Non-invasive tests to predict fetal anemia in Kell-alloimmunized pregnancies

Non-RhD alloimmunization in pregnancy: an updated review

RhD alloimmunization in pregnancy is still the main cause of hemolytic disease of the fetus and neonate (HDFN). Nevertheless, there are other antigens that may be associated with the occurrence of this phenomenon and that have been growing in proportion, given that current prevention strategies focus only on anti-RhD antibodies. Although not widespread, the screening and diagnostic management of the disease caused by these antibodies has recommendations in the literature. For this reason, the following review was carried out with the objective of listing the main red blood cell antigen groups described - such as Rh, ABO, Kell, MNS, Duffy, Kidd, among others - addressing the clinical importance of each one, prevalence in different countries, and recommended management when detecting such antibodies during pregnancy.

The role of measuring peak systolic velocity of the middle cerebral artery blood flow and anti-K1 titre during pregnancy to detect foetuses with severe anaemia, foetal hydrops, and the requirement of intrauterine transfusion: A systematic review and meta-analysis

The clinical manifestation of foetal anaemia caused by maternal Kell alloantibodies differs from that caused by non-Kell alloantibodies. Severe anaemia develops in the foetus in the early weeks of gestation; therefore, proper management and early intervention are important. A systematic review and meta-analysis was performed to determine whether the anti-K1 titre can determine the sequelae of Kell alloimmunised pregnancies. Prospective and retrospective cohort studies were used to conduct a systematic review following a comprehensive literature search, in accordance with the Preferred Reporting Items for Systematic Review and Meta-Analysis (PRISMA) guidelines. Studies were screened based on a defined set of inclusion and exclusion criteria. A total of 5143 potential articles were identified. Ten studies were used in the meta-analysis of pregnancy outcomes for a specific anti-K1 titre cut-off. The meta-analysis identified statistical significance for intrauterine transfusion (ARD: 0.351; 95 % CI: 0.593-0.109; p-value = 0.004), hydrops (ARD: 0.808; 95 % CI: 1.145-0.472; p-value <0.001), intrauterine foetal death (ARD: 0.938; 95 % CI:1.344 to -0.533; p-value <0.001) and intrauterine transfusion for Doppler middle cerebral artery >1.5 MoM (ARD: 0.381; 95 % CI:1.079 to -0.317; p-value = 0.285). It was concluded that there is no correlation between anti-K1 titre and Kell sensitised pregnancy outcomes, but monitoring the anti-K1 titre is important to manage the pregnancy and it helps clinicians determine the need for intrauterine transfusions. Doppler middle cerebral artery peak systolic velocity is strongly correlated with foetal anaemia and is an efficient routine method for determining the need for intrauterine transfusions in pregnancies affected by anti-K1.

Current Insights Into K-associated Fetal Anemia and Potential Treatment Strategies for Sensitized Pregnancies

K-associated anemic disease of the fetus and newborn (K-ADFN) is a rare but life-threatening disease in which maternal alloantibodies cross the placenta and can mediate an immune attack on fetal red blood cells expressing the K antigen. A considerably more common disease, D-associated hemolytic disease of the fetus and newborn (D-HDFN), can be prophylactically treated using polyclonal α-D antibody preparations. Currently, no such prophylactic treatment exists for K-associated fetal anemia, and disease is usually treated with intrauterine blood transfusions. Here we review current understanding of the biology of K-associated fetal anemia, how the maternal immune system is sensitized to fetal red blood cells, and what is understood about potential mechanisms of prophylactic HDFN interventions. Given the apparent challenges associated with preventing alloimmunization, we highlight novel strategies for treating sensitized mothers to prevent fetal anemia that may hold promise not only for K-mediated disease, but also for other pathogenic alloantibody responses.

