Fetal brain sparing is associated with accelerated shortening of visual evoked potential latencies during early infancy

Neurodevelopmental Outcomes following Intrauterine Growth Restriction and Very Preterm Birth

OBJECTIVES

To evaluate whether intrauterine growth restriction (IUGR) adds further neurodevelopmental risk to that posed by very preterm birth alone in terms of alterations in brain growth and poorer toddlerhood outcomes.

STUDY DESIGN

Participants were 314 infants of very preterm birth enrolled in the Evaluation of Preterm Imaging Study (e-Prime) who were subsequently followed up in toddlerhood. IUGR was identified postnatally from discharge records (n = 49) and defined according to prenatal evaluation of growth restriction confirmed by birth weight <10th percentile for gestational age and/or alterations in fetal Doppler. Appropriate for gestational age (AGA; n = 265) was defined as birth weight >10th percentile for gestational age at delivery. Infants underwent magnetic resonance imaging at term-equivalent age (median = 42 weeks); T2-weighted images were obtained for voxelwise gray matter volumes. Follow-up assessments were conducted at corrected median age of 22 months using the Bayley Scales of Infant and Toddler Development III and the Modified-Checklist for Autism in Toddlers.

RESULTS

Infants of very preterm birth with IUGR displayed a relative volumetric decrease in gray matter in limbic regions and a relative increase in frontoinsular, temporal-parietal, and frontal areas compared with peers of very preterm birth who were AGA. At follow-up, toddlers born very preterm with IUGR had significantly lower cognitive (effect size = 0.42) and motor (effect size = 0.41) scores and were more likely to have a positive Modified-Checklist for Autism in Toddlers screening for autism (OR = 2.12) compared with peers of very preterm birth who were AGA.

CONCLUSIONS

IUGR might confer a neurodevelopmental risk that is greater than that posed by very preterm alone, in terms of both alterations in brain growth and poorer toddlerhood outcomes.

Neurodevelopment of infant with late fetal growth restriction

Late fetal growth restriction has increasingly gain interest. Differently from early fetal growth restriction, the severity of this condition and the impact on perinatal mortality and morbidity is less severe. Nevertheless, there is some evidence to suggest that fetuses exposed to growth restriction late in pregnancy are at increased risk of neurological dysfunction and behavioral impairment. The aim of our review was to discuss the available evidence on the neurodevelopmental outcome in fetuses exposed to growth restriction late in pregnancy. Cerebral blood flow redistribution, a Doppler hallmark of late fetal growth restriction, has been associated with this increased risk, although there are still some controversies. Currently, most of the available studies are heterogeneous and do not distinguish between early and late fetal growth restriction when evaluating the long-term outcome, thus, making the correlation between late fetal growth restriction and neurological dysfunction difficult to interpret. The available evidence suggests that fetuses exposed to late growth restriction are at increased risk of neurological dysfunction and behavioral impairment. The presence of the cerebral blood flow redistribution seems to be associated with adverse neurodevelopmental outcome, however, from the present literature the causality cannot be ascertained.

Knowledge Gaps and Emerging Research Areas in Intrauterine Growth Restriction-Associated Brain Injury

Intrauterine growth restriction (IUGR) is a complex global healthcare issue. Concerted research and clinical efforts have improved our knowledge of the neurodevelopmental sequelae of IUGR which has raised the profile of this complex problem. Nevertheless, there is still a lack of therapies to prevent the substantial rates of fetal demise or the constellation of permanent neurological deficits that arise from IUGR. The purpose of this article is to highlight the clinical and translational gaps in our knowledge that hamper our collective efforts to improve the neurological sequelae of IUGR. Also, we draw attention to cutting-edge tools and techniques that can provide novel insights into this disorder, and technologies that offer the potential for better drug design and delivery. We cover topics including: how we can improve our use of crib-side monitoring options, what we still need to know about inflammation in IUGR, the necessity for more human post-mortem studies, lessons from improved integrated histology-imaging analyses regarding the cell-specific nature of magnetic resonance imaging (MRI) signals, options to improve risk stratification with genomic analysis, and treatments mediated by nanoparticle delivery which are designed to modify specific cell functions.

Intrinsic Functional Connectivity in Preterm Infants with Fetal Growth Restriction Evaluated at 12 Months Corrected Age

Fetal growth restriction (FGR) affects brain development in preterm infants, but little is known about its effects on resting-state functional connectivity. We compared 20 preterm infants, born at <34 weeks of gestation with abnormal antenatal Doppler measurements and birth weights <10th percentile, with 20 appropriate for gestational age preterm infants of similar gestational age and 20 term infants. They were scanned without sedation at 12 months of age and screened for autistic traits at 26 months. Resting functional connectivity was assessed using group independent component analysis and seed-based correlation analysis. The groups showed 10 common resting-state networks involving cortical, subcortical regions, and the cerebellum. Only infants with FGR showed patterns of increased connectivity in the visual network and decreased connectivity in the auditory/language and dorsal attention networks. No significant differences between groups were found using seed-based correlation analysis. FGR infants displayed a higher frequency of early autism features, related to decreased connectivity involving the salience network, than term infants. These data suggest that FGR is an independent risk factor for disrupted intrinsic functional connectivity in preterm infants when they are 1-year old and provide more clues about the neurodevelopmental abnormalities reported in this population.

