Ultrasonographic surveillance in red blood cell alloimmunization

Morphometric study of the diaphragmatic surface of the liver in the human fetus

This study aimed to examine age-specific reference intervals and growth dynamics of the best fit for liver dimensions on the diaphragmatic surface of the fetal liver. The research material consisted of 69 human fetuses of both sexes (32♂, 37♀) aged 18–30 weeks. Using methods of anatomical dissection, digital image analysis and statistics, a total of 10 measurements and 2 calculations were performed. No statistical significant differences between sexes were found (p>0.05). The parameters studied displayed growth models that followed natural logarithmic functions. The mean value of the transverse–to–vertical diameter ratio of the liver throughout the analyzed period was 0.71±0.11. The isthmic ratio decreased significantly from 0.81±0.12 in the 18–19th week to 0.62±0.06 in the 26–27th week, and then increased to 0.68±0.11 in the 28–30th week of fetal life (p<0.01). The morphometric parameters of the diaphragmatic surface of the liver present age-specific reference data. No sex differences are found. The transverse–to–vertical diameter ratio supports a proportionate growth of the fetal liver. Quantitative anatomy of the growing liver may be of relevance in both the ultrasound monitoring of the fetal development and the early detection of liver anomalies.

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.

Three-dimensional growth dynamics of the liver in the human fetus

Purpose

The fetal liver is indubitably the earliest and the most severely affected organ by abnormal fetal growth. The size of the fetal liver assessed by three-dimensional ultrasonography is indispensable in determining the status of fetal growth, nutrition and maturity, and in the early recognition and monitoring fetal micro- and macrosomias. The aim of the present study was to measure the human fetal liver length, transverse and sagittal diameters to establish their age-specific reference intervals, the 3rd, 10th, 50th, 90th, and 97th smoothed centile curves, and the relative growth of the liver calculated for the 50th centile.

Materials and methods

Using anatomical, digital (NIS-Elements AR 3.0, Nikon) and statistical methods (one-way ANOVA test for paired data and post hoc RIR Tukey test, Shapiro–Wilk test, Fisher’s test, Student’s t test, the Altman-Chitty method), length, transverse and sagittal diameters of the liver for the 3rd, 10th, 50th, 90th, and 97th centiles were assessed in 69 human fetuses of both sexes (32 males and 37 females) aged 18–30 weeks, derived from spontaneous abortions or stillbirths.

Results

No male–female differences (P > 0.05) concerning the three parameters studied were found. During the study period, the fetal liver increased tri-dimensionally: in length from 19.51 ± 1.02 to 39.65 ± 7.05 mm, in transverse diameter from 29.44 ± 3.73 to 53.13 ± 5.31 mm, and in sagittal diameter from 22.97 ± 3.79 to 43.22 ± 5.49 mm. The natural logarithmic models were found to fit the data with gestational age (P < 0.001) in the following five cutoff points: 3rd, 10th, 50th, 90th and 97th centiles. The values of liver parameters in relation to gestational age in weeks were calculated by the following logarithmic regressions: y = −82.778 + 35.752 × ln(age) ± Z × (−2.778 + 0.308 × age) for liver length, y = −123.06 + 52.668 × ln(age) ± Z × (3.156 + 0.049 × age) for liver transverse diameter, and y = −108.94 + 46.052 × ln(age) ± Z × (−0.541 + 0.188 × age) for liver sagittal diameter. For the 50th centile, at the range of 18–30 weeks, the growth rates per week were gradually decreasing from 1.93 to 1.21 mm for length, from 2.85 to 1.79 mm for transverse diameter, and from 2.49 to 1.56 mm for sagittal diameter of the liver (P < 0.05). During the study period both the length-to-transverse diameter ratio and the sagittal-to-transverse diameter ratio of the liver changed little, attaining the values of 0.71 ± 0.11 and 0.87 ± 0.12, respectively.

Conclusions

The fetal liver does not reveal sex differences in its length, transverse and sagittal diameters. The fetal liver length, transverse and sagittal diameters grow logarithmically. The regression equations for the estimation of the mean and standard deviation of liver length, transverse and sagittal diameters allow for calculating any desired centiles according to gestational age. The three-dimensional evolution of the fetal liver follows proportionately. The age-specific reference intervals for evolving liver length, transverse and sagittal diameters constitute the normative values of potential relevance in monitoring normal fetal development and screening for disturbances in fetal growth.

Normal length of the fetal liver from 14 to 40 weeks of gestational age

OBJECTIVE

To create a normal reference table of fetal liver length in normal fetuses

METHODS

A prospective, cross-sectional study was conducted on normal pregnancies with accurate gestational age (GA) from 14 to 40 weeks of gestation. All fetuses were measured for fetal liver length from the top of the right hemidiaphragm to tip of the right liver lobe on coronal image of the fetal abdomen, using high-resolution real-time ultrasound with a 2- to 4-MHz convex transducer.

