Cognitive outcome at 2 years of age in Finnish infants with very low birth weight born between 2001 and 2006

Does the Degree of Prematurity Relate to the Bayley-4 Scores Earned by Matched Samples of Infants and Toddlers across the Cognitive, Language, and Motor Domains?

The literature on children born prematurely has consistently shown that full-term babies outperform preterm babies by about 12 IQ points, even when tested as adolescents, and this advantage for full-term infants extends to the language and motor domains as well. The results of comprehensive meta-analyses suggest that the degree of prematurity greatly influences later test performance, but these inferences are based on data from an array of separate studies with no control of potential confounding variables such as age. This study analyzed Bayley-4 data for 66 extremely premature infants and toddlers (<32 weeks), 70 moderately premature children (32-36 weeks), and 133 full-term children. All groups were carefully matched on key background variables by the test publisher during the standardization of the Bayley-4. This investigation analyzed data on the five subtests: cognitive, expressive communication, receptive communication, fine motor, and gross motor. A multivariate analysis of covariance (MANCOVA) assessed for group mean differences across the three subsamples, while controlling for the children's age. Extremely premature children scored significantly lower than moderately premature children on all subtests, and both preterm groups were significantly outscored by the full-term sample across all domains. In each set of comparisons, the cognitive and motor subtests yielded the largest differences, whereas language development, both expressive and receptive, appeared the least impacted by prematurity. A follow-up MANOVA was conducted to examine full-term versus preterm discrepancies on the five subtests for infants (2-17 months) vs. toddlers (18-42 months). For that analysis, the two preterm groups were combined into a single preterm sample, and a significant interaction between the age level and group (full-term vs. preterm) was found. Premature infants scored lower than premature toddlers on receptive communication, fine motor, and cognitive. Neither expressive communication nor gross motor produced significant discrepancies between age groups The findings of this study enrich the preterm literature on the degree of prematurity; the age-based interactions have implications for which abilities are most likely to improve as infants grow into toddlerhood.

Altered temporal connectivity and reduced meta-state dynamism in adolescents born very preterm

Adolescents born very preterm have an increased risk for anxiety, social difficulties and inattentiveness, i.e. the 'preterm behavioural phenotype'. The extreme end of these traits comprises the core diagnostic features of attention and hyperactivity disorders and autism spectrum disorder, which have been reported to show aberrant dynamic resting-state functional network connectivity. This study aimed to compare this dynamism between adolescents born very preterm and controls. A resting-state functional magnetic resonance imaging was performed on 24 adolescents born very preterm (gestational age <32 weeks and/or birth weight ≤1500 g) and 32 controls born full term (≥37 weeks of gestation) at 13 years of age. Group-wise comparisons of dynamic connectivity between the resting-state networks were performed using both hard clustering and meta-state analysis of functional network connectivity. The very preterm group yielded a higher fraction of time spent in the least active connectivity state in hard clustering state functional network connectivity, even though no group differences in pairwise connectivity patterns were discovered. The meta-state analysis showed a decreased fluidity and dynamic range in the very preterm group compared with controls. Our results suggest that the 13-year-old adolescents born very preterm differ from controls in the temporal characteristics of functional connectivity. The findings may reflect the long-lasting effects of prematurity and the clinically acknowledged 'preterm behavioural phenotype'.

Performance in Hand Coordination Tasks and Concurrent Functional MRI Findings in 13-Year-Olds Born Very Preterm

BACKGROUND

Fine motor and coordination problems are frequently reported among adolescents born preterm. We aimed to assess performance in hand coordination tasks and to compare concurrent brain activation between adolescents born very preterm and at term at 13 years.

METHODS

A total of 34 right-handed adolescents born very preterm (gestational age less than 32 weeks/birth weight ≤1500 grams) and 37 controls born at term during 2003 to 2006 in Turku University Hospital, Finland, were recruited. At 13 years, finger opposition and diadochokinesis were assessed, and brain functional magnetic resonance imaging data were acquired while the adolescents performed unimanual hand coordination tasks in response to visual cue.

RESULTS

Adolescents born very preterm performed similar to controls in hand coordination tasks. The very preterm group evoked greater brain activation than the controls in the right precentral gyrus and in the right postcentral gyrus during left-hand finger opposition and in the right postcentral gyrus during left-hand diadochokinesis. Within the very preterm group, lower gestational age was associated with reduced activation in the left superior parietal lobule during right-hand diadochokinesis. Regarding left-hand tasks, lower gestational age was associated with stronger activation in the right cerebellar lobule V and left cerebellar lobule VI during finger opposition and stronger activation in the right superior parietal lobule during diadochokinesis.

CONCLUSIONS

Very preterm birth affected hand coordination-related brain activation. Most of the effects were found for nondominant hand. Clinical performance during the hand coordination tasks was similar in adolescents born very preterm and controls.

The impact of susceptibility correction on diffusion metrics in adolescents

BACKGROUND

Diffusion tensor imaging is a widely used imaging method of brain white matter, but it is prone to imaging artifacts. The data corrections can affect the measured values.

OBJECTIVE

To explore the impact of susceptibility correction on diffusion metrics.

MATERIALS AND METHODS

A cohort of 27 healthy adolescents (18 boys, 9 girls, mean age 12.7 years) underwent 3-T MRI, and we collected two diffusion data sets (anterior-posterior). The data were processed both with and without susceptibility artifact correction. We derived fractional anisotropy, mean diffusivity and histogram data of fiber length distribution from both the corrected and uncorrected data, which were collected from the corpus callosum, corticospinal tract and cingulum bilaterally.

RESULTS

Fractional anisotropy and mean diffusivity values significantly differed when comparing the pathways in all measured tracts. The fractional anisotropy values were lower and the mean diffusivity values higher in the susceptibility-corrected data than in the uncorrected data. We found a significant difference in total tract length in the corpus callosum and the corticospinal tract.

CONCLUSION

This study indicates that susceptibility correction has a significant effect on measured fractional anisotropy, and on mean diffusivity values and tract lengths. To receive reliable and comparable results, the correction should be used systematically.

Neuroimaging at Term Equivalent Age: Is There Value for the Preterm Infant? A Narrative Summary

Advances in neuroimaging of the preterm infant have enhanced the ability to detect brain injury. This added information has been a blessing and a curse. Neuroimaging, particularly with magnetic resonance imaging, has provided greater insight into the patterns of injury and specific vulnerabilities. It has also provided a better understanding of the microscopic and functional impacts of subtle and significant injuries. While the ability to detect injury is important and irresistible, the evidence for how these injuries link to specific long-term outcomes is less clear. In addition, the impact on parents can be profound. This narrative summary will review the history and current state of brain imaging, focusing on magnetic resonance imaging in the preterm population and the current state of the evidence for how these patterns relate to long-term outcomes.