Physiological adaptation of the growth-restricted fetus

The growth-restricted fetus in utero is exposed to a hostile environment and suffers undernutrition and hypoxia. To cope with the stress, the fetus changes its physiological functions. These adaptive changes aid intrauterine survival; however, they can lead to permanent functional and structural changes that can contribute to the development of serious chronic diseases later in life. Epigenetic mechanisms are an important part of the pathophysiological processes behind this "developmental origin of adult diseases." The dominant cardiovascular adaptive change is the redistribution of blood flow in hypoxic fetuses, with preferential supply of blood to the fetal brain, myocardium, and adrenal glands. The proportion of blood from the umbilical vein to the ductus venosus and foramen ovale increases, which increases the cardiac output of the left heart ventricle. The increased perfusion of fetal brain can be followed with Doppler ultrasound as increased diastolic velocities and decreased pulsatility index in the middle cerebral artery.

Impact of cerebral redistribution on neurodevelopmental outcome in small-for-gestational-age or growth-restricted babies: a systematic review

OBJECTIVES

To review systematically the evidence on impact of cerebral redistribution, as assessed by fetal middle cerebral artery (MCA) Doppler, on neurological outcomes in small-for-gestational-age (SGA) or growth-restricted fetuses.

METHODS

For this systematic review, MEDLINE was searched for all controlled studies reporting neurological outcomes in SGA or growth-restricted babies with cerebral redistribution based on MCA Doppler indices, from inception to September 2013. We used relative risk or odds ratios, with 95% CI, to identify the association of cerebral redistribution with neurological outcomes.

RESULTS

The search yielded 1180 possible citations, of which nine studies were included in the review, with a total of 1198 fetuses. Definitions of SGA and cerebral redistribution were variable, as was study quality. Data could not be synthesized in meta-analyses because of heterogeneity in outcome reporting. Cerebral redistribution was not associated with increased risk of intraventricular hemorrhage in neonates (five studies; n = 806). When present in preterm fetuses, cerebral redistribution was associated with normal Neonatal Behavioral Assessment Scale (NBAS) scores at 40 weeks (one study; n = 62) but abnormal psychomotor development at 1 year of age on the Bayley scale (one study; n = 172). When present in term SGA fetuses, cerebral redistribution was associated with increased risk of motor and state organizational problems on NBAS (two studies; n = 158), and lower mean percentile scores in communication and problem solving at 2 years of age on the Ages and Stages Questionnaire (one study; n = 125).

CONCLUSIONS

SGA fetuses with cerebral redistribution may be at higher risk of neurodevelopmental problems. More data are needed from adequately controlled studies with long-term follow-up before conclusions can be drawn. If these findings are true, there is a need to re-evaluate timing of delivery in the management of SGA fetuses, particularly when cerebral redistribution is found at term gestation.

Neurodevelopment after fetal growth restriction

Fetal growth restriction (FGR) can emerge as a complication of placental dysfunction and increases the risk for neurodevelopmental delay. Marked elevations of umbilical artery (UA) Doppler resistance that set the stage for cardiovascular and biophysical deterioration with subsequent preterm birth characterize early-onset FGR. Minimal, or absent UA Doppler abnormalities and isolated cerebral Doppler changes with subtle deterioration and a high risk for unanticipated term stillbirth are characteristic for late-onset FGR. Nutritional deficiency manifested in lagging head growth is the most powerful predictor of developmental delay in all forms of FGR. Extremes of blood flow resistance and cardiovascular deterioration, prematurity and intracranial hemorrhage increase the risks for psychomotor delay and cerebral palsy. In late-onset FGR, regional cerebral vascular redistribution correlates with abnormal behavioral domains. Irrespective of the phenotype of FGR, prenatal tests that provide precise and independent stratification of risks for adverse neurodevelopment have yet to be determined.

Normal visual evoked potentials in preschool children born small for gestational age

AIM

Previous studies have shown visual evoked potential (VEP) abnormalities in infants and animals born small for gestational age (SGA) compared with controls. The current exploratory study aims to investigate whether VEP abnormalities persist in older ages.

METHODS

Pattern VEP latencies were obtained in 21 children (11 girls, 10 boys), born SGA and moderately preterm, at an average age of 5 years and 8 months. Fifty-one children (24 girls, 27 boys, mean age of 5 years and 7 months), also born moderately preterm but with normal height and weight at birth, served as controls

RESULTS

Visual evoked potential results showed no significant differences in latency between children born SGA and controls born appropriate for gestational age (AGA) for either binocular stimulation, right eye or left eye stimulation.

CONCLUSIONS

Our findings do not indicate any differences in VEP latency at preschool age for children born SGA compared with children born AGA. The results may support previous studies, suggesting that children born SGA show accelerated neurophysiologic maturation during their first year of life and that previously delayed VEP latencies after catch-up stay unchanged compared with controls.

