Prenatal cerebral Doppler ultrasonography and neonatal neurologic outcome

Impact of congenital heart disease on fetal brain development and injury

PURPOSE OF REVIEW

Advances in cardiac surgical techniques and intensive care have led to improved survival in babies with congenital heart disease (CHD). Although it is true that the majority of children with CHD today survive, many have impaired neurodevelopmental outcome. Although continuing to improve short-term morbidity and mortality are important goals, recent research has focused on defining the impact of CHD on brain development and brain injury in utero.

RECENT FINDINGS

The impact of CHD on the developing brain of the fetus and infant will be discussed. Neurologic abnormalities detectable prior to surgery will be described and postnatal progression of abnormalities will be highlighted. Potential causes of these findings will be discussed, including altered cerebral blood flow in utero, and brain development and risk for in-utero and postnatal brain injury. Finally, neurologic and developmental outcome after surgical repair of CHD will be reviewed.

SUMMARY

Neurodevelopmental evaluation preoperatively and postoperatively in CHD patients should be standard practice, not only to identify those with impairments who would benefit from intervention services but also to identify risk factors and strategies to optimize outcome. Fetal management and intervention strategies for specific defects may ultimately play a role in improving in-utero hemodynamics and increasing cerebral oxygen delivery to enhance brain development.

Impact of congenital heart disease on brain development and neurodevelopmental outcome

Advances in cardiac surgical techniques and perioperative intensive care have led to improved survival in babies with congenital heart disease (CHD). While it is true that the majority of children with CHD today will survive, many will have impaired neurodevelopmental outcome across a wide spectrum of domains. While continuing to improve short-term morbidity and mortality is an important goal, recent and ongoing research has focused on defining the impact of CHD on brain development, minimizing postnatal brain injury, and improving long-term outcomes. This paper will review the impact that CHD has on the developing brain of the fetus and infant. Neurologic abnormalities detectable prior to surgery will be described. Potential etiologies of these findings will be discussed, including altered fetal intrauterine growth, cerebral blood flow and brain development, associated congenital brain abnormalities, and risk for postnatal brain injury. Finally, reported neurodevelopmental outcomes after surgical repair of CHD will be reviewed.

Use of umbilical-cerebral Doppler ratios in predicting fetal growth restriction in near-term fetuses

OBJECTIVE

To compare the sensitivity and specificity of different umbilical-cerebral ratios in the prediction and detection of fetal growth restriction in near-term fetuses when the umbilical arterial waveform is within normal.

METHODS

A prospective cross-sectional observational study was carried out recruiting consecutive singleton pregnancies with clinically suspected fetal growth restriction after 34 weeks gestation. The umbilical-cerebral ratios were then calculated from the S/D, RI and PI values and correlated with immediate perinatal outcome.

RESULTS

A total of 187 patients were recruited. Twelve cases had abnormal UA Doppler flow velocity waveform studies. Of the 175 with normal UA Doppler findings, 92 (53.1%) were confirmed to have fetal growth restriction (FGR) with birth weights below the tenth centile for gestation. The detection rate of FGR by ultrasound biometry was 96.7%. The mean umbilical artery S/D, RI and PI values were higher in the fetal growth restriction group, while the middle cerebral artery values were lower as compared to fetuses with no growth restriction. A small but significant difference was seen in the umbilical-cerebral ratios of the different indices between the two groups. Receiver operator characteristic curves showed that there was little difference between the performances of the S/D, RI or PI ratios and all had limited power in predicting fetal growth restriction.

CONCLUSION

In the presence of normal umbilical artery Doppler waveforms, umbilical-cerebral ratios have limited power to predict fetal growth restriction.

