Pulsed Doppler flow-velocity waveforms in the prediction of fetal hematocrit of the severely isoimmunized pregnancy

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.

Intervalos de referência do pico de velocidade sistólica da artéria cerebral média fetal na população brasileira

OBJETIVO: Determinar uma curva de referência baseada em múltiplos da mediana para o pico de velocidade sistólica da artéria cerebral média fetal. MATERIAIS E MÉTODOS: Realizou-se estudo de corte transversal com 143 gestantes normais entre 23 e 35 semanas. Realizou-se varredura bidimensional em corte axial do crânio fetal, incluindo os tálamos e o septo pelúcido, e em seguida acionou-se o modo color Doppler, visualizando-se a artéria cerebral média. O Doppler pulsátil foi disposto próximo à origem deste vaso, utilizando-se ângulo de insonação de menos de 20°. Para avaliar a correlação do pico de velocidade sistólica da artéria cerebral média com a idade gestacional, utilizou-se o coeficiente de correlação de Person (r). Por meio de modelos de regressão, construiu-se uma tabela de múltiplos da mediana para o pico de velocidade sistólica da artéria cerebral média em cada idade gestacional avaliada, e adicionalmente determinaram-se valores de referência para essa variável. RESULTADOS: Observou-se forte correlação entre o pico de velocidade sistólica da artéria cerebral média e a idade gestacional (r = 0,70; p = 0,001). Determinaram-se valores do pico de velocidade sistólica da artéria cerebral média para os seguintes múltiplos da mediana: 1,0; 1,29; 1,5; 1,55. Determinaram-se os percentis 2,5 e 97,5 para o pico de velocidade sistólica da artéria cerebral média, variando de 24,33 cm²/s a 78,36 cm²/s. CONCLUSÃO: Um nomograma do pico de velocidade sistólica da artéria cerebral média fetal foi determinado.

Nomogram of fetal middle cerebral artery peak systolic velocity at 23-35 weeks of gestation in a Brazilian population: pilot study

OBJECTIVE

To establish normative data for the peak systolic velocity of the middle cerebral artery (MCA-PSV) of fetuses in the second half of pregnancy using multiples of the median and percentile reference range.

METHODS

A cross-sectional study was performed in 90 healthy fetuses at between 23 and 35 weeks of gestation. A bi-dimensional axial scan of the brain, including the thalami and cavitas septi pellucidi was obtained. The circle of Willis was visualized using color flow mapping. Pulsed-wave Doppler velocimetry of the MCA was performed close to the artery's origin, with a beam-vessel angle below 20 degrees . A table with the multiples of the median (MoM) of the MCA-PSV for each gestational age was generated and Pearson's correlation coefficient (r) was calculated. Regression modeling across gestational age was performed to obtain the reference values.

RESULTS

There was a strong correlation between the MCA-PVS and gestational age (r = 0.70; p < 0.001). Values for the MCA-PSV for the following MoM were calculated: 1.0, 1.29, 1.50, and 1.55. The MCA-PSV 2.5(th) and 97.5(th) centiles ranged from 24.33 cm(2)/s to 78.36 cm(2)/s, respectively, between weeks 23 and 35.

CONCLUSIONS

A nomogram for the fetal MCA-PSV during the second half of pregnancy was generated.

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.

Perinatal mortality in Rh alloimmunized patients

OBJECTIVE

Evaluate and compare the perinatal mortality of Rh-negative pregnancies managed at São Paulo Federal University during a 9-year period, using either amniocentesis or middle cerebral artery peak systolic velocity.

METHOD

Descriptive observational study involving 291 consecutive Rh-negative pregnancies managed between January 1995 and January 2004. The perinatal mortality of 99 alloimmunized patients was compared with 192 Rh-negative unimmunized patients (control group). The perinatal mortality of patients managed with amniocenteses was compared to those managed with Doppler studies.