Executive Function Profiles at Home and at School in 11-Year-Old Very Low Birth Weight or Very Low Gestational Age Children

OBJECTIVE

Executive function (EF) problems of children born at very low birth weight (VLBW; ≤1500 g) or very low gestational age (VLGA; <32 gestational weeks) may present differently at school compared to the home environment. Ecological assessment of EF including parent- and teacher-rated profiles and associated risk factors of 11-year-old children born at VLBW or VLGA was evaluated.

METHODS

A total of 125 VLBW or VLGA children and 132 controls were assessed using the Behavior Rating Inventory of EF, which includes 8 subscales that form the Behavioral Regulation and Metacognition Indexes. For VLBW or VLGA children, full-scale intelligence quotient (IQ) was assessed using the Wechsler Intelligence scale for Children, Fourth Edition. Neonatal data were collected systematically.

RESULTS

VLBW or VLGA children with full-scale IQ ≥ 70 had clinically significant problems in the Working Memory subscale at school. Although they had clinically significant problems at home in the Behavioral Regulation Index, the difference disappeared when adjusted for paternal education. Lower gestational age, lower birth weight z-score, surgical necrotizing enterocolitis, low paternal and maternal education, and lower full-scale IQ were identified to be risk factors for higher scores in ecological assessment of EF.

CONCLUSION

VLBW or VLGA children in this cohort exhibit fewer EF problems in ecological assessment of EF compared to previous literature. EF problems of this study population vary by home and school setting and are emphasized in working memory at school. Screening for EF problems in school environment is recommended to target the support.

Prenatal Risk Factors for Adverse Developmental Outcome in Preterm Infants-Systematic Review

Background: Preterm infants are still at an increased risk for suboptimal neurodevelopmental outcomes when compared with term born infants. The development of a child born preterm can be jeopardized by suboptimal conditions during pregnancy, in addition to the suboptimal growth environment postnatally compared to the normal in utero environment. This review summarizes the literature on the role of chorioamnionitis, placental insufficiency, and maternal smoking on the developmental outcomes of preterm infants. Methods: A systematic database search was performed to identify all original articles published on or before September 12, 2018 that evaluated the impact of clinical or histological chorioamnionitis, abnormal prenatal fetal and placental blood flow, and prenatal smoking exposure on the neuropsychological and cognitive outcomes of preterm infants. We identified a total of 54 studies. Thirty five original articles evaluated the effects of clinical or histological chorioamnionitis; 15 studies evaluated the effects of abnormal blood flow patterns; and four studies evaluated the effects of maternal smoking during pregnancy. Results: The studies on prenatal risk factors showed conflicting results about the impact on the neurodevelopment of preterm infants. The majority of the studies did not show that chorioamnionitis poses a direct risk to the development of preterm infants. The role of abnormal prenatal placental and fetal blood flow on the development of preterm infants remained inconclusive because the sample sizes were often small and methodological problems complicated the interpretation of the data. Maternal smoking during pregnancy was assessed only in one cohort which showed that maternal smoking is a risk for suboptimal cognitive and neuropsychological development in preterm infants. Conclusions: This review summarizes the data on several prenatal risk factors which play a role in the developmental outcomes of preterm infants. To optimize the developmental outcomes, we need to first optimize the fetal wellbeing before birth. More research that extends from the fetal life to long-term developmental outcomes is needed.

Factors affecting the cognitive profile of 11-year-old children born very preterm

BackgroundPreterm birth is a risk for cognitive development. This study assessed the cognitive profile of children born very preterm at the age of 11 years as well as the associated risk factors.MethodsA total of 128 children born very preterm were included. Magnetic resonance imaging was performed at term age. Cognitive development was assessed using the full-scale intelligence quotient (IQ) and four domains of the Wechsler Intelligence Scale for Children, fourth edition (WISC-IV), Finnish translation. The results were compared with test norms.ResultsMost study children performed at average (51%) or low average (21%) levels in the full-scale IQ assessment. The correlation between 5- and 11-year full-scale IQ was 0.73 (P<0.001). Compared with the normative data, children born very preterm performed poorer in all domains of the cognitive profile. The only significant risk factor for poor general cognition was major brain pathology. When considering all four domains of WISC-IV, low paternal education, male gender, and low birth weight z score were also found to be significant risk factors.ConclusionsLess than one-third of the children born very preterm performed below the low average cognitive level at 11 years of age. Specific neonatal and sociodemographic risk factors were identified as affecting the cognitive profile.

Brain injury in the international multicenter randomized SafeBoosC phase II feasibility trial: cranial ultrasound and magnetic resonance imaging assessments

BACKGROUND

Abnormal cerebral perfusion during the first days of life in preterm infants is associated with higher grades of intraventricular hemorrhages and lower developmental score. In SafeBoosC II, we obtained a significant reduction of cerebral hypoxia by monitoring cerebral oxygenation in combination with a treatment guideline. Here, we describe (i) difference in brain injury between groups, (ii) feasibility of serial cranial ultrasound (cUS) and magnetic resonance imaging (MRI), (iii) local and central cUS assessment.

METHODS

Hundred and sixty-six extremely preterm infants were included. cUS was scheduled for day 1, 4, 7, 14, and 35 and at term-equivalent age (TEA). cUS was assessed locally (unblinded) and centrally (blinded). MRI at TEA was assessed centrally (blinded). Brain injury classification: no, mild/moderate, or severe.

RESULTS

Severe brain injury did not differ significantly between groups: cUS (experimental 10/80, control 18/77, P = 0.32) and MRI (5/46 vs. 3/38, P = 0.72). Kappa values for local and central readers were moderate-to-good for severe and poor-to-moderate for mild/moderate injuries. At TEA, cUS and MRI were assessed in 72 and 64%, respectively.

CONCLUSION

There was no difference in severe brain injury between groups. Acquiring cUS and MRI according the standard operating procedures must be improved for future trials. Whether monitoring cerebral oxygenation during the first 72 h of life prevents brain injury should be evaluated in larger multicenter trials.