Neurodevelopment following fetal growth restriction and its relationship with antepartum parameters of placental dysfunction

Placental dysfunction leading to fetal growth restriction (FGR) is an important risk factor for neurodevelopmental delay. Recent observations clarify that FGR evolves prenatally from a preclinical phase of abnormal nutrient and endocrine milieu to a clinical phase that differs in characteristics in preterm and term pregnancies. Relating childhood neurodevelopment to these prenatal characteristics offers potential advantages in identifying mechanisms and timing of critical insults. Based on available studies, lagging head circumference, overall degree of FGR, gestational age, and umbilical artery (UA), aortic and cerebral Doppler parameters are the independent prenatal determinants of infant and childhood neurodevelopment. While head circumference is important independent of gestational age, overall growth delay has the greatest impact in early onset FGR. Gestational age has an overriding negative effect on neurodevelopment until 32-34 weeks' gestation. Accordingly, the importance of Doppler status is demonstrated from 27 weeks onward and is greatest when there is reversed end-diastolic velocity in the UA or aorta. While these findings predominate in early-onset FGR, cerebral vascular impedance changes become important in late onset FGR. Abnormal motor and neurological delay occur in preterm FGR, while cognitive effects and abnormalities that can be related to specific brain areas increase in frequency as gestation advances, suggesting different pathophysiology and evolving vulnerability of the fetal brain. Observational and management studies do not suggest that fetal deterioration has an independent impact on neurodevelopment in early-onset FGR. In late-onset FGR further research needs to establish benefits of perinatal intervention, as the pattern of vulnerability and effects of fetal deterioration appear to differ in the third trimester.

Killing Me Softly: The Fetal Origins Hypothesis

In the epidemiological literature, the fetal origins hypothesis associated with David J. Barker posits that chronic, degenerative conditions of adult health, including heart disease and type 2 diabetes, may be triggered by circumstance decades earlier, in utero nutrition in particular. Economists have expanded on this hypothesis, investigating a broader range of fetal shocks and circumstances and have found a wealth of later-life impacts on outcomes including test scores, educational attainment, and income, along with health. In the process, they have provided some of the most credible observational evidence in support of the hypothesis. The magnitude of the impacts is generally large. Thus, the fetal origins hypothesis has not only survived contact with economics, but has flourished.

Behavioural problems at the age of eleven years in preterm-born children with or without fetal brain sparing: a prospective cohort study

BACKGROUND

In severe intrauterine growth restriction (IUGR) due to placental insufficiency a haemodynamic adaptation occurs, resulting in preferential blood flow to the fetal brain (brain sparing). With Doppler ultrasound an increased ratio between the umbilical and the cerebral artery pulsatility index (U/C ratio) can be demonstrated. IUGR is associated with impaired neurodevelopmental outcome.

OBJECTIVE

Evaluation of the effect of fetal brain sparing on behavioural problems at eleven years in premature born children.

METHODS

Prospective cohort study in premature children born in 1989, with a gestational age of 26 0/7 to 33 0/7 weeks. An U/C ratio>0.72 was defined as brain sparing. Behavioural problems were assessed with the parent-reported Child Behaviour Check List (CBCL) and the Teacher's Report Form (TRF). T scores >60 for total problem score and subscales of internalizing and externalizing behaviour, were considered abnormal.

RESULTS

Ninety-eight of the 116 survivors were assessed, of which 31 with antenatally established fetal brain sparing. According to the CBCL-total problem score 23.3% of the premature born babies in the brain sparing group had behavioural problems compared with 22.8% of those without brain sparing. According to the TRF-total problem score the percentages were 21.4% and 20.0%, respectively. Logistic regression analysis failed to show a significant association of U/C ratio with behavioural problems. In this model oxygen dependency at 28 days, IQ<85 at five years, cranial ultrasound abnormalities, fetal growth ratio<0.80, Apgar scores<7 after 5 min and birth weight<p10 contributed significantly.

CONCLUSION

In this cohort brain sparing itself has no significant association with behavioural problems at eleven years.

Doppler indices of the middle cerebral artery in fetuses with cardiac defects theoretically associated with impaired cerebral oxygen delivery in utero: is there a brain-sparing effect?

OBJECTIVES

To assess changes in the Doppler flow profiles of the middle cerebral artery in fetuses with cardiac defects theoretically associated with impaired cerebral oxygen delivery in utero.

METHODS

Z-scores were calculated for pulsatility and resistance indices (PI and RI, respectively) of the middle cerebral artery (MCA) and the cerebroplacental ratio (CPR) between 19 and 41 weeks' gestation, and for head circumference at birth (HC), in 113 fetuses with the following isolated cardiac defects: transposition of the great arteries (TGA; n = 18), hypoplastic left heart (HLH; n = 46), severe aortic stenosis (n = 17), pulmonary atresia (n = 18) and tetralogy of Fallot (TOF; n = 14). Pregnancies with uteroplacental dysfunction (indicated by increased uterine and/or umbilical Doppler indices), growth restriction, extracardiac malformations, chromosomal anomalies as well as multiple pregnancies were excluded to avoid any additional hypoxemic effect as strictly as possible. The results were compared with 1378 normal controls.

RESULTS

Fetuses with pulmonary atresia, severe aortic stenosis and TOF had no significant alterations of Doppler parameters or HC at birth. In fetuses with TGA, mean Z-scores of HC at birth were significantly smaller compared with controls (mean +/- SD, -0.73 +/- 1.25; P < 0.05), but there was no significant difference in the Doppler parameters. Fetuses with HLH had significantly lower MCA-PI (-0.57 +/- 0.74; P < 0.05), MCA-RI (-0.73 +/- 0.85; P < 0.05), CPR (-1.44 +/- 1.05; P < 0.05) and HC (-0.50 +/- 1.24; P < 0.05) Z-scores compared with controls.