RESULTS

There were 74 patients managed with amniocenteses and 25 managed with Doppler studies. Perinatal mortality was significantly higher in the 99 Rh-negative isoimmunized patients than in the 192 unimmunized patients (12.1% versus 1%, p=0.0001) and did not differ according to the management protocol used (amniocentesis 13.5% versus cerebral Doppler 8.0%, p=0.725). Mean gestational age and mean weight at birth in pregnancies managed with amniocenteses (35.7 weeks and 2586 g) did not differ significantly from those managed with Doppler (36.3 weeks and 2647 g).

CONCLUSIONS

Perinatal mortality in Rh-negative alloimmunized patients remains high and does not differ whether pregnancies are managed through amniocentesis or cerebral Doppler evaluation.

Rh alloimmunization: Doppler or amniotic fluid analysis in the prediction of fetal anemia?

OBJECTIVE

Compare the results of amniocentesis and those of middle cerebral artery peak systolic velocity to detect anemic fetuses in Rh alloimmunized pregnancies.

METHOD

Descriptive observational study involving 99 consecutive Rh-negative pregnancies: 74 alloimmunized patients submitted to amniotic fluid spectrophotometry (group 1) and 25 alloimmunized cases managed with Doppler ultrasonography (group 2). Variables analyzed were the following: need for neonatal transfusion and neonatal hematocrit.

RESULT

Neonatal hematocrit was significantly lower and the need for neonatal transfusion was significantly higher in cases managed with spectrophotometry compared to those managed with Doppler.

CONCLUSION

Infants managed with Doppler velocimetry had higher hematocrit and less need for neonatal transfusion, suggesting that this non-invasive method of monitoring fetal anemia may best preserve the neonate.

Alterações ultra-sonográficas na gravidez Rh negativo sensibilizada avaliada pela espectrofotometria do líquido amniótico e pela dopplervelocimetria da artéria cerebral média

OBJETIVO: Avaliar e confrontar a presença de alterações ultra-sonográficas nas gestações Rh negativo sensibilizadas, quando a anemia fetal foi determinada ou pela espectrofotometria do líquido amniótico, ou pela dopplervelocimetria da artéria cerebral média. MATERIAIS E MÉTODOS: Observacional descritivo com grupo de comparação. Nosso grupo de estudo foi constituído por 99 pacientes, avaliadas no período de janeiro de 1995 a janeiro de 2004. Foram analisados e comparados dois grupos: 74 gestantes sensibilizadas pelo fator Rh cuja anemia fetal foi acompanhada pela espectrofotometria (grupo SE) e 25 gestantes sensibilizadas pelo fator Rh cuja anemia fetal foi acompanhada pela dopplervelocimetria (grupo SD). Avaliamos a presença ou não de alterações ultra-sonográficas no acompanhamento pré-natal e confrontamos os dois grupos de estudo. RESULTADOS: No grupo cuja anemia fetal foi acompanhada através da espectrofotometria (grupo SE), apuramos modificações placentárias, principalmente o aumento da espessura e sua alteração textural, mais assiduamente que as encontradiças no grupo de gestantes sensibilizadas, em que a anemia foi determinada através da dopplervelocimetria (grupo SD) (64% X 32%, p = 6,294). CONCLUSÃO: As alterações ultra-sonográficas foram detectadas em dobro quando a anemia foi avaliada pela espectrofotometria em comparação com o grupo seguido pela dopplervelocimetria.

Pregnancy outcome for Rh-alloimmunized women

OBJECTIVE

To compare perinatal results of Rh-alloimmunized pregnancies managed with spectrophotometric amniotic fluid analysis or fetal middle cerebral artery Doppler ultrasonographic velocimetry.

METHOD

A descriptive observational study involving 291 consecutive Rh-negative pregnancies. Group 1 consisted of 74 isoimmunized women managed with amniotic fluid spectrophotometry; group 2 of 25 isoimmunized women managed with Doppler ultrasonography; and group 3 of 192 nonimmunized Rh-negative women. The variables analyzed were need for intrauterine or neonatal transfusion, mode and time of delivery, birth weight, neonatal hematocrit, and perinatal mortality.

