adjusted to PV and titers. We also propose a patient registry and comprehensive management plan.

BACKGROUND: We report an obstetric case involving an RhD-positive woman who had developed a red blood cell (RBC) antibody that was not detected until after delivery of a newborn, who presented with a positive direct antiglobulin test result. Immunohematology studies suggested that the maternal antibody was directed against a low-prevalence antigen on the paternal and newborn RBCs.
RESULTS: Comprehensive blood group profiling by targeted exome sequencing revealed a novel nonsynonymous single nucleotide variant (SNV) RHCE c.486C>G (GenBank MZ326705) on the RHCE*Ce allele, for both the father and newborn. A subsequent genomic-based study to profile blood groups in an Indigenous Australian population revealed the same SNV in 2 of 247 individuals. Serology testing showed that the maternal antibody reacted specifically with RBCs from these two individuals.
CONCLUSIONS: The maternal antibody was directed against a novel antigen in the Rh blood group system arising from an RHCE c.486C>G variant on the RHCE*Ce allele linked to RHD*01. The variant predicts a p.Asn162Lys change on the RhCE protein and has been registered as the 56th antigen in the Rh system, ISBT RH 004063.
CONCLUSIONS: This antibody was of clinical significance, resulting in a mild to moderate hemolytic disease of the fetus and newborn (HDFN). In the past, the cause of such HDFN cases may have remained unresolved. Genomic sequencing combined with population studies now assists in resolving such cases. Further population studies have potential to inform the need to design population-specific red cell antibody typing panels for antibody screening in the Australian population.

Hemolytic disease of the fetus and newborn (HDFN) may cause severe cholestasis with direct bilirubin concentrations reaching up to 50 times the upper limit of normal. This case report describes twins whose highest direct bilirubin concentrations were 32.2 mg/dL and 50.2 mg/dL, with no significant signs of hepatic impairment. The index pregnancy was complicated by Rhesus factor immunization with anti-D antibodies present in maternal serum, which caused fetal anemia requiring intrauterine blood transfusions. Complementary tests demonstrated Rhesus D alloimmunization as the sole cause of cholestasis. To the best of our knowledge, this is the first study to describe such elevated direct bilirubin concentrations caused by HDFN.

BACKGROUND: Low-titer group O whole blood (LTOWB) for treatment of hemorrhagic shock sometimes necessitates transfusion of RhD-positive units due to short supply of RhD-negative LTOWB. Practitioners must choose between using RhD-positive LTOWB when RhD-negative is unavailable against the risk to a female of childbearing potential of becoming RhD-alloimmunized, risking hemolytic disease of the fetus and newborn (HDFN) in future children, or using component therapy with RhD-negative red cells. This survey asked females with a history of red blood cell (RBC) alloimmunization about their risk tolerance of RhD alloimmunization compared to the potential for improved survival following transfusion of RhD-positive blood for an injured RhD negative female child.
METHODS: A survey was administered to RBC alloimmunized mothers. Respondents were eligible if they were living in the United States with at least one red cell antibody known to cause HDFN and if they had at least one RBC alloimmunized pregnancy.
RESULTS: Responses from 107 RBC alloimmmunized females were analyzed. There were 32/107 (30%) with a history of severe HDFN; 12/107 (11%) had a history of fetal or neonatal loss due to HDFN. The median (interquartile range) absolute improvement in survival at which the respondents would accept RhD-positive transfusions for a female child was 4% (1%-14%). This was not different between females with and without a history of severe or fatal HDFN (p = .08 and 0.38, respectively).
CONCLUSIONS: Alloimmunized mothers would accept the risk of D-alloimmunization in a RhD-negative female child for improved survival in cases of life-threatening bleeding.