CONCLUSIONS

Fetuses with cardiac defects theoretically associated with markedly impaired cerebral oxygen delivery in utero (TGA and HLH) have smaller HCs at birth. However, only fetuses with HLH have cerebrovascular alterations that are detectable by evaluation of the Doppler indices MCA-PI, MCA-RI and CPR.

Fetal neurological assessment using noninvasive magnetoencephalography

SQUID Array for Reproductive Assessment is a unique magnetoencephalography device designed for the noninvasive recording of fetal brain activity. In this article, we provide a general overview of the technology and its potential application to fetal medicine. A large number of studies that have been conducted and published describing this device since it was brought into operation are referenced throughout the article.

Intrauterine growth restriction due to uteroplacental insufficiency decreased white matter and altered NMDAR subunit composition in juvenile rat hippocampi

Uteroplacental insufficiency (UPI), the major cause of intrauterine growth restriction (IUGR) in developed nations, predisposes to learning impairment. The underlying mechanism is unknown. Neuronal N-methyl-d-aspartate receptors (NMDARs) are critical for synaptogenesis and learning throughout life. We hypothesized that UPI-induced IUGR alters rat hippocampal NMDAR NR2A/NR2B subunit ratio and/or NR1 mRNA isoform expression and synaptic density at day 21 (P21). To test this hypothesis, IUGR was induced by bilateral uterine artery ligation of the late-gestation Sprague-Dawley dam. At P21, hippocampal NMDAR subunit mRNA and protein were measured, as were levels of synaptophysin. Neuronal, synaptic, and glial density in CA1, CA3, and dentate gyrus (DG) was assessed by immunofluorescence. IUGR increased NR1 mRNA isoform NR1-3a and 1-3b expression in both sexes. In P21 males, IUGR increased protein levels of NR1 C2′ and decreased NR1 C2, NR2A, and the NR2A-to-NR2B ratio, whereas in females, IUGR increased NR2B protein. In males, IUGR was associated with decreased myelin basic protein-to-neuronal nuclei ratio in CA1, CA3, and DG. We conclude that IUGR has sex-specific effects and that neither neuronal loss nor decreased synaptic density appears to account for the changes in NMDAR subunits. Rather, it is possible that synaptic NMDAR subunit composition is altered. Our results suggest that apparent recovery in the IUGR hippocampus may be associated with synaptic hyperexcitability. We speculate that the NMDAR plays an important role in IUGR-associated cognitive impairment.

Quality of general movements in term infants with asphyxia

BACKGROUND

Perinatal asphyxia may result in a developmental disorder. A recently developed non-invasive tool to investigate brain function at an early age is the assessment of general movements (GMs).

AIM

To evaluate relationships between perinatal risk factors and the quality of GMs in the neonatal period and at 3 months in term newborns with asphyxia in a secondary paediatric setting.

METHODS

64 term (>36 weeks postmenstrual age (PMA)) infants with perinatal asphyxia were studied. GMs were assessed at 'writhing' GM age (38-47 weeks PMA) and at 'fidgety' GM age (48-56 weeks PMA). Pre- and perinatal factors were collected in a standardized way.

RESULTS

Multivariate analysis revealed that DA GMs at 'writhing' age mainly correlated with asphyxia related illness. DA GMs at 'fidgety' age correlated in particular with abnormalities on the neonatal ultrasound scan of the brain.

CONCLUSION

In secondary paediatric settings GM-assessment especially around 3 months is a valuable tool for the assessment of the integrity of the nervous system in term infants with asphyxia.

What is spared by fetal brain-sparing? Fetal circulatory redistribution and behavioral problems in the general population

Intrauterine growth restriction has been linked to infant behavioral problems. While typically only birth weight is examined, here the authors assessed fetal circulatory redistribution, also called the "brain-sparing effect," which is a fetal adaptive reaction to placental insufficiency. They aimed to investigate whether fetal circulatory redistribution protects against behavioral problems. Within the Generation R Study (Rotterdam, the Netherlands, 2003-2007), fetal circulation variables for the umbilical artery and the middle and anterior cerebral arteries were assessed with Doppler ultrasound in late pregnancy. Ratios between placental resistance and cerebral resistance were related to behavioral problems, as measured by the Child Behavior Checklist, in 935 toddlers aged 18 months. The umbilical/anterior cerebral ratio was associated with the Total Problems summary score from the Child Behavior Checklist (per standard-deviation increase, odds ratio = 1.2, 95% confidence interval: 1.0, 1.5). Children with higher umbilical/anterior cerebral ratios had higher risks of internalizing problems, emotional reactivity, somatic complaints, and attention problems. A high umbilical/middle cerebral ratio was related to higher scores on the Internalizing and Somatic Complaints scales. The authors conclude that infants with circulatory redistribution in gestation are more likely to have behavioral problems. This suggests that "brain-sparing" does not completely spare the brain and indicates underlying pathology with consequences for later behavior.

Prediction and perinatal outcomes of fetal growth restriction

Assessment of fetal growth and wellbeing is one of the major purposes of antenatal care. Some fetuses have smaller than expected growth in utero and while some of these fetuses are constitutionally small, others have failed to meet their growth potential, that is they are growth restricted. While severe growth restriction is uncommon, the consequences of it being undetected may include perinatal death or severe morbidity. It is, therefore, important to have strategies in place to detect the fetus at risk of growth restriction. These would include an assessment of 'prior risk' from maternal history and examination combined with the results of biochemical and ultrasound investigations, the most promising of which are uterine artery Doppler and biochemistry. We discuss some of the factors to consider when stratifying the obstetric population into degrees of likelihood for growth restriction, and discuss aspects of the management and outcome of pregnancies complicated by growth restriction.

