Comparison of different reference values of fetal blood flow velocity in the middle cerebral artery for predicting fetal anemia

Confirmatory Middle Cerebral Artery Doppler Testing in Alloimmunized Patients with Suspected Fetal Anemia

OBJECTIVE

 This article aimed to evaluate pregnancy outcomes when a plan to perform fetal blood sampling (FBS) or delivery was based solely on the first abnormal middle cerebral artery peak velocity (MCA-PV) measurement compared with making a plan after a confirmatory test on a subsequent day.

STUDY DESIGN

 We performed a descriptive study of pregnancy outcomes including all patients in a single healthcare system with maternal red cell alloimmunization undergoing ultrasound between 2005 and 2017 who had at least one MCA-PV>1.5 multiples of the median (MoM). We excluded patients with any sign of hydrops prior to the index visit or abnormal MCA-PV at>35 weeks. The first exam with a MCA-PV>1.5 MoM was deemed the index visit.

RESULTS

 Fifty patients were identified. Twenty-one patients underwent intervention (FBS or delivery) based on the first abnormal MCA-PV. Of those, 9 had moderate or severe anemia (positive predictive value [PPV]: 43%), while 12 had mild or no anemia. The other 29 patients underwent a confirmatory MCA test between 2 and 8 days later. Of these, 13 patients had an abnormal confirmatory test and 11 of these underwent FBS and 7 had moderate or severe anemia (PPV: 54%). Sixteen patients undergoing confirmatory MCA Doppler had a normal test on repeat and did not undergo FBS. Of those, none developed moderate or severe anemia.

CONCLUSION

 A substantial number of patients (55%) had normal MCA-PV testing on repeat, allowing avoidance of invasive testing. Deferring FBS until the abnormal MCA-PV was confirmed was not associated with undetected moderate or severe anemia.

KEY POINTS

· False-positive results from MCA-PV Doppler prediction of fetal anemia are common.. · Repeat noninvasive testing is normal in many patients with suspected fetal anemia.. · Invasive fetal testing can often be safely avoided by performing a confirmatory Doppler exam ination..

Elevated fetal middle cerebral artery peak systolic velocity in diabetes type 1 patient: a case report

Objectives

Doppler measurement of fetal middle cerebral artery peak systolic velocity (MCA-PSV) is used to screen fetuses at risk of developing fetal anemia. This screening tool has demonstrated to be accurate to estimate the likelihood of fetal anemia and it has been used in the management of fetuses at this risk. It is rare to find in the literature cases of increased MCA-PSV in the absence of fetal anemia. We present the case of an elevated MCA-PSV in the absence of common causes of fetal anemia.

Case presentation

A 30-year-old woman at 21 weeks of gestation was referred to our unit with a left fetal renal agenesis and single umbilical artery diagnosis. The patient had a poorly controlled type 1 Diabetes with a booking HbA1C of 9.1%. At 31 weeks of gestation, MCA-PSV was raised (>1.5 multiples of the median) in the absence of any cause of fetal anemia and discrepancy of ventricular size with normal fetal heart function were seen. In a subsequent scan, thick interventricular septum was seen and hypertrophic cardiomyopathy (HC) was suggested. Follow-up ultrasonography showed a persistent MCA-PSV in a large for gestation age (LGA) fetus with HC. Due to the prenatal diagnosis of persistent elevated MCA-PSV in LGA fetus with diagnoses of HC in a poorly controlled type 1 diabetic patient labor was induced after fetal lung maturation. Biventricular hypertrophic cardiomyopathy was detected after birth.

Conclusions

HC may be an explanation for increased MCA-PSV without fetal anemia.

Unexpected middle cerebral artery peak systolic velocity values in the normal fetal population. Are they a matter of concern?