Diagnostic Performance of Doppler Ultrasonography for the Detection of Fetal Anemia: A Meta-analysis

This study evaluates the diagnostic performance of Doppler ultrasound in diagnosing fetal anemia. Data were taken from relevant study reports published in peer-reviewed journals identified after a literature search in electronic databases. Random effects meta-analyses were performed by pooling the effect sizes of diagnostic indices (sensitivity, specificity, positive/negative predictive values, and false-positive rate) or correlation coefficients reported by individual studies. As a result, 31 studies (1848 pregnancies; gestation age, 28.25 weeks [95% confidence interval {CI}, 26.87-29.63]) were included in the meta-analysis. Anemia was found in 63.7% (95% CI, 49.7-77.7) fetuses, and severe anemia was found in 36.7% (95% CI, 26.9-46.4) fetuses. Sensitivity and specificity of Doppler ultrasound for detecting fetal anemia in alloimmunized fetuses at middle cerebral artery peak systolic velocity cutoff of 1.5 multiple of median for gestation age were 83.42% (95% CI, 71.75-95.09) and 80.30% (95% CI, 73.58-87.02), respectively. Positive predictive value, negative predictive value, and false-positive rate were 76.35% (95% CI, 65.98-86.72), 80.0% (95% CI, 76.63-83.37), and 10.4% (95% CI, 5.9-14.9), respectively. Correlation coefficient between hematological anemia and Doppler ultrasound-measured blood flow velocity was -0.706 (95% CI, -0.765 to -0.635; P < 0.00001). In conclusion, Doppler ultrasound-measured middle cerebral artery peak systolic velocity at 1.5 multiple of median provides good diagnostic strength for the detection of alloimmunized fetal anemia. A strong correlation between Doppler velocimetric measures and hematological anemia is also observed.

The prenatal intervention of pregnancy complicated with anti-Kell isoimmunization: a review

Since the first case of the hemolytic disease of the fetus and newborn (HDFN) caused by anti-K was reported in 1946, the fetal diagnosis of K-HDFN has made rapid progress from invasive immunological and biochemical tests to noninvasive Doppler ultrasound and molecular biology techniques. However, its treatment, especially prenatal intervention, has developed slowly compared with RhD-HDFN. This review attempts to clarify the current key points and explore the direction of the next phase by systematically reviewing the development of diagnosis and treatment of this disease, which involving multidisciplinary participation.

Magnetic Resonance Imaging: A New Tool to Optimize the Prediction of Fetal Anemia?

INTRODUCTION

The false-positive rate in the prediction of fetal anemia is 10-15%. We investigated if a new, noninvasive MRI method used as a supplement to ultrasound could improve the prediction.

METHODS

Fetuses suspected of anemia and controls were scanned in a 1.5-tesla MRI scanner 1-4 times during pregnancy. Cases were scanned before and after intrauterine blood transfusion with a T1-mapping MRI sequence in a cross-section of the umbilical vein.

RESULTS

Inclusion of 8 cases and 11 controls resulted in 10 case scans (2 cases were included twice) and 33 control scans. In controls, the T1 relaxation time was 1,005-1,391 ms; in cases with severe anemia, 1,505-1,595 ms, moderate anemia 1,503-1,525 ms, and no/mild anemia 1,245-1,410 ms. After blood transfusions, values dropped to 1,123-1,288 ms. The mean value in moderate and severe anemic cases was 275 ms higher than in controls (95% CI 210-341 ms, p < 0.0001), and after blood transfusion it was comparable to controls (3 ms, 95% CI -62 to 68 ms, p = 0.934). A 1,450-ms cut-off would have identified all cases in need of blood transfusion with no false-positive cases.

CONCLUSIONS

Our findings indicate a potential for this new MRI method to improve the prediction of fetal anemia as a supplement to ultrasound.

An innovative test for non-invasive Kell genotyping on circulating fetal DNA by means of the allelic discrimination of K1 and K2 antigens

OBJECTIVE

The aim of this study was to present a new method for fetal Kell genotyping by means of the allelic discrimination of K1 and K2 in real-time polymerase chain reaction (PCR).

METHODS

Real-time quantitative polymerase chain reaction incorporating an allele-specific primer was developed for detecting the K allele of KEL.

RESULTS

By means of this method, the K1/K2 genotype was able to be determined in all blood samples analyzed. Results using cell-free fetal DNA (cffDNA) from two Kell-negative pregnant women confirmed the Kell-positive genotype of fetuses. The real-time PCR analysis also allowed the determination of the fetal fraction using the quantification of Kell-positive DNA.

CONCLUSION

An efficient and reliable strategy for Kell genotyping is herein presented. The method was optimized on cffDNA to create a non-invasive prenatal test which could be routinely used for the prevention of hemolytic disease of the fetus and the newborn (HDFN).

