Gestational age at birth and risk of autism spectrum disorders in Alberta, Canada

A case-control study on pre-, peri-, and neonatal risk factors associated with autism spectrum disorder among Armenian children

We aimed to investigate the role of pre-, peri- and neonatal risk factors in the development of autism spectrum disorder (ASD) among Armenian children with the goal of detecting and addressing modifiable risk factors to reduce ASD incidence. For this purpose a retrospective case-control study using a random proportional sample of Armenian children with ASD to assess associations between various factors and ASD was conducted. The study was approved by the local ethical committee, and parental written consent was obtained. A total of 168 children with ASD and 329 controls were included in the analysis. Multivariable logistic regression analysis revealed that male gender, maternal weight gain, use of MgB6, self-reported stress during the pregnancy, pregnancy with complications, as well as use of labor-inducing drugs were associated with a significant increase in the odds of ASD, whereas Duphaston use during pregnancy, the longer interpregnancy interval and birth height were associated with decreased odds of ASD. These findings are pertinent as many identified factors may be preventable or modifiable, underscoring the importance of timely and appropriate public health strategies aimed at disease prevention in pregnant women to reduce ASD incidence.

Association between interpregnancy interval and risk of autism spectrum disorder: a systematic review and Bayesian network meta-analysis

Although the risk of autism spectrum disorder (ASD) has been reported to be associated with interpregnancy intervals (IPIs), their association remains debatable due to inconsistent findings in existing studies. Therefore, the present study aimed to explore their association. PubMed, Embase, Web of Science, and the Cochrane Library were systematically retrieved up to May 25, 2022. An updated search was performed on May 25, 2023, to encompass recent studies. The quality of the included studies was assessed using the Newcastle-Ottawa Scale (NOS). Our primary outcome measures were expressed as adjusted odds ratios (ORs). Given various control measures for IPI and diverse IPI thresholds in the included studies, a Bayesian network meta-analysis was performed. Eight studies were included, involving 24,865 children with ASD and 2,890,289 children without ASD. Compared to an IPI of 24 to 35 months, various IPIs were significantly associated with a higher risk of ASD (IPIs < 6 months: OR = 1.63, 95% CI 1.53-1.74, n = 5; IPIs of 6-11 months: OR = 1.50, 95% CI 1.42-1.59, n = 4; IPIs of 12-23 months: OR = 1.19, 95% CI 1.12-1.23, n = 10; IPIs of 36-59 months: OR = 0.96, 95% CI 0.94-0.99, n = 2; IPIs of 60-119 months: OR = 1.15, 95% CI 1.10-1.20, n = 4; IPIs > 120 months: OR = 1.57, 95% CI 1.43-1.72, n = 4). After adjusting confounding variables, our analysis delineated a U-shaped restricted cubic spline curve, underscoring that both substantially short (< 24 months) and excessively long IPIs (> 72 months) are significantly correlated with an increased risk of ASD.  Conclusion: Our analysis indicates that both shorter and longer IPIs might predispose children to a higher risk of ASD. Optimal childbearing health and neurodevelopmental outcomes appear to be associated with a moderate IPI, specifically between 36 and 60 months. What is Known: • An association between autism spectrum disorder (ASD) and interpregnancy intervals (IPIs) has been speculated in some reports. • This association remains debatable due to inconsistent findings in available studies. What is New: • Our study delineated a U-shaped restricted cubic spline curve, suggesting that both shorter and longer IPIs predispose children to a higher risk of ASD. • Optimal childbearing health and neurodevelopmental outcomes appear to be associated with a moderate IPI, specifically between 36 and 60 months.

Environmental Risk Factors in Autism Spectrum Disorder: A Narrative Review

Existing evidence indicates that environmental factors might contribute up to 50% of the variance in autism spectrum disorder (ASD) risk. This structured narrative review offers a comprehensive synthesis of current knowledge on environmental risk factors in ASD, including evaluation of conflicting evidence, exploration of underlying mechanisms, and suggestions for future research directions. Analysis of diverse epidemiological investigations indicates that certain environmental factors, including advanced parental age, preterm birth, delivery complications, and exposure to toxic metals, drugs, air pollutants, and endocrine-disrupting chemicals, are linked to an increased ASD risk through various mechanisms such as oxidative stress, inflammation, hypoxia, and its consequences, changes in neurotransmitters, disruption of signaling pathways and some others. On the other hand, pregnancy-related factors such as maternal diabetes, maternal obesity, and caesarian section show a weaker association with ASD risk. At the same time, other environmental factors, such as vaccination, maternal smoking, or alcohol consumption, are not linked to the risk of ASD. Regarding nutritional elements data are inconclusive. These findings highlight the significance of environmental factors in ASD etiology and emphasize that more focused research is needed to target the risk factors of ASD. Environmental interventions targeting modifiable risk factors might offer promising avenues for ASD prevention and treatment.