Contributions of a Child's Built, Natural, and Social Environments to Their General Cognitive Ability: A Systematic Scoping Review

The etiology of a child’s cognitive ability is complex, with research suggesting that it is not attributed to a single determinant or even a defined period of exposure. Rather, cognitive development is the product of cumulative interactions with the environment, both negative and positive, over the life course. The aim of this systematic scoping review was to collate evidence associated with children’s cognitive health, including inherent factors as well as chemical and non-chemical stressors from the built, natural, and social environments. Three databases were used to identify recent epidemiological studies (2003–2013) that examined exposure factors associated with general cognitive ability in children. Over 100 factors were evaluated from 258 eligible studies. We found that recent literature mainly assessed the hypothesized negative effects of either inherent factors or chemical exposures present in the physical environment. Prenatal growth, sleep health, lead and water pollutants showed consistent negative effects. Of the few studies that examined social stressors, results consistently showed cognitive development to be influenced by both positive and negative social interactions at home, in school or the community. Among behavioral factors related to diet and lifestyle choices of the mother, breastfeeding was the most studied, showing consistent positive associations with cognitive ability. There were mostly inconsistent results for both chemical and non-chemical stressors. The majority of studies utilized traditional exposure assessments, evaluating chemical and non-chemical stressors separately. Collective evidence from a limited number of studies revealed that cumulative exposure assessment that incorporates multiple chemical and non-chemical stressors over the life course may unravel the variability in effect on cognitive development and help explain the inconsistencies across studies. Future research examining the interactions of multiple stressors within a child’s total environment, depicting a more real-world exposure, will aid in understanding the cumulative effects associated with a child’s ability to learn.

Predicting developmental outcomes in premature infants by term equivalent MRI: systematic review and meta-analysis

BACKGROUND

This study aims to determine the prognostic accuracy of term MRI in very preterm born (≤32 weeks) or low-birth-weight (≤1500 g) infants for long-term (>18 months) developmental outcomes.

METHODS

We performed a systematic review searching Central, Medline, Embase, and PsycInfo. Two independent reviewers performed study selection, data extraction, and quality assessment. We documented sensitivity and specificity for three different MRI findings (white matter abnormalities (WMA), brain abnormality (BA), and diffuse excessive high signal intensity (DEHSI)), related to developmental outcomes including cerebral palsy (CP), visual and/or hearing problems, motor, neurocognitive, and behavioral function. Using bivariate meta-analysis, we estimated pooled sensitivity and specificity and plotted summary receiver operating characteristic (sROC) curves for different cut-offs of MRI.

RESULTS

We included 20 papers published between 2000 and 2013. Quality of included studies varied. Pooled sensitivity and specificity values (95 % confidence interval (CI)) for prediction of CP combining the three different MRI findings (using normal/mild vs. moderate/severe cut-off) were 77 % (53 to 91 %) and 79 % (51 to 93 %), respectively. For prediction of motor function, the values were 72 % (52 to 86 %) and 62 % (29 to 87 %), respectively. Prognostic accuracy for visual and/or hearing problems, neurocognitive, and/or behavioral function was poor. sROC curves of the individual MRI findings showed that presence of WMA provided the best prognostic accuracy whereas DEHSI did not show any potential prognostic accuracy.

CONCLUSIONS

This study shows that presence of moderate/severe WMA on MRI around term equivalent age can predict CP and motor function in very preterm or low-birth-weight infants with moderate sensitivity and specificity. Its ability to predict other long-term outcomes such as neurocognitive and behavioral impairments is limited. Also, other white matter related tests as BA and DEHSI demonstrated limited prognostic value.

SYSTEMATIC REVIEW REGISTRATION

PROSPERO CRD42013006362.

Extremely preterm birth affects boys more and socio-economic and neonatal variables pose sex-specific risks

AIM

The early identification of at-risk extremely preterm (EPT) children could improve long-term outcomes. This study sought to investigate sex differences in developmental outcomes and to identify sex-specific predictors at two and a half years of age.

METHODS

We assessed 217 boys and 181 girls born before 27-week gestation using the Bayley Scales of Infant and Toddler Development, third edition (Bayley-III), as a part of the Extremely Preterm Infants in Sweden Study. Sex-specific differences were calculated. Socio-economic, birth and neonatal factors were calculated separately for boys and girls using regression models.

RESULTS

Girls scored significantly higher than boys on all Bayley-III indices. In both sexes, brain injury, long-term ventilator treatment and foreign-born mothers predicted lower scores. Receiving breast milk by hospital discharge predicted higher scores. Severe retinopathy of prematurity was the strongest predictor of cognitive and language deficits in boys. High parental education predicted higher cognitive and language scores in girls, whereas severe bronchopulmonary dysplasia was the strongest predictor of motor deficits.

CONCLUSION

Extreme prematurity seems to affect boys more than girls. Socio-economic and neonatal factors confer similar risks or protections on both sexes, but some variables pose sex-specific risks. An awareness of risk factors may provide the basis for treatment and follow-up guidelines.

Preterm small-for-gestational age children: predictive role of gestational age for mental development at the age of 2 years

AIM

The aim of the study was to compare the cognitive development of very low birth weight (VLBW) preterm SGA children and preterm AGA children at the age of 2 years. The hypothesis was that SGA children are at an additional risk for deficits in cognitive function. Additionally, the impact of neonatal risk factors and the parents' profession on the early cognitive development was analysed.

METHODS

Cognitive function of 107 preterm infants with a gestational age of 24-35 weeks was assessed with the Mental Bayley Scales of Infant Development at the age of 2 years (mean±SEM). The results of SGA (n=38) and AGA (n=69) children were compared as well as neonatal risk factors and parental education.

RESULTS

There was a linear regression between the Mental Bayley Scales result and gestational age for preterm infants with a gestational age of 24-32 weeks. SGA and AGA children did not differ significantly in their cognitive function at the age of 2 years. A strong association was found between the parents' profession and cognitive development. Among the neonatal risk factors, bronchopulmonary dysplasia was a strong predictor of mental development.

INTERPRETATION

Cognitive development of two-year-old preterm children with a gestational age of 24-32 weeks was mainly related to their gestational age. Being born preterm and small for gestational age was not additionally associated with cognitive deficits at the age of 2 years. The parents' profession had a significant impact on the cognitive development. The role of the parents' profession on the early development of preterm infants should be elucidated in further studies.