Autoregulation of cerebral blood flow in fetuses with congenital heart disease: the brain sparing effect

Fetuses with congenital heart disease (CHD) have circulatory abnormalities that may compromise cerebral oxygen delivery. We believe that some CHD fetuses with decreased cerebral oxygen supply have autoregulation of blood flow that enhances cerebral perfusion (brain sparing). We hypothesize that cerebral autoregulation occurs in CHD fetuses, and the degree of autoregulation is dependent on the specific CHD and correlates with intrauterine head circumferences. CHD fetuses were compared to normal fetuses. Data included cardiac diagnosis, cerebral and umbilical artery Doppler, head circumference, weight, and gestational age. The cerebral-to-placental resistance ratio (CPR) was assessed as a measure of cerebral autoregulation. CPR = cerebral/umbilical resistance index (RI) and RI = systolic-diastolic/systolic velocity (normal CPR > 1). CPR > 1 was found in 95% of normal vs 44% of CHD fetuses. The incidence of CPR < 1 was greatest in hypoplastic left or right heart fetuses. Compared to normal, cerebral RI was decreased in CHD fetuses. The CPR vs gestational age relationship, and the relationship among weight, head circumference, and CPR differed across normal and CHD fetuses. Fetuses > 2 kg with CHD and a CPR < 1 had smaller head circumferences than normal. Brain sparing occurs in CHD fetuses. Fetuses with single ventricular physiology are most affected. Inadequate cerebral flow in CHD fetuses, despite autoregulation, may alter brain growth.

Antenatal predictors of the neurologic sequelae at 3 years of age: a multivariate analysis

OBJECTIVE

To study the association between fetal blood flow abnormalities and the occurrence of long-term neurologic sequelae.

STUDY DESIGN

Umbilical, aortic and middle cerebral artery blood flow parameters were obtained by Doppler examination and retrospectively analyzed in 128 high-risk singleton pregnancies, followed by neurologic examination of the surviving children at 3 years of age. Traditional parameters of neurologic outcome (Apgar scores, intrauterine growth retardation (IUGR), umbilical artery pH and base deficit, gestational age, birth weight, newborn encephalopathy, mode of delivery, fetal heart rate, neurosonographic examination) were included as possible confounding factors. Mann-Whitney U-test, Student's t-test, analysis of variance or Fisher's exact test, where applicable, were used for the univariate analysis. A stepwise logistic regression procedure was conducted to test the independent association of selected perinatal risk factors on neurological outcome. Statistical significance was assumed at P<0.05.

RESULTS

Eighteen out of 114 surviving children suffered neurologic illness at 3 years of age. Four children had major neurologic dysfunction and the remaining 14 suffered minor or mild form of the disease. Although blood flow parameters and various perinatal parameters did not differ significantly between the group of children with major neurologic dysfunction and healthy children, aortic resistance index showed an independent association with occurrence of minor or mild neurologic disabilities.

CONCLUSION

Antenatal evaluation of the aortic blood flow might be an important predictive variable for permanent neurologic disturbances.

Behavioural development and Doppler velocimetry in relation to perinatal outcome in small for dates fetuses

Twenty-two small for dates (SFD) fetuses and 96 fetuses from uncomplicated pregnancies were monitored on two occasions between 27 and 32 weeks and the second time between 33 and 36 weeks of gestation by studying the development of behavioural states (coincidence 1F and 2F; no coincidence) and umbilical artery Doppler waveform patterns (UA; Resistance Index, RI). Data were related to neurological outcome at 8 months after birth. The purpose of this study was to investigate if the development of behavioural state is disturbed in SFD fetuses and if SFD fetuses who needed to be delivered early and/or had abnormal neurological outcome showed different state development and RI than SFD fetuses delivered later in pregnancy or with normal neurological outcome. Finally, we studied if there was a relationship between state development and RI. At 27-32 weeks of gestation the percentage of coincidence 2F (C2F%) was lower and the percentage of coincidence 1F (C1F%) and no coincidence (NOC%) were higher in the SFD fetuses than in the control group. At 33-36 weeks C2F% was lower and NOC% was higher but not statistically different (P = 0.2 and P = 0.07, respectively). SFD fetuses who needed to be delivered early had poorer state development than SFD fetuses at lower risk and infants who were abnormal at 8 months of life showed a higher C1F% and lower C2F% at 27-32 weeks. There were significant correlations between RI on the one hand and NOC% (r = 0.62) and C2F% (r = -0.48) on the other hand at 27-32 weeks in the subgroup with abnormal neurological outcome. In conclusion, in SFD fetuses there are disturbances in the development of behavioural states as well in the distribution of the periods of coincidence (with a decrease in C2F% and an increase in C1F%). Poorest state development is present in SFD fetuses at highest risk and in this group there appears to be a significant relationship between the degree of utero-placental insufficiency (RI) and disturbances in behavioural development.