Early maturation of sinus rhythm dynamics in high-risk fetuses

OBJECTIVE

The purpose of this study was to compare cardiac dynamics of high-risk and low-risk fetuses using beat to beat variability.

STUDY DESIGN

This study obtained 214 fetal magnetocardiography recordings from a group of high-risk fetuses with maternal conditions associated with placental insufficiency with the risk of developing intrauterine growth restriction or were already diagnosed with intrauterine growth restriction. For purpose of comparison, another 136 recordings were obtained from low-risk fetuses. The cardiac beat-to-beat intervals computed as RR intervals were analyzed from both groups using the mean and median interval, standard deviation of normal-to-normal intervals, root mean square of the successive differences, and the fraction of the normal-to-normal intervals (pNNx) that differ by more than the chosen tolerance level of 'x' milliseconds from the previous normal-to-normal intervals. Tests for significance between high-risk and low-risk fetuses were calculated using an independent samples t test within the following gestational age groups, 27-30 weeks, 31-35 weeks, and 36-40 weeks.

RESULTS

The root mean square of the successive differences, and the pNNx showed a significant difference between the low-risk and high-risk fetuses in the 31-35-week and the 36-40-week divisions. In the 31-35-week age division, low-risk fetuses had significantly lower root mean square of the successive differences, and pNN values than the high risk, but in the 36-40-week division, the low-risk fetuses had significantly higher root mean square of the successive differences, and pNN values.

CONCLUSION

Cardiac dynamics for fetuses of mothers at risk for placental insufficiency mature quicker than fetuses not at risk for placental insufficiency.

Visual function at 11 years of age in preterm-born children with and without fetal brain sparing

OBJECTIVE

We have demonstrated earlier an accelerated maturation of the visual evoked potential in the first year of life in preterm infants with antenatal brain sparing. We have now assessed visual functioning at 11 years of age in the same cohort and compared the groups with and without brain sparing.

DESIGN/METHODS

One hundred sixteen survivors included in a study on the outcome of preterm infants born at <33 weeks' gestation with and without fetal brain sparing and admitted to the NICU were followed extensively. Ninety-eight infants (85%) were again assessed at 11 years of age. Data were available for fetal Doppler measurements indicating brain sparing, neonatal cerebral ultrasound scanning, and developmental outcome in the first 5 years. Mean birth weight was 1303 g; mean gestational age was 29.8 weeks. The infants were divided into 2 groups with and without brain sparing. Visual functioning was estimated by measuring visual acuity, visual fields, eye position, and binocular function and by visual motor tests.

RESULTS

Six percent of the children were found to have a visual acuity of <0.8, 12% had strabismus, and 14% to 46% showed abnormal results on the visual motor tests. No statistical differences were found between the 2 groups. However, children with severe cerebral ultrasound diagnoses in the neonatal period were found to have significantly more abnormalities on visual functioning and lower scores on visual motor tests than children without these morbidities.

CONCLUSIONS

Children with fetal brain sparing do not demonstrate a different development of their visual functioning at late school age. However, an abnormal cerebral ultrasound in the neonatal period is associated with impaired visual function in later life.

A population-based study of 518 very preterm neonates from high-risk pregnancies: Prognostic value of umbilical and cerebral artery Doppler velocimetry for mortality before discharge and severe neurological morbidity

OBJECTIVE

To evaluate in everyday practice the predictiveness of fetal umbilical artery and cerebral artery Doppler examination for mortality before discharge and for severe neurological morbidity among very preterm neonates from high-risk pregnancies.

METHODS

Data came from a population-based study (EPIPAGE) of all births before 33 weeks' gestation during 1 year in nine French regions. We examined the prognostic value of Doppler findings among the liveborn singletons delivered after pregnancies with maternal hypertension or antenatal suspicion of small-for-gestational-age status.

RESULTS

This study included 518 fetuses. Predischarge mortality for infants with abnormal umbilical artery Doppler findings was not significantly higher than for those with normal findings. Mortality for infants with abnormal cerebral artery Doppler findings was significantly higher in the bivariate analysis (crude OR: 3.5 (1.6-7.4)). After adjustment, the association between mortality and abnormal cerebral artery Doppler findings remained significant in the subgroup with an abnormal umbilical artery Doppler assessment (OR: 5.1 (1.1-23)). There was no significant association between neurological morbidity and Doppler findings.

CONCLUSION

The prognostic value of Doppler examinations appears lower in this study than in previous hospital series. This suggests the need for quality control and improvements in these examinations.