The development and predictive value of gestures in very-low-birth-weight children: a longitudinal study

The present study analysed the development of gestures between 0;9-1;3 years, and the predictive value of this development for language skills at 2;0 in very-low-birth-weight (VLBW) children. Participants were 32 VLBW children and their 35 controls. The data on gestures was gathered using the Finnish version of the Communicative Development Inventory (FinCDI). At 2;0, the language skills of the children were assessed using the Reynell Developmental Language Scales (RDLS III) and the FinCDI. The number of acquired gestures was lower in the VLBW children than in the controls. The development of gestures correlated significantly with later expressive language in both groups, but significant correlations between the development of gestures and later receptive language development were detected only in the VLBW group. When the predictive value of gestures and early expressive and receptive lexicon with regard to later language skills were analysed, the development of gestures at 1;3 had good predictive value for poor language performance at 2;0. In addition, a small receptive lexicon size at 1;0 and at 1;3 was also a good predictor for later language performance. The development of gestures and receptive lexicon thus jointly provide clinically valuable information on the emerging language skills of VLBW children.

The role of neuroimaging in predicting neurodevelopmental outcomes of preterm neonates

Magnetic resonance imaging (MRI) is a safe and high-resolution neuroimaging modality that is increasingly used in the neonatal population to assess brain injury and its consequences on brain development. It is superior to cranial ultrasound for the definition of patterns of both white and gray matter maturation and injury and therefore has the potential to provide prognostic information on the neurodevelopmental outcomes of the preterm population. Furthermore, the development of sophisticated MRI strategies, including diffusion tensor imaging, resting state functional connectivity, and magnetic resonance spectroscopy, may increase the prognostic value, helping to guide parental counseling and allocate early intervention services.

Taiwanese parents' perceptions of their very low-birth-weight infant with developmental disabilities

This study explores the perceptions and experiences of Taiwanese parents in coping with the unfolding evidence of a disability, their response to the official diagnosis, and their views about their child's developmental disability. This descriptive qualitative study is a partial analysis of data from a larger study including 19 Taiwanese parents of very low-birth-weight infants with developmental disability at 6 and 12 months of corrected age. Four themes were generated: uncertainty and worry about developmental progress, search for meaning and supernatural will, desire for normality and attitude toward services, and finding a balance point in family life and relationships. The parents of very low-birth-weight infants face uncertainty about developmental and other potential problems in the infant's early age. Adequate information related to infant development needs to be integrated into follow-up clinic and early intervention services. Early intervention programs should not only focus on the needs of these infants but also provide support and care to the whole family. Understanding parental beliefs and values toward developmental disabilities can help neonatal and pediatric professionals to provide optimal early intervention to these families.

A history of low birth weight alters recovery following a future head injury: a case series

OBJECTIVE

Low birth weight (LBW; below 2500 grams) is a general risk factor for a variety of neurodevelopmental difficulties. However, these children may remain more vulnerable to neurologic and environmental insults occurring years later. This prospective case series reports on children who sustained a mild, moderate, or severe traumatic brain injury (TBI) in middle childhood but who had also been born with birth weights below 2500 grams.

PARTICIPANTS

PARTICIPANTS were 14 children with mild, moderate, or severe traumatic brain injury (TBI), 5 of whom had birth weights under 2500 grams (LBW) and 9 children with normal birth weight (NBW). All participants were drawn from a larger study on the long-term cognitive and behavioral impact of pediatric TBI and were matched on age, estimated socioeconomic status (SES), and severity of TBI (with NBW children actually having a slightly worse overall injury severity).

RESULTS

At baseline, both groups exhibited similar scores on WJ-R Letter Word Identification and Calculations, Tower of London number solved, and CVLT-C total correct. Baseline group differences were observed on the CELF-III Formulated Sentences (NBW > LBW) and on the VABS Adaptive Behavior Composite and Socialization subdomain (LBW > NBW). Over 2 years, relative to the NBW group, the LBW group evidenced declines on both WJ-R subtests, CVLT-C total correct, CELF-III Formulated Sentences, and VABS Adaptive Behavior Composite and Socialization.

CONCLUSIONS

Although preliminary in nature due to small sample size, findings suggest a history of LBW influences the recovery trajectory following childhood TBI. Academic and adaptive functioning and verbal memory appeared particularly affected.

Imaging the premature brain: ultrasound or MRI?

Neuroimaging of preterm infants has become part of routine clinical care, but the question is often raised on how often cranial ultrasound should be done and whether every high risk preterm infant should at least have one MRI during the neonatal period. An increasing number of centres perform an MRI either at discharge or around term equivalent age, and a few centres have access to a magnet in or adjacent to the neonatal intensive care unit and are doing sequential MRIs. In this review, we try to discuss when best to perform these two neuroimaging techniques and the additional information each technique may provide.

[Outcome at two years corrected age of a cohort of very low birth weight infants from hospitals within the neonatal SEN1500 network]

OBJECTIVE

To describe growth and neurodevelopmental status of 4,944 children who completed a follow-up at two years of corrected age out of the 10,456 newborns with weight ≤1500g born between the years 2002-2007 and discharged from hospitals within the network SEN1500. A total of 522 newborns were excluded as they had some type of malformation. The total number of children assessed represents the 49.76% of children discharged alive and without malformations.

METHODS

A retrospective review was conducted using prospectively collected data in the SEN1500 database. We compared growth data at two years of corrected age according to birth weight and sex. Motor impairment, incidence of cerebral palsy, visual and hearing disabilities, and abnormal neurodevelopment for gestational age were analysed between groups. We studied the associations between cerebral palsy (CP) and perinatal factors.

RESULTS

At 2 years of age 44.2% of children had a weight <2 SD for corrected age. Children with birth weight ≤1000g showed worse outcomes in growth. Some type of motor impairment was observed in 6.96% of the infants, and 4.56% of them were diagnosed with CP. The incidence was higher among males with birth weight ≤1000g. There was an incidence of 5.21% of visual disability, with 0.5% of children being blind in one or both eyes. Cerebral palsy was associated with retinopathy of prematurity, severe intraventricular haemorrhage, and periventricular leukomalacia, in particular cystic periventricular leukomalacia.

Optimal timing of cerebral MRI in preterm infants to predict long-term neurodevelopmental outcome: a systematic review

SUMMARY

Advances in neonatal neuroimaging have improved detection of preterm brain injury responsible for abnormal neuromotor and cognitive development. Increasingly sophisticated MR imaging setups allow scanning during early preterm life. In this review, we investigated how brain MR imaging in preterm infants should be timed to best predict long-term outcome. Given the strong evidence that structural brain abnormalities are related to long-term neurodevelopment, MR imaging should preferably be performed at term-equivalent age. Early MR imaging is promising because it can guide early intervention studies and is indispensable in research on preterm brain injury.

Predictive value of neonatal brain MRI on the neurodevelopmental outcome of preterm infants by 5 years of age

AIM

To study the prognostic value of MRI in preterm infants at term equivalent age for cognitive development at 5 years of age.