Intertwin discrepancy in middle cerebral artery peak systolic velocity and third-trimester fetal growth restriction in monochorionic-diamniotic twin pregnancy

OBJECTIVES

To assess the role of intertwin discrepancy in middle cerebral artery peak systolic velocity (MCA-PSV) for the prediction of late selective intrauterine growth restriction (sIUGR) at birth and birth weight discrepancy of > 25% (BW-25) in otherwise uncomplicated monochorionic-diamniotic (MCDA) twin pregnancies.

METHODS

This was a cohort study including all MCDA pregnancies followed in a tertiary fetal medicine unit between 2008 and 2013. Exclusion criteria were referral after first trimester, abnormal karyotype, structural anomalies, twin-to-twin transfusion syndrome, twin anemia-polycythemia sequence and sIUGR detected before 28 weeks. MCA-PSV values of both twins measured in the second trimester (18-24 weeks) and early third trimester (26-32 weeks) were converted in multiples of the median (MoM). sIUGR was defined as birth weight < 5(th) centile. The relationship between MCA-PSV discrepancy, sIUGR and BW-25 was assessed by logistic regression analysis. Receiver-operating characteristics (ROC) curves were used to ascertain the predictive value of MCA-PSV discrepancy for such complications.

RESULTS

In total, 136 MCDA twin pregnancies were included in the analysis. Thirty (22.1%) were complicated with sIUGR at birth and 12 (8.8%) were complicated with BW-25. Logistic regression analysis identified MCA-PSV discrepancy as an independent predictor for sIUGR. ROC curves identified third-trimester MCA-PSV discrepancy as the best predictor for both sIUGR (area under ROC curve (AUC), 0.73 (95% CI, 0.62-0.85)) and BW-25 (AUC, 0.79 (95% CI, 0.65-0.93)). The optimal cut-off point for MCA-PSV discrepancy was 0.30 MoM (sensitivity, 70% and specificity, 69% for sIUGR; sensitivity, 83% and specificity, 72% for BW-25).

CONCLUSION

In MCDA twin pregnancies, MCA-PSV discrepancy is associated with both sIUGR at birth and BW discordance. Copyright © 2015 ISUOG. Published by John Wiley & Sons Ltd.

Doppler in obstetrics: beyond the umbilical artery

Doppler analysis of the umbilical and uterine arteries has long been performed in perinatal medicine to assess fetal health and maternal risk for preeclampsia. Several other vessels can be interrogated to obtain additional, vital information. Velocimetry in the fetal middle cerebral artery can yield evidence of the presence or absence of anemia and, in cases of delayed growth, of the risk of hypoxic damage. Ductus venosus waveforms are a very good indicator of impeding fetal jeopardy and should be used when umbilical artery waveforms become abnormal. Early pregnancy uterine artery Doppler reflects the status of the placental vasculature and, as such, is an excellent tool for predicting the risk of preeclampsia or intrauterine growth restriction.

Hydrops Fetalis due to Kell Alloimmunization: A Perinatal Approach to a Rare Case

Objective: While routine administration of rhesus (Rh) immunoglobulin has significantly reduced the incidence of Rh alloimmunization, maternal alloimmunization to other red cell antigens remains a contributor to perinatal morbidity and mortality. Although the Kell antigen is seen on the red cells of only 9% of the general population, attention to Kell antibodies continues to increase.

Case Report: A case of fetal hydrops was sonographically detected at 30 weeks of gestation. Antenatal tests to evaluate the fetus’s condition clearly showed that the level of hemolytic disease was critical and the baby was delivered prematurely due to fetal distress. The combination of anemia, reticulocytopenia, hydrops fetalis, and a positive indirect Coombs test suggested Kell isoimmunization. The baby was successfully treated with exchange transfusion of Kellnegative packed red cells, and was discharged on postnatal d 30.

Conclusion: The presented case of hydrops fetalis was due Kell alloimmunization that was detected during the postnatal period, and thus we plan to discuss the perinatal approach to Kell immunization.