Assessment of gestational age and neuromaturation

Neuromaturation is the functional development of the central nervous system (CNS). It is by its very nature a dynamic process, a continuous interaction between the genome and first the intrauterine environment, then the extrauterine environment. Understanding neuromaturation and being able to measure it is fundamental to infant neurodevelopmental assessment. Fetal and preterm neuromaturation has become easier to observe with the advent of prenatal ultrasonography and neonatal intensive care units. A number of measures of degree of fetal maturation have been developed and used to estimate gestational age (GA) at birth. The most reliable measures of GA are prenatal measures, especially from the first trimester. Postnatal GA measurements tend to be least accurate at the extremes of gestation, that is, in extremely preterm and post-term infants. Observations of measures of neuromaturation in infants born to mothers with pregnancy complications, including intrauterine growth restriction, multiple gestation, and chronic hypertension, have led to the discovery that stressed pregnancies may accelerate fetal pulmonary and CNS maturation. This acceleration of neuromaturation does not occur before 30 weeks' gestation and has a cost with respect to cognitive limitations manifested in childhood. The ability to measure fetal and preterm neuromaturation provides an assessment of neurodevelopmental progress that can be used to reassure parents or identify at risk infants who would benefit from limited comprehensive follow-up and early intervention services. In addition, measures of neuromaturation have the potential to provide insight into mechanisms of CNS injury and recovery, much-needed early feedback in intervention or treatment trials and a measure of early CNS function for research into the relationships between CNS structure and function.

Electrographic imaging of recognition memory in 34–38 week gestation intrauterine growth restricted newborns

Electrophysiological imaging of recognition memory using event-related potentials (ERPs) in intrauterine growth-restricted (IUGR) newborns allows assessment of recognition memory before the onset of multiple confounding variables. Animal models that reproduce the physiologic components associated with IUGR have demonstrated adverse effects on the hippocampus, a structure that is essential to normal memory processing. Previous electrophysiologic studies have demonstrated shortened auditory-evoked potential (AEP) and visual-evoked potential (VEP) latencies in IUGR infants suggesting accelerated neural maturation in response to the adverse in-utero environment. The hypothesis of the current study was that newborns with IUGR and head-sparing would demonstrate altered auditory recognition memory when compared to controls and that the configuration of the alteration would evidence advanced maturation but still be different from that of typically grown newborns. Twelve IUGR newborns born at 34-38 weeks gestation with head-sparing and 16 age-matched control newborns were tested with both a speech/nonspeech paradigm to assess auditory sensory processing and a novel (stranger's voice) and familiar (mother's voice) paradigm to assess recognition memory. In the recognition memory experiment, a three-way interaction of condition, lead, and group was identified for the lateral leads T4, CM3, and CM4 with the response to the mother being of much greater area in the IUGR cohort than in the controls. This ERP configuration has previously been reported for the midline leads in term newborns. The findings indicate that IUGR newborns with head-sparing have electrophysiologic evidence of accelerated maturation of cognitive processing suggesting an atypical process of maturation that may not support typical cognitive development.

Functional development of the visual system in human fetus using magnetoencephalography

The development of the human brain in utero is normally regarded as a dynamic process involving mainly structural and quantitative changes in neurons and their distribution. However, it is generally accepted that a parallel development of functional specialization occurs in certain areas of the brain, especially in the primary cortex. Nearly all knowledge of functional fetal brain development has been obtained from various animal studies rather than human studies. These studies show that the primary sensory areas like auditory, visual, and somatosensory cortex show a basic function similar to that of a fully developed brain. It has been specifically shown that the visual system develops during fetal life and becomes functional before birth. Several studies have demonstrated the feasibility of using visual evoked response (VER) recordings on preterm human infants to follow the functional development of the visual system. With the advent of the noninvasive technique of magnetoencephalography (MEG), human fetal VER recordings are now possible thus providing the opportunity to track its functional development with gestation. We present and discuss the results of VER recordings in human fetuses starting at 28 weeks of gestation performed using a 151-channel MEG system.

Paediatric consequences of fetal growth restriction

The evidence for outcome following fetal growth restriction (FGR) has previously been inferred from studies, based on babies who were born small for gestational age (SGA). Great care is required when evaluating studies in this area due to a number of potential confounders. It does appear, however, that FGR is associated with an increased risk of poor neurological outcome. This includes an increased risk of cerebral palsy in babies greater than 32 weeks' gestation. Below 32 weeks, the effects of prematurity appear to negate the effects of FGR. FGR is also associated with cognitive deficit and behaviour problems. Babies with poor prenatal head growth appear to have a worse cognitive outcome. However, the role of 'fetal brain sparing' remains unclear, as impaired cognitive outcome is still evident in babies with appropriate head growth. Recent studies, which have identified FGR more accurately using fetal growth standards, have found an increased incidence of major intracranial injury and other adverse neonatal outcomes, which had previously been thought to occur less frequently in FGR babies. FGR is also associated with poor postnatal growth. The majority of children with FGR demonstrate catch-up growth in the first 2 years of life. Children who fail to demonstrate catch-up growth have a high risk of long-term growth problems. There is evidence of impaired growth hormone activity in some children with FGR who have persistent poor growth in the postnatal period.

Fetal consequences of chronic substrate deprivation

The aim of this paper is to review the mechanisms by which animal and human fetuses survive prolonged periods of substrate deprivation in utero. Two reasons why such information is important for those who care for growth-restricted fetuses and neonates are as follows. (1) Understanding the physiology is central to designing appropriate tests for determining fetal well-being. For instance, most currently available techniques for monitoring fetal well-being are actually better designed to detect acute than chronic fetal hypoxaemia. (2) There is increasing interest in the medium- and long-term consequences of fetal growth restriction on cardiovascular, neurological and lung function. As an example, the reasons why chronic oxygen deprivation may influence cerebral structure and function are discussed.