METHODS

A total of 217 very low birth weight/very low gestational age infants who all received brain MRI at term equivalent age were categorized into 4 groups based on the brain MRI findings. Cognitive development was assessed at 5 years of chronological age by using a short form of Wechsler Preschool and Primary Scale of Intelligence - Revised. This information was combined with neurosensory diagnoses by 2 years of corrected age.

RESULTS

Of all infants 31 (17.0%) had Full Scale Intelligence Quotient (FSIQ) <85, 14 (6.5%) had cerebral palsy and 4 (1.8%) had severe hearing impairment. A total of 41 (22.0%) infants had some neurodevelopmental impairment at 5 years of age. Considering cognitive outcome (FSIQ <85), the positive predictive value of several major MRI pathologies was 43.8%, and the negative predictive value of normal finding or minor pathologies was 92.0% and 85.7%, respectively.

CONCLUSION

The MRI of the brain at term equivalent age may be valuable in predicting neurodevelopmental outcome in preterm infants by 5 years of age. The findings should always be interpreted alongside the clinical information of the infant. Furthermore, MRI should not replace a long-term clinical follow-up for very preterm infants.

Apolipoprotein E, brain injury and neurodevelopmental outcome of children

Apolipoprotein E plays an important role in neurodegenerative processes in adulthood, whereas its neurodevelopmental role is uncertain. We aimed to study the effect of apolipoprotein E on neurodevelopment in a cohort liable to neurodevelopmental changes. The cohort consisted of very preterm (<32 gestational weeks) and/or very low birth weight (<1500 g) children, and the longitudinal follow-up protocol included sequential cranial ultrasounds during infancy, brain magnetic resonance imaging at term-equivalent age, neurological and cognitive assessment (Mental Developmental Index) at the corrected age of 2 years and cognitive and neuropsychological assessments (Wechsler Preschool and Primary Scale of Intelligence and Developmental NEuroPSYchological Assessment) at the chronological age of 5 years. Apolipoprotein E genotypes were determined from 322 children. Ultrasound and magnetic resonance imaging data were available for 321 (99.7%) and 151 (46.9%) children, respectively. Neurodevelopmental assessment data were available for 138 (42.9%) to 171 (53.1%) children. Abnormal findings in ultrasounds and magnetic resonance imaging were found in 163 (50.8%) and 64 (42.4%) children, respectively. Mild cognitive delay at the corrected age of 2 years and the chronological age of 5 years was suspected in 21 (12.3%) of 171 and 19 (13.8%) of 138 children, respectively. In the Developmental NEuroPSYchological Assessment, 47 (32.6%) of 144 children had significantly impaired performances in more than one study subtest. No associations between the apolipoprotein E genotypes and imaging findings or measured neurodevelopmental variables were found. Apolipoprotein E genotypes do not appear to have major impact on brain vulnerability or neurodevelopment in children.

Follow-up study of 2-year-olds born at very low gestational age in Estonia

AIM

To study very low gestational age (VLGA, <32 weeks) infants at 2 years of age and to identify the predictors of adverse outcomes.

METHODS

A population-based cohort of 155 surviving VLGA infants born in Estonia in 2007 was followed up and compared with a matched full-term (FT) control group. A logistic regression model was used to test associations between risk factors and adverse outcomes.

RESULTS

No impairment was found in 60% of the VLGA infants. Neurodevelopmental impairment was noted in 12% of VLGA infants, with 8% of the infants affected by cerebral palsy without independent walking, 5% with cognitive delay, 10% with language delay and 1% with hearing impairment. The differences between preterm and FT infants in terms of the mean Cognitive, Language, and Motor Composite Scores assessed using the Bayley-III scales were in excess of 0.5 SD. Somatic growth delay was a significant problem among preterm infants. The existence of severe neonatal cerebral lesions was the most significant predictor of adverse outcomes.

CONCLUSION

In all domains studied, adverse conditions were more prevalent among VLGA infants than among the FT control group. Efforts to reduce neonatal morbidity in preterm infants should be a key priority for health care in Estonia.

Expression and function of ferroportin 1 in O-2A progenitor cells

Iron plays a crucial role in the survival, differentiation, and myelin formation of oligodendrocyte lineages. However, the regulation mechanism of iron homeostasis in oligodendrocytes remains unclear. Recently, much research has focused on Ferroportin 1 (FPN1), an iron exporter protein. First, about 95% pure primary rat O-2A progenitor cells were obtained by shaking methods in our laboratory. The expression of FPN1 mRNA and protein in O-2A progenitor cells were determined by reverse transcription-PCR and western blot. In addition, the localization of FPN1 at the cell membrane, in the cytoplasm and in processes was assayed by double-labeling immunofluorescence. A time-dependent increase of iron efflux from O-2A progenitor cells was confirmed by the calcein-indicated iron efflux assay. However, the same cells treated with FPN1 antibody showed no obvious change in iron release. For further confirmation, overexpression of FPN1 in O-2A progenitor cells was transduced with lentivirus. The release of iron in O-2A progenitor cells was dramatically increased by the overexpressed FPN1 when compared with that of the control group. Both ferritin (Ft) and transferrin receptor (TfR) are routinely used as indicators of labile iron pool. Cells pretreated with FPN1 antibody upregulated Ft and downregulated TfR protein level, while the opposite results occurred in the FPN1 overexpressing cells. Determination of Ft and TfR indirectly indicated that FPN1 might contribute to iron release from O-2A progenitor cells. We suggested that expression of FPN1 in O-2A progenitor cells might play a critical role in iron efflux from these cells.

Cognitive development in very vs. moderately to late preterm and full-term children: can effortful control account for group differences in toddlerhood?

BACKGROUND

Preterm birth is thought to have an adverse impact on cognitive development and self-regulation.

AIM

Examining the effect of very vs. moderately to late premature birth on cognitive development and effortful control, as well as evaluating whether effortful control explains the link between preterm birth and poorer cognitive development.

SUBJECTS

Fifty-eight very preterm children (<32 weeks gestation or <1500 g birth weight), 88 moderately to late preterm children (≥32 weeks gestation and ≥1500 birth weight) and 86 full-term children (≥38 weeks gestation and ≥2500 g birth weight) were examined at the corrected age of 24 months.

OUTCOME MEASURES

Observational and parent-report measures of effortful control as well as the Bayley Scales of Infant Development II (BSID II, Mental Scale) as a measurement of cognitive development were analyzed.