RESULTS

A total of 685 normal pregnant women between 14 and 40 weeks of gestation were recruited. Forty-five were excluded due to poor image quality and fetal abnormalities. The remaining 640 were available for analysis. The linear regression model was best fitted to estimate the 5th, 50th, and 95th percentile range of liver length at each gestational week. Fetal liver length was gradually increased with GA with fitted equation as follows: Liver length (mm) = 1.61 (GA, week) - 6.75 (r(2) = 0.94, p < 0.001).

CONCLUSION

A normal reference range of fetal liver length for each GA between 14 and 40 weeks was constructed. This may be a useful tool in assessment for some fetal pathologic conditions, especially when fetal anemia is suspected.

Red Blood Cell Alloimmunization in Pregnancy

Red blood cell (RBC) alloimmunization in pregnancy continues to occur despite the widespread use of both antenatal and postpartum Rhesus immune globulin (RhIG), due mainly to inadvertent omissions in administration as well as antenatal sensitization prior to RhIG given at 28 weeks' gestation. Additional instances are attributable to the lack of immune globulins to other RBC antigens. Evaluation of the alloimmunized pregnancy begins with the maternal titer. Once a critical value [32 for anti-Rh(D) and other irregular antibodies; 8 for anti-K and -k] is reached, fetal surveillance using serial Doppler ultrasound measurements of the peak velocity in the fetal middle cerebral artery (MCA) is standard. In the case of a heterozygous paternal phenotype, amniocentesis can be performed to detect the antigen-negative fetus that requires no further evaluation. MCA velocities greater than 1.5 multiples of the median necessitate cordocentesis, and if fetal anemia is detected, intrauterine transfusion therapy is initiated. A perinatal survival of greater than 85% with normal neurologic outcome is now expected. Future therapies will target specific immune manipulations in the pregnant patient.

Condition-specific antepartum fetal testing

OBJECTIVE

The purpose of this study was to determine the best available antepartum fetal testing methods according to the underlying pathophysiologic condition.

STUDY DESIGN

We reviewed the current literature and our clinical experience with respect to condition-specific antepartum fetal testing.

RESULTS

The efficacy of most antepartum tests that we use today is not supported by randomized controlled clinical trials, but from observational nonrandomized studies and expert opinion (evidence levels II or III).

CONCLUSION

Based on the available evidence, the accuracy of a test depends on the underlying pathophysiologic condition. To improve accuracy, we must use condition-specific fetal testing.

The effect of fetal behavioral states on middle cerebral artery peak systolic velocity

OBJECTIVE

This study was undertaken to determine whether is there a difference in the middle cerebral artery peak systolic velocity (MCA PSV) between active and resting behavioral states in healthy fetuses aged 30 to 32 weeks.

METHODS

MCA blood flow was measured by pulsed Doppler sonography 3 times during each fetal behavioral state (active and resting). The average during active state was compared during the resting state. Statistical analysis was performed by paired t test.

RESULTS

During the fetal active state, there was a significant increase in the mean PSV (51.59 cm/s vs 46.95 cm/s, P < .0001) and mean end-diastolic velocity (9.59 cm/s vs 7.98 cm/s, P=.0015), and a significant decrease in the mean pulsatility index (PI) (2.07 vs 2.19, P=.0226) and the mean resistance index (0.83 vs 0.85, P=.0481).

CONCLUSION

Healthy preterm fetuses have a significantly higher MCA PSV during the active state. Activity state should be considered when interpreting MCA Doppler indices.

A retrospective review of isoimmunized pregnancies managed by middle cerebral artery peak systolic velocity

OBJECTIVE

The purpose of this study was to determine the clinical outcome of isoimmunized pregnancies managed primarily by middle cerebral artery peak systolic velocity.

STUDY DESIGN

A retrospective chart review was conducted of isoimmunized pregnancies that underwent ultrasound examinations from January 1, 2001, through May 1, 2003. Ultrasound reports, laboratory tests, and maternal and neonatal charts were reviewed.

RESULTS

Women with a clinically significant red blood cell antibody and titer value were included. The study population consisted of 39 women (40 pregnancies, 42 fetuses). Patients with a middle cerebral artery peak systolic velocity of > or =1.5 MoM were offered amniocentesis. Seven pregnancies had an abnormal middle cerebral artery peak systolic velocity. Three of these infants had significant anemia. Six of the 7 pregnancies required an exchange transfusion. None of the 33 pregnancies (35 neonates) with normal middle cerebral artery peak systolic velocity measurements resulted in a neonate with significant anemia or severe hyperbilirubinemia.

CONCLUSION

The clinical outcome of these pregnancies supports the use of middle cerebral artery peak systolic velocity measurements in the management of isoimmunized pregnancies.

Fetal anemia: new technologies

PURPOSE OF REVIEW

The purpose of this review is to summarize recently published studies on noninvasive diagnosis of fetal anemia in order to give recommendations for the use of these new tools.