RESULTS

Need for intrauterine transfusion, birth weight, prematurity, rate of cesarean section, and perinatal mortality were similar in groups 1 and 2. Neonatal hematocrit was significantly lower and the need for neonatal transfusion was significantly higher when spectrophotometry rather than Doppler ultrasonographic velocimetry was used.

CONCLUSION

Fetuses managed with Doppler ultrasonographic velocimetry had a higher hematocrit at birth and a lesser need for neonatal transfusion, suggesting that this noninvasive method of monitoring fetal anemia is a better choice.

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.

Diagnosis, surveillance, and treatment of the anemic fetus using middle cerebral artery peak systolic velocity measurement

The in utero course of the anemic fetus has improved dramatically, owing to early diagnosis and cordocentesis transfusion. In utero invasive procedures such as amnio- and cordocentesis have become important modalities in the evaluation and treatment of anemic fetuses. However, they carry risks for both the mother and fetus. A valid and sensitive noninvasive means of following the anemic fetus is the evaluation of changes in the middle cerebral artery peak systolic flow velocity (MCA-PSV). This is a sensitive tool for both the evaluation of fetal anemia and response to treatment. Intracerebral vessels respond earliest to the fetal anemic state, and are readily accessible for ultrasound examination. We describe the methodology and evolving clinical applications of MCA-PSV measurement in the fetus, through an overview of the literature describing the development and application of MCA-PSV measurement in fetuses at risk of fetal anemia of various immune and nonimmune etiologies, illustrated by index cases from our center. MCA-PSV measurement is essential in the diagnosis, evaluation, and management of cases of fetal anemia. The use of this modality lessens the need for invasive procedures. The method is readily accessible and should be integrated into the repertoire of all obstetric ultrasound centers.

Fetal Doppler velocimetry

The introduction of new techniques for evaluating fetal status, particularly fetuses at theoretical risk for hypoxic ischemic encephalopathy, requires the most rigorous evaluation before widespread clinical deployment. The considerations extend beyond clinical value to the significant medicolegal implications of a failure to predict or ascertain compromise. The attitudes to clinical Doppler velocimetry have been shaped to a large extent by these practical concerns and the initial skepticism, which is a necessary component of scientific rigor. Available data strongly indicate, however, that in competent hands umbilical artery Doppler im-proves the clinical management of IUGR pregnancies. Failure to use Doppler may have the undesirable effect of increasing the risk of adverse outcome in the growth-restricted fetus. There is also strong evidence of benefit in the management of the Rh isoimmunization. Although numerous other clinical applications are on the horizon, much more information is needed to determine objectively the benefits and risks of these newer applications.

A comparison between middle cerebral artery peak systolic velocity and amniotic fluid optical density at 450 nm in the prediction of fetal anemia

OBJECTIVE

The purpose of this study was to compare fetal middle cerebral artery peak systolic velocity with amniotic fluid delta optical density at 450 nm in the prediction of fetal anemia.

STUDY DESIGN

A prospective study that involved 28 singleton pregnancies that were at-risk for fetal anemia was carried out in a tertiary teaching hospital. Middle cerebral artery peak systolic velocity was measured immediately before the determination of deltaoptical density at 450 nm and fetal hemoglobin concentration. Sensitivities and predictive values for fetal anemia were examined.

RESULTS

Fetal hemoglobin concentrations correlated significantly with middle cerebral artery peak systolic velocity (correlation coefficient, -0.77; P <.0001) and deltaoptical density at 450 nm zones (correlation coefficient, -0.56; P =.0025). Middle cerebral artery peak systolic velocity was >1.5 multiples of the median in 15 of 28 cases (54%); for this cutoff value, the sensitivity and positive-predictive values for a hemoglobin deficit of >-3SD were 75% and 60% and for a hemoglobin deficit of >-5SD were 100% and 47%, respectively. The corresponding values for deltaoptical density at 450-nm zone III (6/28 cases, 21%) were 0% (hemoglobin deficit, <-3SD) and 86% and 100% (hemoglobin deficit, <-5SD).