RESULTS

Very preterm and moderately to late preterm children showed significantly lower cognitive performance compared to full-term children. Lower effortful control scores (on observational measures, but not on parent-reports) were merely found for very preterm children compared to full-term children. Observational measures of effortful control partially mediated the effects of very preterm birth on cognitive performance, but did not explain the effects of moderately to late preterm birth on cognitive performance.

CONCLUSION

Preterm birth in general is related to poorer cognitive performance in toddlerhood. In addition, effortful control mediates the effects of very preterm birth on cognitive development. Findings suggest that different mechanisms link moderately to late premature birth to poor cognitive development.

Parental psychological well-being and behavioral outcome of very low birth weight infants at 3 years

OBJECTIVE

The purpose was to explore whether poor parental psychological well-being is associated with behavioral problems of very low birth weight (VLBW, ≤1500 g) infants at 3 years of age.

METHODS

In this prospective cohort study, 189 VLBW preterm infants born between January 2001 and December 2006 at the Turku University Hospital, Finland, were followed. Validated questionnaires (Beck Depression Inventory, Parenting Stress Index, and Sense of Coherence Scale) were mailed to the parents when their children were 2 years corrected age. A total of 140 parents evaluated the behavior of the child at 3 years by filling out the Child Behavior Checklist.

RESULTS

There were significant associations between most of the measures of parental symptoms of depression, parenting stress, and sense of coherence and the behavioral outcome of the VLBW infants. The concomitant symptoms of both parents were associated with more problematic child behavior.

CONCLUSIONS

Parents report more behavioral and emotional problems in VLBW children at age 3 if they themselves have had symptoms of depression, parenting stress, or weak sense of coherence 1 year earlier. The new finding of this study was to show the significance of the father's psychological well-being on the behavioral development of a preterm child.

Stability of cognitive outcome from 2 to 5 years of age in very low birth weight children

OBJECTIVES

This study assessed the stability of cognitive outcomes of premature, very low birth weight (VLBW; ≤1500 g) children.

METHODS

A regional cohort of 120 VLBW children born between 2001 and 2004 was followed up by using the Bayley Scales of Infant Development, Second Edition, at 2 years of corrected age and the Wechsler Preschool and Primary Scale of Intelligence-Revised at the age of 5 years. The Mental Development Index (MDI) and the full-scale IQ (FSIQ) were measured, respectively. A total of 168 randomly selected healthy term control children born in the same hospital were assessed for MDI and FSIQ.

RESULTS

In the VLBW group, mean ± SD MDI was 101.2 ± 16.3 (range: 50-128), mean FSIQ was 99.3 ± 17.7 (range: 39-132), and the correlation between MDI and FSIQ was 0.563 (P < .0001). In the term group, mean MDI was 109.8 ± 11.7 (range: 54-128), mean FSIQ was 111.7 ± 14.5 (range: 73-150), and the correlation between MDI and FSIQ was 0.400 (P < .0001). Overall, 83% of those VLBW children who had significant delay (-2 SD or less) according to MDI had it also in FSIQ. Similarly, 87% of those children who were in the average range in MDI were within the average range in FSIQ as well.

CONCLUSIONS

Good stability of cognitive development over time was found in VLBW children and in term children between the ages of 2 and 5 years. This conclusion stresses the value and clinical significance of early assessment at 2 years of corrected age. However, we also emphasize the importance of a long-term follow-up covering a detailed neuropsychological profile of these at-risk children.

Developmental outcome of very low birth weight infants in a developing country

Background

Advances in neonatal care allow survival of extremely premature infants, who are at risk of handicap. Neurodevelopmental follow up of these infants is an essential part of ongoing evaluation of neonatal care. The neonatal care in resource limited developing countries is very different to that in first world settings. Follow up data from developing countries is essential; it is not appropriate to extrapolate data from units in developed countries. This study provides follow up data on a population of very low birth weight (VLBW) infants in Johannesburg, South Africa.

Methods

The study sample included all VLBW infants born between 01/06/2006 and 28/02/2007 and discharged from the neonatal unit at Charlotte Maxeke Johannesburg Academic Hospital (CMJAH). Bayley Scales of Infant and Toddler Development Version 111 (BSID) 111 were done to assess development. Regression analysis was done to determine factors associated with poor outcome.

Results

178 infants were discharged, 26 were not available for follow up, 9 of the remaining 152 (5.9%) died before an assessment was done; 106 of the remaining 143 (74.1%) had a BSID 111 assessment. These 106 patients form the study sample; mean birth weight and mean gestational age was 1182 grams (SD: 197.78) and 30.81 weeks (SD: 2.67) respectively. The BSID (111) was done at a median age of 16.48 months. The mean cognitive subscale was 88.6 (95% CI: 85.69 - 91.59), 9 (8.5%) were < 70, mean language subscale was 87.71 (95% CI: 84.85 - 90.56), 10 (9.4%) < 70, and mean motor subscale was 90.05 (95% CI: 87.0 - 93.11), 8 (7.6%) < 70. Approximately one third of infants were identified as being at risk (score between 70 and 85) on each subscale. Cerebral palsy was diagnosed in 4 (3.7%) of babies. Factors associated with poor outcome included cystic periventricular leukomalacia (PVL), resuscitation at birth, maternal parity, prolonged hospitalisation and duration of supplemental oxygen. PVL was associated with poor outcome on all three subscales. Birth weight and gestational age were not predictive of neurodevelopmental outcome.

Conclusion

Although the neurodevelopmental outcome of this group of VLBW infants was within the normal range, with a low incidence of cerebral palsy, these results may reflect the low survival of babies with a birth weight below 900 grams. In addition, mean subscale scores were low and one third of the babies were identified as "at risk", indicating that this group of babies warrants long-term follow up into school going age.

Development of smooth pursuit eye movements in very preterm born infants: 3. Association with perinatal risk factors

AIM

To investigate the association between perinatal risk factors and neonatal complications and early oculo-motor development in very preterm infants.

METHODS

Perinatal risk factors were identified, and the potential association with early oculo-motor development was evaluated by measuring smooth pursuit eye movements (SP) at 2 and 4 months' corrected age (CA) in a population of very preterm infants born in Uppsala County 2004-2007 (n = 113).

RESULTS

Among the 15 tested factors, eight showed significant association in univariate analysis with lower levels of SP at 4 months' CA, namely administration of prenatal corticosteroids, gestational age, birthweight, bronchopulmonary dysplasia, retinopathy of prematurity, periventricular leukomalacia, intraventricular haemorrhage >grade 2, and persistent ductus arteriosus. At 2 months' CA, only retinopathy of prematurity >stage 2 was associated with lower levels of SP. When all factors significant in the univariate tests were included in multiple regressions aimed to assess each factor's independent relation to SP, periventricular leukomalacia was the only significant independent factor. When adding 2-5 of the significant factors using multiple regression analysis, the levels of SP became lower.