Absence of end-diastolic flow velocity in the umbilical artery: a review

The objective of this review was to find the clinical relevance of the absence of end-diastolic flow velocity in the umbilical artery. Search was conducted through MEDLINE using unabridged MEDLINE Knowledge Finder (Aries System Corp., North Andover, MA). All the manuscripts published in English language within last 10 years (1983-1992) were included in the review process. There has been no report of umbilical artery absent-end diastolic velocity before 1983. It was extremely difficult to draw a conclusion because a majority of the available reports in the literature are either case reports or retrospective analyses. However, for the practical purposes it can be concluded that after viability these pregnancies should be followed by intense (daily) fetal well-being surveillance with conventional antenatal tests. Those who improve their end-diastolic velocity should be allowed to continue the pregnancy as long as antenatal testing is promising. Persistence of absent end-diastolic velocity may be an indication for delivery at a gestational age when there is reasonable chance of survival. Cytogenetic evaluation and anatomical survey of these fetuses by ultrasound is recommended. Long-term follow up of surviving infants needs to be studied. It is impossible for a single institution to accumulate enough cases for adequate outcome evaluation. A randomized prospective trial to assess the management of pregnancies with absent end-diastolic velocity in the umbilical artery would be difficult. Some might even consider such a study unethical. Until such a study is performed, an international registry would be helpful for collecting data about the perinatal outcomes and management of such patients.

Assessment of the fetal PO2 changes by cerebral and umbilical Doppler on lamb fetuses during acute hypoxia

The objective of the present study was to validate one or a combination of fetal Doppler parameters in order to assess acute fetal hypoxia in an ovine model. Acute hypoxia was induced by reducing umbilical, or maternal aortic flow (approx. 70%). A CW Doppler probe was fixed on the fetal cervical skin, facing the internal carotid artery and the fetal abdominal skin adjacent to the umbilical arteries. (The angle between Doppler beam and flow vector remained constant.) A "Doptek 3000" spectrum analyser was used to measure the maximal and mean Doppler frequencies. Heart rate (HR), umbilical blood flow (UBF), carotid blood flow (CBF), umbilical RI (URI), cerebral RI (CRI) and cerebroplacental ratio (CPR = CRI/URI) were calculated in real time. A catheter was inserted into the fetal femoral artery, for blood gas (PO2, PCO2 pH) and blood pressure (BP) measurements. After 1 min of aorta compression (70% aortic flow reduction), the URI increased by 10% (P < 0.05), and the UBF decreased by 10% (P < 0.05), but the CRI decreased by 20% (P < 0.02), and the CBF did not change significantly. Fetal PO2 and CPR fell down after 1 min (59% and 38%, respectively; P < 0.001), although strong fetal heart rate decelerations were observed. The blood pressure, PCO2 and pH did not change significantly during this test. Throughout the 12 min of cord compression (70% umbilical flow reduction) the URI increased (70% to 80% P < 0.001), and the UBF decreased (approx. 60%; P < 0.001), but the CRI decreased (approx. 25%; P < 0.01), and the CBF remained constant (+/- 5%; ns). Fetal PO2 and CPR all decreased during the compression (30% to 44% and 40% to 60%, respectively; P < 0.001). HR, pH and PCO2 did not change significantly. During cord compression the blood pressure did not change significantly. In both cases, the CPR decreased significantly (P < 0.001) with the PO2 in the same direction and with a comparable amplitude (-30% to -50%). Nevertheless, the drop in CPR was greater during cord compression than during aorta compression, probably because the compression of the cord induced a central hypovolemia in addition to the hypoxia. The CPR was found to be the hemodynamic parameter that followed most closely the PO2 acute changes. The amplitude of the variations of this parameter (-30% to -50%) were quite similar to those of the PO2 during the period of acute hypoxia.(ABSTRACT TRUNCATED AT 400 WORDS)

Fetal cerebral and renal Doppler in small for gestational age fetuses in hypertensive pregnancies