Prematurity and intrauterine growth retardation--double jeopardy?

Premature infants born with IUGR are at a several-fold increased risk for mortality and major neonatal morbidities, including RDS, BPD, ROP, and NEC. These severe complications of prematurity are intensified by the effect of suboptimal fetal growth. The possible pathophysiologic processes initiated in utero and continuing after birth have been discussed. Recently reported data suggest that IUGR is a risk factor in programming for the later development of cardiovascular diseases, hypertension, and diabetes mellitus in adult life. Experimental research related to the pathophysiology and etiology of these conditions may enable appropriate intervention directed at reducing the excess risk associated with the short- and long-term mortality and morbidity among premature SGA infants.

Abnormal retinal optic nerve morphology in young adults after intrauterine growth restriction

Intrauterine growth restriction (IUGR) is a recognized risk factor for neurologic deficits later in life. Abnormal fetal blood flow in the presence of fetal growth retardation helps to distinguish true fetal growth impairment from small but normally grown infants. The present study aimed to investigate the influence of IUGR with abnormal fetal blood flow on retinal optic nerve morphology at 18 y of age. A prospective study was performed in 19 subjects with IUGR [abnormal fetal aortic blood flow velocity; median birth weight deviation of -31% (-22 to -42%; median (range)] and in 23 subjects with a normal birth weight for gestational age [normal fetal aortic blood flow velocity; median birth weight deviation of -2% (-10 to 22%)]. All subjects were previously examined concerning minor neurologic dysfunction (MND) at 7 y of age. The ocular fundus was examined by ophthalmoscopy, and the optic nerve morphology was evaluated by digital image analysis. Decrease in neuroretinal rim area at 18 y of age was associated with increasing negative birth weight deviation (r = 0.71, p < 0.0001). The subjects with severe MND at 7 y had a reduced neuroretinal rim area [median (range), 1.57 mm(2) (1.37-1.78 mm(2))] compared with those with less severe MND [1.94 mm(2) (1.33-2.71 mm(2))] and with those with normal neurologic function [2.18 mm(2) (1.75-2.70 mm(2)); p < 0.05 and p < 0.0001, respectively]. A decrease in neuroretinal rim area reflects either a reduction in axonal volume or a decrease in the number of axons in the optic nerve. It is yet unclear whether this finding represents neuronal changes within other cerebral regions in subjects with IUGR.

Fetal adaptation to stress. Part I: acceleration of fetal maturation and earlier birth triggered by placental insufficiency in humans

This review is an attempt to provide an integrative view for the biological changes triggered by fetal stress through a multidisciplinary approach. Acceleration of brain and lung maturation in certain risk pregnancies was first described clinically and confirmed by biochemical, electrophysiological and experimental data. Moreover, new experimental findings suggest that a fetal clock centrally mediated by fetal nutritional status could determine timing of parturition. However, some skepticism persisted about the usefulness of this body of knowledge for obstetrical management in developed countries. The interest concerning this adaptation to intrauterine stress was later renewed from various sources, as developed in Part II.

Neuromaturation of multiples

Etiology of preterm birth and degree of maturation are the primary determinants of a preterm infant's survival and complications. Multiple gestation increases the likelihood of preterm birth but its influence on rate of maturation or complications of prematurity has been controversial, primarily because of confounding variables (e.g. race, aetiology of preterm delivery, degree of prematurity and pregnancy complications). Very low birthweight preterm multiples have virtually the same rates of neonatal mortality, complications and neuromaturation as preterm singletons of the same gestational age. There is no advantage of delivering twins or higher order multiples before 30 weeks gestation, unless a fetus decompensates in utero. Survival improves for near term intermediate-size preterm multiples while intrauterine growth decelerates and placental and fetal neuromaturation accelerate. These data and the high fetal death rate at term support delivery of multiples as soon as there is fetal lung maturity, and consideration of elective delivery of twins at 35-38 weeks gestation and triplets at 33-35 weeks gestation.

Antenatal prediction of intraventricular hemorrhage in fetal growth restriction: what is the role of Doppler?

OBJECTIVE

To evaluate relationships between neonatal intraventricular hemorrhage and altered brain blood flow in preterm growth-restricted fetuses.

METHODS

One hundred and thirteen growth-restricted fetuses (birth weight < 10th centile and umbilical artery pulsatility index > two standard deviations above gestational age mean) which delivered prematurely (< 34.0 weeks) were studied. Three expressions of altered brain blood flow were defined: 'brain sparing'= middle cerebral artery pulsatility index > two standard deviations below the gestational age mean, 'centralization' = ratio of middle cerebral artery/umbilical artery pulsatility indices (cerebroplacental ratio) > two standard deviations below the gestational age mean, and 'redistribution' = absent or reversed umbilical artery end-diastolic velocity. Intraventricular hemorrhage was graded after Papile (I-IV) by cranial ultrasound performed within 7 days of delivery.