The MCA Doppler and its role in the evaluation of fetal anemia and fetal growth restriction

Doppler velocimetry of the middle cerebral artery (MCA) has played a major role in fetal medicine for the last 23 years, both in intrauterine growth-restricted (IUGR) and anemic fetuses. Its utility in the diagnosis and management of cases of fetal anemia was initially demonstrated in cases of red cell alloimmunization and later extended to other types of anemia. In addition, MCA Doppler studies are crucial in the evaluation of IUGR fetuses. This article is a review of the role of the MCA in these 2 conditions.

Assessment of the peak systolic velocity of the middle cerebral artery in twin-twin transfusion syndrome. Part I: preoperative assessment

OBJECTIVE

We sought to assess the incidence of an elevated peak systolic velocity of the middle cerebral artery (MCA-PSV) in twin-twin transfusion syndrome prior to laser surgery and its prognostic value for intrauterine fetal demise 24 hours after surgery (IUFD-24).

STUDY DESIGN

An elevated MCA-PSV was defined as a velocity > .5 multiples of the median by transabdominal pulsed Doppler. Gestational age, Quintero stage, and number and/or type of placental vascular anastomoses were assessed as risk factors for an elevated MCA-PSV. Risk of IUFD-24 was assessed relative to an elevated MCA-PSV.

RESULTS

An elevated MCA-PSV was present in 4.2% of donors, 3.2% of recipients (P = .5), and 1.5% of both twins in 189 patients with twin-twin transfusion syndrome. An elevated MCA-PSV was unrelated to gestational age, stage, and number or type of anastomoses. An elevated MCA-PSV in the recipient twin was associated with an increased risk of IUFD-24 of this fetus (P = .01).

CONCLUSIONS

An elevated MCA-PSV is present in < 5% of donor and recipient twins. An elevated MCA-PSV is a risk factor for IUFD-24 of the recipient twin.

Fetal anemia due to non-Rhesus-D red-cell alloimmunization

Although anti-RhD was once the major etiology of hemolytic disease of the fetus/newborn (HDFN), the widespread adoption of antenatal and postpartum Rhesus immune globulin has resulted in a marked decrease in the prevalence of alloimmunization to the RhD antigen in pregnancy. Maternal alloimmunization to other red cell antigens continues to play a role as the cause of fetal disease since no prophylactic immune globulins are available to prevent the formation of these antibodies. An increasing incidence of the Kell (anti-K1) antibody has been noted in the United States. Guidelines for intervention in cases of irregular red cell antibodies are limited by the bias of anecdotal reports in the literature in favor of severe cases of HFDN. Although most diagnostic protocols used in the management of the RhD-alloimmunized pregnancy can be applied in cases of non-RhD sensitization, Kell (K1 and K2) alloimmunization should be managed more conservatively.

Fetal anaemia as a cause of fetal injury: diagnosis and management

PURPOSE OF REVIEW

This review provides up-to-date information on the diagnosis and management of fetal anaemia.

RECENT FINDINGS

Exciting advances in the field of red blood cell isoimmunization are phasing out the need for invasive procedures. Rhesus blood group genotyping using fetal DNA in maternal plasma has been introduced into clinical practice with remarkable success. The role of middle cerebral artery peak systolic velocity in screening for fetal anaemia has been confirmed in various causes of fetal anaemia. A recent review of a successful Iran national screening programme for thalassaemia provided a timely and valuable educational opportunity. The value of intrauterine transfusion as a treatment for fetal anaemia was demonstrated by both high success rate and low procedure-related pregnancy loss rate.

SUMMARY

Fetal anaemia is one of the severe fetal conditions that affect the worldwide population. Rhesus isoimmunization remains an important health issue despite the recommendation for anti-D immunoglobulin prophylaxis and injection after sensitizing events. Noninvasive ultrasound diagnostic methods have replaced traditional invasive procedures in the assessment of fetus at risk of anaemia due to various causes, including red blood cell isoimmunization, parvovirus B19 infection and thalassaemia. The increased availability of intrauterine transfusion will help to improve the prognosis of these anaemic fetuses.