The aim of the present work is to evaluate the hemodynamic disorders induced in several fetal vascular areas by maternal hypertension and to check the sensitivity and the specificity of the various Doppler parameters in the detection of small for gestational age (SGA) infants. The population consisted of 90 pregnant mothers aged 26.3 +/- 5.8 years with pregnancy-induced hypertension. Seventeen of them delivered moderate small for age babies (between the 10th and 5th centiles), without any neonatal complication. The opposition to flow in the fetal brain and kidney and in the placenta was evaluated using the Resistance Index (RI). The ratio of cerebral RI and umbilical RI, called the cerebroplacental ratio (CPR), was calculated and used as an indicator of fetal flow redistribution. The ability of CPR and renal RI to predict SGA at birth was evaluated; the sensitivity, specificity, positive predictive value, and negative predictive value for the CPR were 88.2%, 98.6%, 93.8% and 97.3%, respectively. The corresponding figures for the renal RI were 58.8%, 94.5%, 71.4% and 91%, respectively. Furthermore, in the SGA group, the abnormal renal RI values were both above and below the normal range, whereas the CPR values demonstrated consistent changes (always < 1).

CONCLUSION

this investigation demonstrates that in pregnancy-induced hypertension (even with moderate growth retardation, and no neonatal complication), the diagnostic efficacy of CPR for predicting SGA at birth is very high and that of renal RI correlates very poorly with fetal growth.

Doppler ultrasonography in uteroplacental insufficiency

Much of our understanding of uteroplacental insufficiency has been derived from animal research and the study of the pathology of human placental and uterine biopsies. These studies have shown how the placenta plays a major role in the development of normal pregnancy and how placental dysfunction is generally caused by factors interfering with the normal growth of the uteroplacental and/or fetoplacental circulations. These abnormalities lead to a deficient supply of oxygen and nutrients to the fetus and to several complications of pregnancy such as gestational hypertension, preeclampsia and intrauterine growth retardation (IUGR).

Predictors of perinatal outcome in intrauterine growth retardation: a long term study

Fifty-three intrauterine retarded fetuses (IUGR) and seventy-five healthy pregnancies were monitored by neurobehavioural profile (quiet state or S1F and activity state or S2F percentages) and umbilical artery Doppler velocimetry (UA RI) on two occasions between the 27th-32nd and the 33rd-36th week of gestation. The aims of the present study were the following 1) to relate S1F, S2F and RI to mild and severe IUGR 2) to relate behavioural state analysis and UA Doppler velocimetry to the following perinatal outcomes: Cesarean section (CS); Preterm delivery (PD); small for gestational age (SGA); Apgar score at 1st and 5th min < 7; Respiratory Distress Syndrome (RDS); Neurological Injury (NI) (evaluated at the birth, the 4th, the 8th and the 12th month of life). 3) to establish the best predictors of perinatal outcome with these monitoring parameters by a stepwise computerized processing. Our results suggest: 1) mild IUGR, characterized by a progressive increase in peripheral vascular resistances, positive diastolic peak flow (RI: 0.72 +/- 0.01; mean +/- SD), is associated with gradual increase in S1F (12.51 +/- 2.84; mean +/- SD) and a decrease in S2F (27.51 +/- 2.81; mean +/- SD) percentages; 2) severe IUGR, characterized by zero or negative diastolic peak flow (UA RI-->1), is associated with a significant increase in S1F (21.32 +/- 12.11; mean +/- SD) and a decrease in S2F percentages (30.93 +/- 20.35; mean +/- SD).

IN CONCLUSION

S1F is the best predictor of severe IUGR and significant for all the perinatal outcomes selected; S2F is the best predictor of mild IUGR and significant for SGA; UA RI is the best parameter for recognizing mild IUGR and evolution to severe IUGR.

Fetal intracranial haemorrhage: clinical significance of in utero ultrasonographic diagnosis

OBJECTIVE

To review in utero detection of fetal intracranial haemorrhage.

DESIGN

Retrospective survey of pregnant women presenting to the ultrasonographic unit in whom the diagnosis of fetal intracranial haemorrhage was reached.

SETTING

The Chaim Sheba Medical Center in Ramat Gan, and Shaare Zedek Medical Center in Jerusalem; two large district general hospitals, each with 6000 maternity patients per year.

SUBJECTS

Five fetuses with gestational ages ranging from 26 to 36 weeks.