CONCLUSION

Middle cerebral artery peak systolic velocity and amniotic fluid optical density at 450 nm are both useful in the prediction of fetal anemia. However, Doppler examination has the advantage of being a noninvasive method that can help reduce the number of invasive procedures in pregnancies that are at-risk for fetal anemia.

Prediction of fetal anaemia

The perinatal outcome of the anaemic fetus has dramatically improved over the last 20 years, as a result of early recognition of the problem and treatment by intrauterine transfusion. Traditionally assessment of the anaemic fetus relied on obstetric history and maternal antibody titre, which proved to be inadequate tests to accurately predict fetal condition. More recently, invasive testing with techniques such as amniocentesis and cordocentesis have allowed a more accurate evaluation of the degree of anaemia, while at the same time enabling transfusion to take place. Such techniques are not without danger, with perinatal loss and fetomaternal haemorrhage being significant risks. The clinical community has therefore sought to find accurate, non-invasive methods for assessing the degree of fetal anaemia, thereby reducing the number of unnecessary invasive procedures, while at the same time providing more precise data on the quantity and timing of the transfusion. Recent publications focusing on the diagnosis and management (including plasmapheresis, immunoglobulins and intrauterine transfusion) of fetal anaemia will be discussed.

Invasive versus non-invasive testing in red-cell alloimmunized pregnancies

Amniocentesis for amniotic fluid bilirubin levels is the most widely used test to predict the severity of fetal disease in red-cell alloimmunization. Many textbooks and guidelines recommend serial amniocentesis to monitor these pregnancies. However, the reliability of amniotic fluid bilirubin measurements has been questioned. Two strategies have been proposed by investigators. Some advocate liberal or primary use of fetal blood sampling, while others promote the use of non-invasive ultrasonography and Doppler. The purpose of this literature review is to examine the usefulness of amniocentesis, ultrasonography and Doppler to predict the degree of fetal hemolytic anemia. The evidence suggests that amniotic fluid bilirubin measurements are of limited value in the second trimester. Furthermore, critical appraisal of the very few prospective studies is hampered by limitations in design or insufficient data given by the authors. Many ultrasound and Doppler parameters have been proposed as useful indicators of fetal anemia. The most promising of these methods are Doppler assessment of umbilical venous and middle cerebral artery flow velocities. We speculate that the accuracy of these non-invasive tests may be good enough to incorporate them in management protocols, possibly replacing amniocentesis. Well-designed prospective studies are needed to prove this hypothesis.

Sonographic methods to detect fetal anemia in red blood cell alloimmunization

Published reports, case studies, and articles from the English language regarding ultrasonographic detection of fetal anemia in red blood cell alloimmunization were obtained from a MEDLINE search from 1966 to November 1999 using the keywords Rh disease, hemolytic disease of the newborn, ultrasound, and Doppler flow studies and combinations thereof. All articles were cross-referenced. Ultrasound techniques including early findings associated with immune hydrops fetalis, multiple morphologic ultrasound markers, and Doppler flow studies that have been used to detect fetal anemia are reviewed and critically evaluated. Noninvasive sonographic techniques may reduce the number of invasive procedures that traditionally are used to follow fetuses at risk for anemia and decrease the associated risks from these procedures.

Noninvasive diagnosis by Doppler ultrasonography of fetal anemia due to maternal red-cell alloimmunization. Collaborative Group for Doppler Assessment of the Blood Velocity in Anemic Fetuses

BACKGROUND

Invasive techniques such as amniocentesis and cordocentesis are used for diagnosis and treatment in fetuses at risk for anemia due to maternal red-cell alloimmunization. The purpose of our study was to determine the value of noninvasive measurements of the velocity of blood flow in the fetal middle cerebral artery for the diagnosis of fetal anemia.