The usefulness of middle cerebral artery Doppler assessment in the treatment of the fetus at risk for anemia

The use of Doppler ultrasound evaluation to measure the peak systolic velocity of the fetal middle cerebral artery (MCA) has been a major breakthrough in the noninvasive detection of fetal anemia. An elevated peak MCA velocity of >1.5 multiples of the median is useful in the timing of the initial intrauterine transfusion (IUT) in the red cell-alloimmunized pregnancies. Data reported to date suggest that a threshold of 1.32 multiples of the median can be used to time the second IUT; the MCA Doppler evaluation does not appear sensitive for the timing of subsequent IUTs in these pregnancies. The peak MCA velocity has also proved useful in the detection of other anemic states that include Kell alloimmunization, fetal parvovirus infection, fetomaternal hemorrhage, alphathalassemia, and after-laser therapy for twin-twin transfusion.

Fetal anaemia: diagnosis and management

Fetal anaemia can by treated by in-utero therapy, which results in a significant improvement in perinatal outcome. The important causes of fetal anaemia are rhesus alloimmunisation, kell alloimmunisation and parvovirus infection. At-risk pregnancies require serial monitoring to ensure timely intervention with intrauterine transfusion. Non-invasive testing with middle cerebral artery Doppler is becoming the monitoring modality of choice.

Obstetric History and Antibody Titer in Estimating Severity of Kell Alloimmunization in Pregnancy

OBJECTIVE

To evaluate the usefulness of the obstetric history and the maternal serum Kell antibody titer in the management of pregnancies with Kell alloimmunization.

METHODS

In a retrospective cohort study of 41 pregnancies complicated by Kell alloimmunization, the obstetric history, divided into presence or absence of a previous Kell-positive child, and Kell antibody titers in the index pregnancy were correlated with the gestational age at the onset of fetal anemia.

RESULTS

Women with a previous Kell-positive child had a lower gestational age at the first intrauterine transfusion compared with those without a previous Kell-positive child (P=.01). However, in two of 29 pregnancies in the latter group, severe fetal anemia requiring transfusion was detected before 20 weeks of gestation. In neither group were maternal Kell antibody titers significantly correlated with gestational age at first intrauterine transfusion (P=.62 and P=.72, respectively). In all but two pregnancies (1:2 and 1:4, respectively), antibody titers were at least 1:32 before the first intrauterine transfusion.

CONCLUSION

For timely detection of all cases of severe fetal anemia, Kell-alloimmunized pregnancies with a Kell-positive fetus and titers greater than or equal to 1:2 should be closely monitored from 16 to 17 weeks of gestation onward.

High additional maternal red cell alloimmunization after Rhesus- and K-matched intrauterine intravascular transfusions for hemolytic disease of the fetus

OBJECTIVE

Intrauterine transfusion (IUT) is a life-saving therapy for the severely anemic fetus with hemolytic disease. However, maternal additional antibody formation is a complication of the procedure. In this study, we determined antibody formation after introduction of preventive Rh-D, -C, -c, -E, and -e and K matching of IUT donors.

STUDY DESIGN

This was a retrospective follow-up study.

RESULTS

During an 11-year period, 686 Rhesus- and K-matched IUTs were performed in 233 pregnancies and in 95% (652/686) posttransfusion antibody testing was performed after a median interval of 21 days. Twenty-five percent (53/212) of the women formed 64 new antibodies and, compared to our previous study, this incidence was not decreased by the use of Rhesus- and K-matched donors. After delivery, 72% (153/212) of the women had multiple RBC antibodies. Additional antibodies were in 48% (31/64) directed against Rhesus and K antigens, induced by the fetus, or as natural antibodies. In 52% (33/64) the antibodies were directed against non-Rhesus and -K antigens and in 65% (11/17) of eligible cases the IUT donor and not the fetus expressed the corresponding antigen(s).

CONCLUSION

Despite Rhesus- and K-matching, women treated with IUTs still show strikingly broad red cell alloimmunization. More extensive IUT donor red cell matching, including FY, JK, and S antigens, to reduce the formation of new red cell antibodies should be explored.

Management of Kell isoimmunization--evaluation of a Doppler-guided approach

OBJECTIVE

To assess the role of peak systolic velocity in the middle cerebral artery (MCA-PSV) in the management of pregnancies complicated by Kell isoimmunization.

METHODS

Sixteen fetuses were monitored by conventional protocol (Group 1) and eight fetuses by an MCA-PSV-guided protocol (Group 2). The conventional protocol included a weekly ultrasound evaluation and measurement of maternal anti-Kell titers every 4-6 weeks. In Group 2 Doppler assessment of the MCA-PSV was performed at intervals of 4 to 7 days and MCA-PSV>1.5 multiples of the median (MoM) was considered as an indication for fetal blood sampling (FBS).