CONCLUSION

Perinatal risk factors were associated with lower levels of SP. This could be interpreted as delayed or disturbed development of normal oculomotor ability.

Neuroimaging biomarkers of preterm brain injury: toward developing the preterm connectome

For typically developing infants, the last trimester of fetal development extending into the first post-natal months is a period of rapid brain development. Infants who are born premature face significant risk of brain injury (e.g., intraventricular or germinal matrix hemorrhage and periventricular leukomalacia) from complications in the perinatal period and also potential long-term neurodevelopmental disabilities because these early injuries can interrupt normal brain maturation. Neuroimaging has played an important role in the diagnosis and management of the preterm infant. Both cranial US and conventional MRI techniques are useful in diagnostic and prognostic evaluation of preterm brain development and injury. Cranial US is highly sensitive for intraventricular hemorrhage (IVH) and provides prognostic information regarding cerebral palsy. Data are limited regarding the utility of MRI as a routine screening instrument for brain injury for all preterm infants. However, MRI might provide diagnostic or prognostic information regarding PVL and other types of preterm brain injury in the setting of specific clinical indications and risk factors. Further development of advanced MR techniques like volumetric MR imaging, diffusion tensor imaging, metabolic imaging (MR spectroscopy) and functional connectivity are necessary to provide additional insight into the molecular, cellular and systems processes that underlie brain development and outcome in the preterm infant. The adult concept of the "connectome" is also relevant in understanding brain networks that underlie the preterm brain. Knowledge of the preterm connectome will provide a framework for understanding preterm brain function and dysfunction, and potentially even a roadmap for brain plasticity. By combining conventional imaging techniques with more advanced techniques, neuroimaging findings will likely be used not only as diagnostic and prognostic tools, but also as biomarkers for long-term neurodevelopmental outcomes, instruments to assess the efficacy of neuroprotective agents and maneuvers in the NICU, and as screening instruments to appropriately select infants for longitudinal developmental interventions.

Outcomes of very-low-birthweight infants at 3 years of age born in 2003-2004 in Japan

BACKGROUND

The aim of this study was to describe and compare neurodevelopmental outcomes with birthweight (BW) groups at 250-g intervals of very-low-birthweight (VLBW) infants at 3 years of age in a multicenter cohort in Japan.

METHODS

A total of 3104 VLBW infants born in 2003 and 2004 registered in a NICU-network database were followed in the study. Neurodevelopmental impairment (NDI) was defined as any of the following impairments: cerebral palsy, unilateral or bilateral blindness, severe hearing impairment, or developmental delay; a developmental quotient (DQ) <70 measured using the Kyoto Scale of Psychological Development test or judged by physicians in infants without the test.

RESULTS

A total of 257 infants died and follow-up data were obtained from 1826 infants. Of the 1826 infants, 155 (8.5%) had cerebral palsy, 25 (1.4%) had visual impairment, and 12 (0.7%) had hearing impairment. Of the 1197 infants in whom DQ was measured, 184 (15.4%) had DQ < 70. The proportion of NDI in the evaluated infants was 19.2% (n= 350), ranging from 11.9% (BW 1251-1500 g) to 42.0% (BW ≤ 500 g). Odds ratios (95%CI) of NDI or death against the group BW 1251-1500 g were 20.62 (13.29-31.97) in BW ≤ 500 g, 7.25 (5.45-9.64) in BW 501-750 g, 2.85 (2.12-3.82) in BW 751-1000 g and 1.18 (0.85-1.64) in BW 1001-1250 g.

CONCLUSION

The increasing proportion of NDI or death, an indicator of adverse outcome, was associated with decrement in the BW of the groups. Although we have to consider a bias due to loss of follow-up data, the incidence of NDI was similar to previous overseas cohort studies despite the higher survival proportion in our study.

Parental psychological well-being and cognitive development of very low birth weight infants at 2 years

AIM

To assess the associations between cognitive development of very low birth weight (VLBW) infants and measures of parental psychological well-being.

METHODS

In this prospective cohort study, 182 VLBW infants born 1/2001-12/2006 at the Turku University Hospital, Finland, were followed up. At 2 years corrected age, cognitive development of the child was assessed using the Mental Development Index of Bayley Scales, and both parents filled in validated questionnaires defining parental psychological well-being (Beck Depression Inventory, Parenting Stress Index and Sense of Coherence Scale).

RESULTS

The cognitive delay of the infant was associated with paternal symptoms of depression (p = 0.007) and parenting stress (p = 0.03). Mothers of the infants with cognitive delay reported increased parenting stress related to the difficulty to accept the child (p = 0.001). Weak sense of coherence predicted depressive symptoms in both parents (p < 0.0001).

CONCLUSION

Even if the fathers of VLBW infants experienced depressive symptoms less often than the mothers, the ability of the fathers to cope was significantly associated with the cognitive development of the infant. In addition, the fathers reported more parenting stress if the infant had a cognitive delay. The mothers reported more parenting stress related to accepting the VLBW infant with cognitive delay.

Neurodevelopmental outcomes in very low-birth-weight infants in Korea: 1998-2007 vs 1989-1997

The authors reviewed the medical records of very low-birth-weight infants admitted from 1998 to 2007 and compared neurodevelopmental outcomes with their previously reported data from 1989 to 1997. The recent group included 824 infants, and the previous group included 471 infants. Neurodevelopmental outcomes were classified into cerebral palsy and non-cerebral palsy neurodevelopmental impairment. In the recent group, the survival rate was significantly higher (79.4% vs 66.2%), the rate of cerebral palsy was lower (7.9% vs 10.5%), and the rate of non-cerebral palsy neurodevelopmental impairment was higher (6.0% vs 4.5%) but not significant. The survival rate increased significantly over time, but there was no significant change in neurodevelopmental outcomes over time. Multivariate analysis indicated that abnormal neurosonographic findings, using assisted ventilation, vaginal delivery, and abnormal brainstem auditory evoked potential, were associated with increased risk for cerebral palsy.