METHODS

We measured the hemoglobin concentration in blood obtained by cordocentesis and also the peak velocity of systolic blood flow in the middle cerebral artery in 111 fetuses at risk for anemia due to maternal red-cell alloimmunization. Peak systolic velocity was measured by Doppler velocimetry. To identify the fetuses with anemia, the hemoglobin values of those at risk were compared with the values in 265 normal fetuses.

RESULTS

Fetal hemoglobin concentrations increased with increasing gestational age in the 265 normal fetuses. Among the 111 fetuses at risk for anemia, 41 fetuses did not have anemia; 35 had mild anemia; 4 had moderate anemia; and 31, including 12 with hydrops, had severe anemia. The sensitivity of an increased peak velocity of systolic blood flow in the middle cerebral artery for the prediction of moderate or severe anemia was 100 percent either in the presence or in the absence of hydrops (95 percent confidence interval, 86 to 100 percent for the 23 fetuses without hydrops), with a false positive rate of 12 percent.

CONCLUSIONS

In fetuses without hydrops that are at risk because of maternal red-cell alloimmunization, moderate and severe anemia can be detected noninvasively by Doppler ultrasonography on the basis of an increase in the peak velocity of systolic blood flow in the middle cerebral artery.

Acceleration time in normal fetal umbilical artery at term and its relationship to the cord blood hematocrit

The purpose of this study was to test the hypothesis that the acceleration time (AT) of the fetal umbilical artery remains constant at term for normal pregnancies. In addition, we also examined whether the AT has any correlation with umbilical cord blood hematocrit (Hct). In total, 539 normal-term fetuses with menstrual ages (MA) ranging from 37 weeks to 42 weeks were enrolled in a cross-sectional design. The AT of the fetal umbilical artery was measured prior to delivery using a high-resolution, real-time Doppler scanner. All were delivered within 2 days of the ultrasound examination. At parturition, blood from the umbilical vein was collected and the red cell indices, including the Hct, were determined. The results indicated that the mean values of AT of the umbilical artery remained constant during normal-term pregnancies from 37 weeks to 42 weeks, menstrual age (mean: 0.104 sec, SE: 0.001 sec, n = 539). Although the AT was thought to be affected by the Hct, the AT had no correlation with umbilical venous Hct (n = 539, r = 0.002, p > 0.05). This constant value of the AT may be used as a reference for fetal physiology and perinatal medicine.

The use of ultrasonography and Doppler in the prediction of fetal haemolytic anaemia: a multivariate analysis

OBJECTIVE

To assess the value of ultrasonography and Doppler to predict the severity of fetal haemolytic anaemia.

DESIGN

Ultrasonographic measurements of the fetal liver, spleen, umbilical vein and placenta, and Doppler measurements of umbilical venous and fetal aorta flow velocities were performed before the first intrauterine blood transfusion. Multivariate regression models for the prediction of the fetal haemoglobin level were derived from the measurements.

SETTING

National referral centre for management of alloimmunised pregnancies.

SUBJECTS

Forty fetuses in 39 severe red cell alloimmunised pregnancies.

RESULTS

A logistic regression model, incorporating the two Doppler parameters only, predicted the presence or absence of severe anaemia in nonhydropic fetuses with an accuracy of 90%. Positive predictive value was 89% and negative predictive value was 100%.

CONCLUSION

In severe red cell alloimmunised pregnancies, Doppler blood flow velocity studies can be used to predict the severity of fetal anaemia. This may lead to a reduction of invasive diagnostic tests, to more accurate timing of intrauterine transfusions, and thus to a higher survival rate.