Deep sequencing by NGS of targeted amplicons can identify rare genetic variants in a pool of DNA where the vast majority of genomic DNA does not contain the variant. This approach can be used to detect a previously described paternally inherited, fetal variant in cell-free DNA (cfDNA) in maternal plasma. This is useful in cases where risk for the fetus is contingent upon inheritance of a paternal variant that the woman does not have. Both pathogenic and non-pathogenic variants that the woman does not have can be detected. In cases of compound heterozygosity, presence of the paternal pathogenic variant also requires detection of the maternal variant for risk assessment, which requires a chorion villus biopsy.We have used this approach to focus on detection of fetal blood groups in cases of presence of maternal alloantibodies against blood group antigens in pregnancy, to predict whether the fetus has inherited a blood group antigen that is targeted by the alloantibodies. In cases of maternal alloantibodies against blood group antigens, the fetus is at risk of hemolytic disease of the fetus and newborn (HDFN). With a known specificity of the maternal antibodies and if the fetal blood group can be determined in the pregnancy, then it can be ascertained if the fetus is at risk of HDFN and rational pregnancy care can be instituted. A noninvasive procedure avoids risks for the fetus. We have reported a procedure based on NGS analysis of PCR amplified cfDNA from maternal plasma. Some fetuses may die as early as week 18. We use this approach to predict fetal K, k, RhC, Rhc, RhE, and ABO blood groups in cases with a risk of HDFN due to the corresponding maternally produced antibodies.The NGS-based analysis can predict the presence or absence of incompatible antigens on the fetal RBCs.In this chapter, a noninvasive method for predicting some fetal blood groups early in pregnancy is described. There is a clinical need for such assays, and they may be a useful tool for management of pregnancies complicated by these alloantibodies within the field of precision medicine.

BACKGROUND: Prehospital low-titer group O whole blood (LTOWB) used for patients with life-threatening hemorrhage is often RhD positive. The most important complication following RhD alloimmunization is hemolytic disease of the fetus and newborn (HDFN). Preceding clinical use of RhD positive LTOWB, we estimated the risk of HDFN due to LTOWB prehospital transfusion in the Finnish population.
METHODS: We collected data on prehospital transfusions in Tampere and Helsinki University Hospital areas. Using the mean of reported alloimmunization rates in trauma studies (24%) and a higher reported rate representing trauma patients of 13-50 years old (42.7%), we estimated the risk of HDFN and extrapolated it to the whole of Finland.
RESULTS: We estimated that in Finland, with the current prehospital transfusion rate we would see 1-3 cases of severe HDFN due to prehospital LTOWB transfusions every 10 years, and fetal death due to HDFN caused by LTOWB transfusion less than once in 100 years.
CONCLUSIONS: The estimated risk of serious HDFN due to prehospital LTOWB transfusion in the Finnish population is similar to previous estimates. As Finland routinely screens expectant mothers for red blood cell antibodies and as the contemporary treatment of HDFN is very effective, we support the prehospital use of RhD positive LTOWB in all patient groups.

Hemolytic Disease of the Fetus and Newborn (HDFN) is a condition that affects 1 to 2 out of 1000 patients during pregnancy (1). When an alloantibody is present, it is essential to identify its nature in order to organize appropriate follow-up. Kell-mediated HDFN is rare; it occurs in about 5% of Kell alloimmunized pregnant women. It is important to note that in case of anti-Kell immunization, the severity of HDFN is not correlated with maternal antibody titers, and anemia tends to occur earlier and more severely. Therefore, early diagnosing and management of this condition is crucial. In the management of severe fetal anemia due to Kell immunization, available treatments include in utero transfusion (IUT), immunoglobulin therapy. Other alternative treatments exist, such as plasmapheresis. Intravenous immunoglobulin (IVIG), a noninvasive therapeutic approach, acts through multiple mechanisms. IVIG has been evaluated in cases of RhD immunization with high maternal antibody titers and a history of pregnancies involving early hydrops or intrauterine death. Regarding the potential benefits of intravenous IgG therapy, it may delay the need for early IUT, reduce the overall reliance on IUT, and have a positive impact on obstetric outcomes. This case of IV IgG therapy of anti-Kell immunization offers a thought-provoking avenue for future exploration.

The current recommended testing algorithm for assessing the alloimmunized pregnancy utilized by many obstetricians in the United States (US) fails to consider the most recent evidence, placing fetuses, and mothers at unnecessary risk of poor outcome or death. This narrative review of the current landscape of fetal red blood cell (RBC) antigen testing evaluates the history of hemolytic disease of the fetus and newborn (HDFN) and how its discovery has continued to influence practices in the US today. We compare current US-based HDFN practice guidelines with those in Europe. We also provide transfusion medicine and hematology perspectives and recommendations addressing the limitations of US practice, particularly regarding paternal RBC antigen testing, and discuss the most valuable alternatives based on decades of data and evidence-based recommendations from Europe.