Reprint of "The developing oligodendrocyte: key cellular target in brain injury in the premature infant"

Brain injury in the premature infant, a problem of enormous importance, is associated with a high risk of neurodevelopmental disability. The major type of injury involves cerebral white matter and the principal cellular target is the developing oligodendrocyte. The specific phase of the oligodendroglial lineage affected has been defined from study of both human brain and experimental models. This premyelinating cell (pre-OL) is vulnerable because of a series of maturation-dependent events. The pathogenesis of pre-OL injury relates to operation of two upstream mechanisms, hypoxia-ischemia and systemic infection/inflammation, both of which are common occurrences in premature infants. The focus of this review and of our research over the past 15-20 years has been the cellular and molecular bases for the maturation-dependent vulnerability of the pre-OL to the action of the two upstream mechanisms. Three downstream mechanisms have been identified, i.e., microglial activation, excitotoxicity and free radical attack. The work in both experimental models and human brain has identified a remarkable confluence of maturation-dependent factors that render the pre-OL so exquisitely vulnerable to these downstream mechanisms. Most importantly, elucidation of these factors has led to delineation of a series of potential therapeutic interventions, which in experimental models show marked protective properties. The critical next step, i.e., clinical trials in the living infant, is now on the horizon.

Prereading skills of very-low-birth-weight prematurely born Finnish children

Our objective was to study the prereading skills of very-low-birth-weight (VLBW; ≤ 1500 g) prematurely born children at the age of five years. A regional cohort of 89 VLBW children and 152 full-term (FT) born children was assessed for letter knowledge, phonological processing, and speeded naming. Full-scale IQ (FSIQ) was assessed using a short version of WPPSI-R. The associations of parental and neonatal factors, and FSIQ with prereading skills were assessed. VLBW group had poorer prereading skills, and there were more VLBW children at-risk (performing < -1 SD) compared to FT children in phonological processing (23% vs. 9%, p = .002), letter knowledge (27% vs. 14%, p = .017), and the accuracy of speeded naming (26% vs. 13%, p = .020). VLBW children had lower average FSIQ and Performance IQ (both comparisons p < .001) than FT controls, but Verbal IQ did not differ. When FSIQ was used as a covariate, VLBW children did not differ from the FT group in prereading skills indicating that they are at risk for more global developmental problems. Lower parental level of education as well as parent's reading problems were negatively associated with VLBW children's prereading skills. Positively, about 75% of VLBW children performed within the normal range in each individual prereading skill.

The developing oligodendrocyte: key cellular target in brain injury in the premature infant

Brain injury in the premature infant, a problem of enormous importance, is associated with a high risk of neurodevelopmental disability. The major type of injury involves cerebral white matter and the principal cellular target is the developing oligodendrocyte. The specific phase of the oligodendroglial lineage affected has been defined from study of both human brain and experimental models. This premyelinating cell (pre-OL) is vulnerable because of a series of maturation-dependent events. The pathogenesis of pre-OL injury relates to operation of two upstream mechanisms, hypoxia-ischemia and systemic infection/inflammation, both of which are common occurrences in premature infants. The focus of this review and of our research over the past 15-20 years has been the cellular and molecular bases for the maturation-dependent vulnerability of the pre-OL to the action of the two upstream mechanisms. Three downstream mechanisms have been identified, i.e., microglial activation, excitotoxicity and free radical attack. The work in both experimental models and human brain has identified a remarkable confluence of maturation-dependent factors that render the pre-OL so exquisitely vulnerable to these downstream mechanisms. Most importantly, elucidation of these factors has led to delineation of a series of potential therapeutic interventions, which in experimental models show marked protective properties. The critical next step, i.e., clinical trials in the living infant, is now on the horizon.

Incidence of necrotizing enterocolitis in very-low-birth-weight infants related to the use of Lactobacillus GG

BACKGROUND

One of the five level III neonatal intensive care units (NICU) in Finland has used prophylactic Lactobacillus GG (LGG) for very-low-birth-weight (VLBW) infants since 1997.

AIM

To examine retrospectively the incidence of necrotizing enterocolitis (NEC) in all five university hospital NICUs in Finland in relation to the use of LGG during the years each unit has belonged to the Vermont Oxford Network (VON).

METHODS

The incidence of NEC was analysed from the national database and from the VON databases separately in all five level III NICUs and additionally in three groups according to the probiotic practice in the hospitals: prophylactic LGG group, probiotics 'on demand' group and no probiotics group.

RESULTS

The incidence of NEC was 4.6% vs. 3.3% vs. 1.8% in the prophylactic LGG group, the no probiotics group and the probiotics 'on demand' group [corrected] respectively; p = 0.0090, chi-square. LGG had no influence on the clinical course of NEC.

CONCLUSIONS

The results of this retrospective report failed to show that LGG prophylaxis protects VLBW infants from the occurrence of NEC, in contrast to previously published results. Our results call for more research regarding effective ways to administer probiotics, including data on appropriate bacteria, strain, dose and timing of administration to achieve clinically robust effects.

Abnormal antenatal Doppler velocimetry and cognitive outcome in very-low-birth-weight infants at 2 years of age

OBJECTIVE

To study neurodevelopmental outcome at 2 years of corrected age in very-low-birth-weight (VLBW) (< or = 1500 g) preterm infants with abnormal fetoplacental flow.

METHODS

A total of 258 VLBW infants were born at Turku University Hospital between 2001 and 2006. Of these, 99 had undergone, within 1 week of delivery, antenatal Doppler assessment of blood flow in the umbilical artery (UA), fetal middle cerebral artery (MCA), descending aorta (DAo), aortic isthmus and ductus venosus and were eligible for inclusion in the study. Postnatally brain pathology was assessed by serial ultrasound and magnetic resonance imaging in 86 of the neonates and brain volume was measured in 80. Cognitive development was evaluated at 2 years of corrected age in 83 infants using the Bayley Scales of Infant Development-II. Motor development was assessed using the Hammersmith Infant Neurological Examination.

RESULTS

On univariate analysis, abnormal pulsatility index (PI) in the UA and an abnormal UA-PI/MCA-PI ratio (P = 0.04 and P = 0.003, respectively) as well as increases in both the DAo-PI and in the DAo-PI/MCA-PI ratio (P = 0.03 and P = 0.02, respectively), were associated with adverse cognitive outcome at 2 years of age. However, when controlling for cerebral volume using multivariate analysis, the association between abnormal antenatal Doppler characteristics and cognitive outcome became statistically non-significant, which indicated the determinant role of the volume reduction. Motor development was not associated with antenatal Doppler indices.

CONCLUSION

Abnormal antenatal Doppler indices are associated with adverse cognitive outcome at 2 years in VLBW infants. Our findings suggest that this association may be mediated through brain volume.