Risk of Developmental Disorders in Children Born at 32 to 38 Weeks' Gestation: A Meta-Analysis

CONTEXT

Very preterm birth (<32 weeks) is associated with increased risk of developmental disorders. Emerging evidence suggests children born 32 to 38 weeks might also be at risk.

OBJECTIVES

To determine the relative risk and prevalence of being diagnosed with, or screening positive for, developmental disorders in children born moderately preterm, late preterm, and early term compared with term (≥37 weeks) or full term (39-40/41 weeks).

DATA SOURCES

Medline, Embase, Psychinfo, Cumulative Index of Nursing, and Allied Health Literature.

STUDY SELECTION

Reported ≥1 developmental disorder, provided estimates for children born 32 to 38 weeks.

DATA EXTRACTION

A single reviewer extracted data; a 20% sample was second checked. Data were pooled using random-effects meta-analyses.

RESULTS

Seventy six studies were included. Compared with term born children, there was increased risk of most developmental disorders, particularly in the moderately preterm group, but also in late preterm and early term groups: the relative risk of cerebral palsy was, for 32 to 33 weeks: 14.1 (95% confidence intervals [CI]: 12.3-16.0), 34 to 36 weeks: 3.52 (95% CI: 3.16-3.92) and 37 to 38 weeks: 1.44 (95% CI: 1.32-1.58).

LIMITATIONS

Studies assessed children at different ages using varied criteria. The majority were from economically developed countries. All were published in English. Data were variably sparse; subgroup comparisons were sometimes based on single studies.

CONCLUSIONS

Children born moderately preterm are at increased risk of being diagnosed with or screening positive for developmental disorders compared with term born children. This association is also demonstrated in late preterm and early term groups but effect sizes are smaller.

Research on the relationship between population distribution pattern and urban industrial facility agglomeration in China

Investigating the impact of industrial facility agglomeration on population distribution provides valuable insights for advancing urban and regional development, as well as aiding in planning, forecasting, and achieving regional equilibrium. However, there remains a notable gap in understanding the influence and mechanisms of industrial facility agglomeration on population distribution, particularly when considering different industry types and diverse regions comprehensively. Additionally, conventional panel data used to assess industrial facility agglomeration are constrained by limitations in coverage and timeliness. In contrast, Point of Interest (POI) data offers a superior solution with its real-time, fine-grained, and innovative advantages. This study utilizes real-time and fine-grained POI data in conjunction with the LandScan population raster dataset to precisely assess industrial facility agglomeration in 352 administrative units at the prefecture level and above in China. The key findings of this research can be summarized as follows: (1) factors influencing urban population growth rates have evolved, with increased significance attributed to Government Agencies and Social Groups, alongside a consistent impact from Science, Education, and Cultural Services. (2) The correlation between industrial facility agglomerations and population growth rates displayed linear relationships in 2015 and 2021, with varying strengths and directional shifts. (3) Regional disparities in industrial facility agglomeration patterns underscore the necessity for customized strategies to optimize industrial structures, foster innovation-driven sectors, and promote sustainable population growth.

The association between post-term births and autism spectrum disorders: an updated systematic review and meta-analysis

BACKGROUND

This study aimed to conduct a meta-analysis to determine whether post-term birth has an increased risk of ASD.

MATERIALS AND METHODS

To retrieve eligible studies regarding the effect of post-term and ASD in children, major databases including PubMed, Scopus, and Web of Science were searched. A random effect model was used for meta-analysis. For assessing the quality of included studies, the GRADE checklist was used.

RESULTS

In total, 18 records were included with 1,412,667 sample populations from 12 countries. The pooled estimates of RR and OR showed a significant association between post-term birth and ASD among children, respectively (RR = 1.34, 95% CI 1.10 to 1.58) and (OR = 1.47, 95% CI 1.03 to 1.91). There was no heterogeneity among the studies that reported the risk of ASD among children based on RR (I2 = 6.6%, P = 0.301). There was high heterogeneity in the studies reported risk of ASD based on OR (I2 = 94.1%, P = 0.000).

CONCLUSION

Post-term births still occur relatively frequently (up to 5-10%) even in developed countries. Our results showed that post-term birth is an increased risk of ASD, although high heterogeneity was found among the studies reported based on adjusted and crude forms, however, after subgroup analysis by gender, this heterogeneity disappeared among males.