RESULTS

Sixty-seven (59.3%) fetuses had brain sparing, 84 (74.3%) had centralization and 51 (45.1%) had redistribution. Fifteen (13.3%) neonates had intraventricular hemorrhage and were more likely to have a biophysical profile < 6, earlier delivery for fetal indications, lower cord artery pH, HCO3, hemoglobin, and platelets, a 10-min Apgar score < 7 and high perinatal mortality (5/15; 33.3%). No associations between intraventricular hemorrhage and brain sparing or centralization were identified. However, neonates with intraventricular hemorrhage had significantly higher umbilical artery pulsatility index deviations from the gestational age mean and a relative risk of 4.9-fold for intraventricular hemorrhage with redistribution (95% confidence interval, 1.5-16.3; P < 0.005). Multiple logistic regression revealed significant associations between intraventricular hemorrhage and a low 10-min Apgar score (r = 0.30, P < 0.005) and low hemoglobin (r = 0.28), gestational age at delivery (r = 0.25) and birth-weight centiles (r = 0.23) (P < 0.05). No Doppler parameter was identified as an independent contributor to intraventricular hemorrhage.

CONCLUSION

While loss of umbilical artery end-diastolic velocity early in gestation significantly increases the risk for neonatal intraventricular hemorrhage, prematurity and difficult transition to extrauterine life remain the most important determinants of intraventricular hemorrhage.

The discrepancy between maturation of visual-evoked potentials and cognitive outcome at five years in very preterm infants with and without hemodynamic signs of fetal brain-sparing

OBJECTIVE

After intrauterine growth restriction we found at the age of 6 months an acceleration of neurophysiologic maturation. However, at later ages impaired cognitive outcome has been reported. Therefore, we investigated in children with and without fetal hemodynamic adaptation to intrauterine growth restriction whether the accelerated neurophysiologic maturation in infancy might be associated with impaired cognitive outcome at preschool age.

DESIGN

At 5 years of age cognitive function was assessed using the Revision of the Amsterdam Children's Intelligence Test in 73 preterm infants (26-33 weeks) who were prospectively followed from the antenatal period up to the age of 5 years. Maternal educational level was used as a background variable to estimate the confounding effects of socioeconomic status on cognitive function. Fetal Doppler studies were performed and the umbilical artery pulsatility index (PI) divided by the middle cerebral artery PI ratio (U/C ratio) was calculated. A U/C ratio >0.725 was considered as an indication of fetal cerebral hemodynamic adaptation to a compromised placental perfusion, ie, fetal brain-sparing. Visual-evoked potentials (VEPs) were recorded at 6 months and 1 year of age. In addition, data on neurologic status at 3 years were available.

RESULTS

Mean IQ score was significantly lower for children born with a raised U/C ratio (87 +/- 16) compared with children with a normal U/C ratio (96 +/- 17). VEP latencies decreased significantly in infants with a normal U/C ratio, whereas no decrease was found in infants with a raised U/C ratio. Variables contributing significantly to the variance of cognitive function were: U/C group, VEP latency maturation, level of maternal education, and neurodevelopmental outcome at 3 years. The linear regression model explained 33% of the variance in cognitive function.

CONCLUSIONS

Both being born with a raised U/C ratio and an acceleration of VEP latencies are negatively associated with cognitive outcome at 5 years of age. Fetal brain-sparing, although a seemingly beneficial adaptive mechanism for intact neurologic survival, is, however, later associated with a poorer cognitive outcome.

Prediction of perinatal outcome in fetuses suspected to have intrauterine growth restriction: Doppler US study of fetal cerebral, renal, and umbilical arteries

PURPOSE

To determine and compare the diagnostic performance of fetal middle cerebral (MCA), renal (RA), and umbilical (UA) arterial Doppler ultrasonography (US) for prediction of adverse perinatal outcome in suspected intrauterine growth restriction (IUGR).

MATERIALS AND METHODS

Two hundred ninety-three small-for-gestational age fetuses (24-39 weeks at recruitment and US-estimated weight or abdominal circumference below 10th percentile) were prospectively examined with Doppler US of the UA, MCA, and RA. Clinicians were blinded to MCA and RA Doppler measurements.

RESULTS

Seventy-six fetuses (25.9%) had at least one major or minor adverse perinatal outcome. Major outcomes included stillbirth, neonatal death, neurologic complication, and necrotizing enterocolitis. The MCA pulsatility index (PI), compared with the UA PI and RA PI, was more sensitive (72.4% vs 44.7% and 8.3%) but less specific (58.1% vs 86.6% and 92.6%) in predicting adverse outcome. The UA PI had the highest positive likelihood ratio (ratio, 3.3); the MCA PI had the lowest negative likelihood ratio (ratio, 0.48). When gestational age at the first Doppler US examination was less than 32 weeks, the MCA PI had a sensitivity of 95.5% and negative predictive value of 97.7% for major adverse outcome (negative likelihood ratio, 0.10).

CONCLUSION

In suspected IUGR, while an abnormal UA PI is a better predictor of adverse perinatal outcome than an abnormal MCA or RA PI, a normal MCA PI may help to identify fetuses without major adverse perinatal outcome, especially before 32 weeks gestational age.

Consequences of fetal growth restriction

An increasing number of diseases in child and adult life are now thought to have their origins in the fetal period. Central to this predisposition is restriction of fetal growth. During the period reviewed in this article, the associations between adult hypertension and low birthweight were confirmed, and numerous studies have investigated possible mechanisms by which the metabolism of an individual may be programmed by an adverse intrauterine environment. The consequences in adult life of intrauterine undernutrition now highlight prenatal care as one of the most crucial issues in medicine and challenge many aspects of current obstetric decision-making. Research targeting fetal growth and development can be expected to result in improved health at all ages.