Umbilical artery Doppler flow-velocity waveforms in Rhesus-isoimmunized fetuses before and after fetal blood sampling or transfusion

Pulsed-Doppler examinations of blood-flow velocities in the umbilical artery were carried out before and after 15 diagnostic cordocenteses and 34 fetal blood transfusions into the umbilical vein. There were decreases in the systolic/diastolic ratio (A/B) (p < 0.01), the pulsatility index (PI) (p < 0.05), and the resistance index (RI) (p < 0.01) after cordocentesis but not after fetal blood transfusion. There were no correlations between the initial hematocrit and the umbilical artery Doppler indices in the sample nor in the fetal blood sampling group. In the fetal blood transfusion group, on the other hand, there was a negative correlation between the initial hematocrit and A/B (r = -0.44; p < 0.01) and the RI (r = -0.35; p < 0.05). The umbilical artery Doppler flow-velocity indices did not predict the fetal hematocrit.

Doppler velocimetry in pregnancy

Since the late 1970s, Doppler velocimetry has been investigated extensively for use in obstetrics. Initially, this technique showed promise for the management of certain complications of pregnancy; this promise has yet to be fulfilled. Doppler velocimetry of either the uterine or umbilical vessels, which showed some merit in selecting growth-retarded fetuses at particular risk, has neither become a screening tool for intrauterine growth retardation nor proven clinically successful in improving fetal outcome. Likewise, its use for other complications of pregnancy (eg, postdate pregnancy, twin pregnancy, and diabetes) has not led to improved pregnancy outcome. More recently this technique has been used to study other vascular beds. Changes in the Doppler characteristics of these vascular beds may demonstrate the fetal response to its environment. These investigations provide the potential for a better understanding of fetal physiology; however, it has yet to be shown by prospective evaluation that their application results in improved pregnancy outcome. This review defines the uses and limitations of Doppler ultrasound in current obstetric practice.

Alloimmune conditions and pregnancy

Transfer of fetal red blood cells and platelets to the maternal circulation can stimulate an immune response with production of immunoglobulin that can cross the placenta. Similarly, passage of maternal stem cells to an immunologically incompetent fetus can theoretically produce graft-versus-host disease. disease. Maternal sensitization to red blood cell antigens such as D and Kell can result in anaemia, hydrops, and death in an incompatible fetus. Current assessment of these pregnancies involves serial analysis of amniotic fluid bilirubin concentration, with umbilical cord blood sampling reserved for special circumstances; neither ultrasound or Doppler blood flow analysis are accurate in the prediction of fetal haematocrit. Intravascular transfusion is the treatment of choice for hydropic fetuses. Perinatal survival in non-hydropic fetuses is similar with either intravascular or intraperitoneal transfusion, and the choice of procedures is individualized. Isoimmune fetal thrombocytopenia is usually the result of maternal sensitization to the PlA1 antigen. There is significant risk of intracranial haemorrhage, both antepartum and during labour and delivery. Umbilical cord blood sampling at term can determine fetal platelet count and the need for platelet transfusion, and can aid in deciding the appropriate route of delivery.

Management of immune haemolytic disease in the fetus

Although Rh alloimmunization has been successfully reduced in frequency and severity since the implementation of Rh immune globulin, cases still occur. The management of affected pregnancies requires the efforts of a team which includes obstetrics/fetal medicine, the blood transfusion service, haematological support, nursing assistance and neonatology. The aim of antenatal management is to predict whether or not the fetus is severely affected, to correct the fetal anaemia and to deliver the baby at the optimal time. The management has improved markedly with the introduction of high-resolution real-time ultrasound, fetal blood sampling, intravascular fetal blood transfusion and/or intraperitoneal transfusion and meticulous fetal surveillance. With appropriate and timely management in severely alloimmunized patient, the survival rate of affected fetuses in some centres is now about 90%. There is still a need for research into new methods of treatment such as high dose intravenous immunoglobulin, which might non-invasively diminish fetal red cell destruction. Due to the reduced frequency of severe disease, regionalized treatment centres are essential in order to maximize the experience and efficiency of the management teams.