RECENT FINDINGS

Red cell alloimmunization remains one of the most common causes of fetal anemia. Amniocentesis and cordocentesis have been used for many years to diagnose fetal anemia due to red cell aloimmunization. These techniques, however, are invasive and many complications are associated with their use. Noninvasive diagnosis of fetal anemia has been performed with Doppler ultrasonography. Based on robust data, several authors recommend the use of middle cerebral artery peak systolic velocity in the management of fetuses at risk for anemia because of red cell alloimmunization. This Doppler parameter can also diagnose fetal anemia due to other conditions.

SUMMARY

Middle cerebral artery peak systolic velocity appears to be the best test for the noninvasive diagnosis of fetal anemia. It is important to emphasize that training of sonographers and sonologists is the 'conditio sine qua non' for the correct sampling of the middle cerebral artery.

Middle Cerebral Artery Doppler Used to Detect Fetal Anemia

Although rhesus immune globulin, also knownas Rhogam, has caused a dramatic decrease inanemic fetal demise, there are still risks. Anestimated one to six anemia cases occur per 1000births each year, but only 30% of these fetuseswill develop anemia that requires treatment.Previously, invasive techniques such ascordocentesis and amniocentesis were the only testsused to diagnosis a fetus at risk for anemia.Recently, anemia has been diagnosed by Dopplersonography of the middle cerebral arteryvelocity. The peak systolic velocities are measuredand plotted on a graph to determine anemiaseverity. These velocities are also able to diagnoseanemia in healthy fetuses by monitoring velocityincreases at a certain gestational age. Timing ofthe first and later intravenous blood transfusionscan also be determined using middle cerebralartery peak systolic velocity Doppler. Thisnoninvasive test has no known risk to the fetus andhas proven very useful in the diagnosis of fetalanemia.

The value of middle cerebral artery peak systolic velocity in the diagnosis of fetal anemia after intrauterine death of one monochorionic twin

OBJECTIVE

The purpose of this study was to assess the value of the fetal middle cerebral artery peak systolic velocity in the prediction of anemia within 24 hours of the death of one monochorionic twin in twin-to-twin-transfusion syndrome and to establish the correlation between middle cerebral artery peak systolic velocity and hemoglobin concentration in fetuses who are at risk for acute anemia.

STUDY DESIGN

Doppler examination of the middle cerebral artery peak systolic velocity was performed in 20 monochorionic survivors of pregnancies that were complicated by twin-to-twin-transfusion syndrome that occurred between 20 and 34 weeks of gestation. Doppler examination was performed before cordocentesis and after intrauterine transfusion when appropriate. Both hemoglobin concentration and middle cerebral artery peak systolic velocity were expressed in multiples of the median. Severe anemia was defined as hemoglobin concentration of <0.55 multiples of the median, and we used the cutoff point of 1.50 times the median values at any gestational age to calculate the sensitivity and specificity of middle cerebral artery peak systolic velocity in detecting moderate or severe anemia.

RESULTS

Fetal anemia was confirmed in 10 of 20 fetuses. We performed seven intrauterine transfusions. The sensitivity and specificity of middle cerebral artery peak systolic velocity in the prediction of severe fetal anemia were of 90%, with a false-negative rate of 10%. The correlation between peak systolic velocity and hemoglobin concentration both before and after transfusion was evaluated by regression analysis and was strongly significant.

CONCLUSION

In fetuses who are at risk of acute anemia, the measurement of middle cerebral artery peak systolic velocity was found to be a reliable noninvasive diagnostic tool and may be helpful in counseling and planning invasive assessment.

Noninvasive tests to predict fetal anemia: a study comparing Doppler and ultrasound parameters

OBJECTIVE

This study was undertaken to compare test characteristics of ultrasound and Doppler parameters in the prediction of fetal anemia in alloimmunized pregnancies.

STUDY DESIGN

In a prospective cohort study, 16 nonhydropic fetuses with red blood cell alloimmunization were evaluated with ultrasound and Doppler imaging. Middle cerebral artery (MCA) peak systolic velocity, intrahepatic umbilical venous (IHUV) maximum velocity, liver length, and spleen perimeter were measured. Results before first fetal blood sampling (FBS) or delivery were analyzed. Fetal anemia was defined as hemoglobin deficit 5 SD or greater. Sensitivity and specificity were calculated.

RESULTS

Six fetuses were anemic and required intrauterine transfusion, and 10 were not severely anemic at birth. MCA Doppler imaging was the best predictor of fetal anemia (100%), followed by IHUV (83%). Sensitivity was low for spleen perimeter (66%) and liver length (33%).

CONCLUSION

Doppler evaluation of MCA peak systolic velocity is better than IHUV maximum velocity, liver, or spleen size in the prediction of fetal anemia in red blood cell alloimmunization.

Anti-E alloimmunization in pregnancy: management dilemmas

Compared to anti-D alloimmunization, anti-E alloimmunization is a less common cause of hemolytic diseases of the newborn. Being a less potent immunogen, clinical manifestations of anti-E alloimmunization are more variable and usually of less severity. However, the clinical obstetric management of these cases of anti-E alloimmunization is just as challenging. We report here the management of a patient with anti-E alloimmunization to illustrate the controversies of invasive and non-invasive monitoring in the management of such cases.