RESULTS

No parameter emerged as a reliable predictor of isoimmunization severity in Group 1. In Group 2, no FBS was necessary in one case since the MCA-PSV values obtained during the follow-up were <1.29 MoM. In two cases the first FBS was already indicated after 1 week of follow-up, but five other fetuses were followed for 3-9 weeks before FBS was indicated. All fetuses with MCA-PSV>1.5 MoM prior to intrauterine transfusion (IUT) had severe fetal anemia on FBS. In fetuses with severe anemia on the first FBS, the MCA-PSV values 7 days before the first FBS were <1.29 MoM (four cases), between 1.29 and 1.5 MoM (two cases) and >1.55 MoM (one case).

CONCLUSIONS

In the management of Kell isoimmunization invasive procedures may be avoided by implementing MCA-PSV measurements. Delineation of appropriate intervals between reassessments, the reliability of MCA-PSV following repeated IUTs, and cut-off values for FBS await further study.

[Contribution of fetal middle cerebral artery peak systolic velocity in the management of non-immune hydrops]

Hydrops fetalis is associated with a wide variety of fetal and maternal disorders. Among these disorders, cases with anemia may benefit from a specific treatment. The authors report on two cases of hydrops fetalis with increased middle cerebral artery peak systolic velocity and discussed the contribution of this finding in the management of fetuses with hydrops.

First trimester ultrasound screening for fetal aneuploidy and middle cerebral artery Doppler assessment for fetal alloimmunization

PURPOSE OF REVIEW

Traditional methods of fetal evaluation require invasive procedures (e.g. amniocentesis) with an inherent, albeit low, risk of complications and pregnancy loss. As medical knowledge and ultrasound technology have advanced, noninvasive modes of fetal evaluation have become increasingly used. Two disorders in which this has been most applied are fetal aneuploidy and alloimmunization to red blood cell antigens.

RECENT FINDINGS

First-trimester screening protocols for fetal aneuploidy combine ultrasound measurement of the fetal nuchal translucency with the measurement of two maternal serum hormones, free beta-human chorionic gonadotropin and pregnancy-associated plasma protein-A. This combination detects approximately 85% of women pregnant with fetuses with trisomy 21. An increase in the velocity of fetal middle cerebral artery blood flow occurs in the setting of moderate to severe fetal anemia and can be measured with Doppler ultrasound. Middle cerebral artery evaluation is equally sensitive in the prediction of anemia as amniocentesis for bilirubin breakdown products and has less associated risk. It has an additional benefit because it can also be applied to causes of anemia other than hemolysis.

SUMMARY

Noninvasive methods of fetal assessment are becoming increasingly commonplace. There has been a dramatic decrease in the use of prenatal diagnostic services as screening strategies have become available. Doppler assessment of the velocity of blood flow through the fetal middle cerebral artery will allow for more judicious application of invasive procedures to pregnancies at significant risk for anemia.

Middle cerebral artery peak systolic velocity: is it the standard of care for the diagnosis of fetal anemia?

OBJECTIVE

The aim of this work was to review the use of middle cerebral artery peak systolic velocity (MCA PSV) for the diagnosis of fetal anemia.

METHODS

With the use of a computerized database (MEDLINE), articles on the diagnosis of fetal anemia with ultrasonography were reviewed. Other pertinent references were obtained from the references cited in these articles. In addition, my own institution's clinical experience of the past 18 years was reviewed.

RESULTS

Several ultrasonographic parameters have been used to diagnose noninvasive fetal anemia. On the basis of robust data, the MCA PSV is the best ultrasonographic parameter used in the management of fetuses at risk for anemia due to different causes. It is also superior to amniocentesis for the diagnosis of fetal anemia in cases of red cell alloimmunization.

CONCLUSIONS

Middle cerebral artery peak systolic velocity is effective for diagnosis of noninvasive moderate and severe fetal anemia. This parameter should not yet be considered the global standard of care for diagnosis of fetal anemia because incorrect use by an inexperienced operator may cause more harm than good; however, if there is a reasonably close medical center with sonographers or sonologists trained to assess the MCA PSV, patients at risk for fetal anemia should be referred to this center.