MAIN OUTCOME MEASURES

Maternal complications, fetal monitoring, prenatal Doppler ultrasound studies, postnatal imaging studies, neonatal morbidity and mortality.

RESULTS

Transabdominal sonography showed hyperechoic lesions in the brain parenchyma, and the lateral ventricle in three of five fetuses. In the remaining two fetuses, transvaginal sonography enhanced the visualisation of ventriculomegaly with intraventricular haemorrhage in one and periventricular leukomalacia was identified in the second. Three fetuses were appropriate for gestational age, and two were severely growth retarded. In one woman severe pre-eclamptic toxaemia may explain intracranial haemorrhage. Abnormal nonstress test and abnormal flow velocity waveforms in the umbilical and cerebral arteries were present in the two growth retarded fetuses, and in one who was appropriate for gestational age. The two growth retarded fetuses died shortly after birth. Of the three surviving infants, two had normal long term development, and one developed hydrocephalus with subsequent severe neurodevelopmental retardation, dying at the age of seven months.

CONCLUSIONS

This small series shows that intracranial haemorrhage has a broad spectrum of manifestations with diverse prognosis. Following an antenatal diagnosis of intracranial haemorrhage, the obstetrician must give special consideration to electronic fetal heart monitoring and Doppler velocity waveforms. The prenatal diagnosis of intracranial haemorrhage has medico-legal implications suggesting that neurological outcome may not necessarily be due solely to intrapartum events and management.

Normal auditory brain stem evoked responses in infants of diabetic mothers

Auditory brain stem responses potentials were recorded from 71 newborns within the first 2 weeks after birth; conceptional age ranged from 37 to 41 weeks. Thirty-nine newborns were infants of diabetic mothers (IDMs) (17 White A, 22 White B-D) and 32 healthy term newborns served as control group. IDMs with additional high risk for cochlear or brain stem integrity were excluded. Birthweight for gestational age was significantly higher for IDMs. No differences in auditory brain stem responses wave latencies or amplitudes were observed between healthy infants of the control group and IDMs.

Cerebral Doppler studies in the fetus and newborn infant

The goal of developing reliable commercial Doppler systems for measuring vessel diameter and velocity changes during the cardiac cycle appears to be near. Reaching this goal would enable us to obtain volume-flow information continuously. In animal experiments, continuous measurements of Doppler velocity, pressure, and flow add important insights into hemodynamic measurements. Incorporating Doppler methods in microcirculatory research could also provide a link between the microcirculatory and the macrocirculatory hemodynamic research. Although Doppler methods have been validated, Doppler findings in clinical research (using commercial systems) must be considered at best to reflect qualitative circulatory alterations indicating directions of change. Because of inherent technologic limitations and considerable intersubject and intrasubject variability, direct extrapolation of the numeric findings from one study to the other can lead to misleading conclusions. The Doppler results are also influenced by measurement conditions and equipment settings. However, Doppler-derived information can be used as an adjunct to clinical management in many of the diseases discussed above. As with any physiologic variable, serial measurements probably are of greater value than single measurements. With continued improvement in technology, Doppler methods hold promise of becoming an important adjunct in cerebral hemodynamic monitoring in perinatal-neonatal intensive care units.

Doppler assessment of the fetal and uteroplacental circulation during nifedipine therapy for preterm labor

To investigate the effects of nifedipine on the human fetal circulation, 11 fetuses whose mothers were treated with nifedipine for treatment of preterm labor were studied. Maximum velocity waveforms were obtained in the middle cerebral artery (n = 8), renal artery (n = 6), ductus arteriosus (n = 8), and umbilical artery (n = 10). Transvalvular maximal velocity waveforms were obtained across the aortic (n = 11) and pulmonary (n = 7) valves. Maternal uterine arteries also were studied (n = 7). Doppler data were collected before and 5 hours after nifedipine therapy. Patients received an oral loading dose of 30 mg of nifedipine followed by a second oral dose of 20 mg 4 hours later. No significant difference in the flow velocity waveforms was found in the vessels studied 5 hours after the initial dose. These results suggest that short-term nifedipine therapy does not influence either fetal or uteroplacental circulation as evaluated with the Doppler technique.