Objective: The aim of this study was to investigate in the fetus the relationship between unexpected high middle cerebral artery peak systolic velocity (middle cerebral artery (MCA) peak systolic velocity (PSV)) values and hemoglobin (Hgb) levels in normal pregnancies without conditions leading to fetal anemia.Material and methods: This was a prospective study of 922 singleton low-risk pregnant women attending the maternity of La Fe Hospital between 35 and 41 weeks. Multiple pregnancies and pregnancies with growth restriction, smallness, macrosomia or conditions leading to fetal anemia were excluded. During each examination, a biometry and a Doppler examination of the umbilical artery pulsatility index (umbilical artery (UA) pulsatility index (PI)), MCA PI and MCA PSV were performed. MCA PSV was converted into multiples of median (MoM), and birth weight (BW) into centiles adjusting for gender. All pregnancies delivered in a 2-week interval since examination. In order to explain Hgb levels at birth, a correlation between MCA PSV MoM and Hgb was performed and Hgb levels of fetuses with normal MCA PSV and abnormal MCA PSV were compared, using 1.3 MoM as cut-off for mild anemia. Finally, a multivariate linear regression analysis was performed including MCA PSV MoM and several Doppler and clinical parameters.Results: The univariate analysis showed no correlation between the MCA PSV MoM and the umbilical artery Hgb (r² = 0.026, p = .1237) while a weak correlation was found with the umbilical vein Hgb (r² = 0.0053, p = .027). Also, fetuses with values of MCA PSV MoM <1.3 MoM did not differ in terms of artery and vein Hgb with those presenting values >1.3 MoM (p = .99 and p = .61, respectively). Finally, both prediction models explaining arterial and venous Hgb presented very weak predictive accuracies (R Squared: 0.0965 and R Squared: 0.106) indicating a low possibility to diagnose fetal anemia in otherwise normal fetuses based on clinical and sonographic data.Conclusion: In normal pregnancies that are not suffering from conditions leading to fetal anemia, unexpected high MCA PSV values do not necessarily reflect the presence of this condition. Active management in this circumstance might result in unjustified higher rates of labor induction and operative delivery.

Noninvasive approach for the management of hemolytic disease of the fetus

Hemolytic disease of the fetus and newborn (HDFN) is due to maternal alloantibodies directed against paternally inherited antigens on fetal red cells, and it is still a problem in affected pregnancies despite the routine use of anti-D immunoglobulin during pregnancy and shortly after delivery. The current noninvasive management of HDFN starts with the determination of fetal RhD genotype by use of cell-free fetal DNA in maternal plasma. When the fetus is antigen positive, the follow-up is performed by Doppler ultrasonography for the detection of moderate or severe anemia on the basis of an increase peak velocity of systolic blood in the middle cerebral artery. Finally, if anemia is suspected, an invasive approach is required in order to perform an intrauterine blood transfusion, which should only be attempted when the fetus needs transfusion. This approach reduces the iatrogenic conversion of mild-to-severe disease, which occurred as a result of the previous invasive management, and prevents unnecessary administration of human-derived blood products. These changes represent one of the genuine successes of fetal therapy.

Determinants of the middle cerebral artery peak systolic velocity in the human fetus

OBJECTIVE

The purpose of this study was to identify physiologic determinants of the peak systolic blood flow velocity (PSV) of the middle cerebral artery (MCA) in the human fetus.

STUDY DESIGN

MCA PSV was measured with pulsed wave Doppler ultrasound in human fetuses who underwent cordocentesis. Hemoglobin, hematocrit, and blood gas values were analyzed from umbilical venous blood, and the data were normalized for gestational age. Total oxygen content of fetal venous blood was calculated from oxygen saturation, hemoglobin value, and pO2. Correlation and logistic regression analyses were performed to identify primary physiologic determinants of MCA PSV.

RESULTS

In 136 fetuses who underwent cordocentesis (predominantly for alloimmune disease), hematocrit, hemoglobin, and blood oxygen content correlated significantly with the MCA PSV (P < .01). Logistic regression modeling demonstrated that fetal hemoglobin content (odds ratio, 7.1; 95% CI, 3.71-13.7) and pCO2, but not pO2 or fetal blood oxygen content, accounted for increases in MCA PSV.

CONCLUSION

Under physiologic circumstances, fetal hemoglobin, and not fetal oxygenation, primarily determines the middle cerebral artery peak systolic velocity.

Prediction of severe fetal anemia in red blood cell alloimmunization after previous intrauterine transfusions

OBJECTIVE

This study was undertaken to determine the detection of fetal anemia and false-positive rates by fetal middle cerebral artery peak systolic velocity (MCA-PSV) and the estimated daily decrease of hemoglobin (Hb) in red blood cell alloimmunized pregnancies that had previous fetal transfusions.

STUDY DESIGN

We examined the relation between MCA-PSV measured before cordocentesis, and fetal Hb at the time of the second (n = 42) and third (n = 31) intrauterine blood transfusions. In addition, the daily Hb drop between the transfusions was calculated.

RESULTS

The MCA-PSV provided significant prediction of severe anemia (Hb deficit > or = 6 g/dL) for the second but not for the third transfusion. Detection of 95% of severely anemic fetuses was achieved with a false-positive rate of 37% for the second transfusion and 90% for the third, compared with 14% in our previous study for the first transfusion. In patients who had received 2 previous transfusions, the only significant predictor of fetal anemia was the estimation of the Hb from the measured posttransfusion Hb after the second transfusion and the assumption that the rate of decrease in fetal Hb is 0.3 g/dL per day.

CONCLUSION

Prediction of severe fetal anemia after one transfusion is less accurate than in nontransfused fetuses. The MCA-PSV is not useful in predicting severe anemia in fetuses that already had 2 previous transfusions.

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.