Infection of the murine placenta by Listeria monocytogenes induces sex-specific responses in the fetal brain

BACKGROUND

Epidemiological data indicate that prenatal infection is associated with an increased risk of several neurodevelopmental disorders in the progeny. These disorders display sex differences in presentation. The role of the placenta in the sex-specificity of infection-induced neurodevelopmental abnormalities is not well-defined. We used an imaging-based animal model of the bacterial pathogen Listeria monocytogenes to identify sex-specific effects of placental infection on neurodevelopment of the fetus.

METHODS

Pregnant CD1 mice were infected with a bioluminescent strain of Listeria on embryonic day 14.5 (E14.5). Excised fetuses were imaged on E18.5 to identify the infected placentas. The associated fetal brains were analyzed for gene expression and altered brain structure due to infection. The behavior of adult offspring affected by prenatal Listeria infection was analyzed.

RESULTS

Placental infection induced sex-specific alteration of gene expression patterns in the fetal brain and resulted in abnormal cortical development correlated with placental infection levels. Furthermore, male offspring exhibited abnormal social interaction, whereas females exhibited elevated anxiety.

CONCLUSION

Placental infection by Listeria induced sex-specific abnormalities in neurodevelopment of the fetus. Prenatal infection also affected the behavior of the offspring in a sex-specific manner.

IMPACT

Placental infection with Listeria monocytogenes induces sexually dichotomous gene expression patterns in the fetal brains of mice. Abnormal cortical lamination is correlated with placental infection levels. Placental infection results in autism-related behavior in male offspring and heightened anxiety levels in female offspring.

Impact of Preterm Birth on Neurodevelopmental Disorders in South Korea: A Nationwide Population-Based Study

Neurodevelopmental disorder (NDD) in preterm infants has become of great interest. We aimed to investigate the impact of preterm birth on the proportion of NDD using nationwide data provided by the Korean National Health Insurance Service. We included 4894 extremely preterm or extremely low-birth-weight (EP/ELBW; <28 weeks of gestation or birth weight < 1000 g) infants, 70,583 other preterm or low-birth-weight (OP/LBW; 28−36 weeks of gestation or birth weight < 2500 g) infants, and 264,057 full-term infants born between 2008 and 2015. We observed their neurodevelopment until 6 years of age or until the year 2019, whichever occurred first. Diagnoses of NDDs were based on the World Health Organization’s International Classification of Diseases 10th revision. An association between preterm birth and NDD was assessed using a multivariable logistic regression model. There was a stepwise increase in the risk of overall NDD with increasing degree of prematurity, from OP/LBW (adjusted odds ratio 4.46; 95% confidence interval 4.34−4.58), to EP/ELBW (16.15; 15.21−17.15). The EP/ELBW group was strongly associated with developmental delay (21.47; 20.05−22.99), cerebral palsy (88.11; 79.89−97.19), and autism spectrum disorder (11.64; 10.37−13.06). Preterm birth considerably increased the risk of NDD by the degree of prematurity.

Influence of Prenatal Drug Exposure, Maternal Inflammation, and Parental Aging on the Development of Autism Spectrum Disorder

Autism spectrum disorder (ASD) affects reciprocal social interaction and produces abnormal repetitive, restrictive behaviors and interests. The diverse causes of ASD are divided into genetic alterations and environmental risks. The prevalence of ASD has been rising for several decades, which might be related to environmental risks as it is difficult to consider that the prevalence of genetic disorders related to ASD would increase suddenly. The latter includes (1) exposure to medications, such as valproic acid (VPA) and selective serotonin reuptake inhibitors (SSRIs) (2), maternal complications during pregnancy, including infection and hypertensive disorders of pregnancy, and (3) high parental age. Epidemiological studies have indicated a pathogenetic role of prenatal exposure to VPA and maternal inflammation in the development of ASD. VPA is considered to exert its deleterious effects on the fetal brain through several distinct mechanisms, such as alterations of γ-aminobutyric acid signaling, the inhibition of histone deacetylase, the disruption of folic acid metabolism, and the activation of mammalian target of rapamycin. Maternal inflammation that is caused by different stimuli converges on a higher load of proinflammatory cytokines in the fetal brain. Rodent models of maternal exposure to SSRIs generate ASD-like behavior in offspring, but clinical correlations with these preclinical findings are inconclusive. Hypertensive disorders of pregnancy and advanced parental age increase the risk of ASD in humans, but the mechanisms have been poorly investigated in animal models. Evidence of the mechanisms by which environmental factors are related to ASD is discussed, which may contribute to the development of preventive and therapeutic interventions for ASD.

Pregnant Mothers' Medical Claims and Associated Risk of Their Children being Diagnosed with Autism Spectrum Disorder

A retrospective analysis of administrative claims containing a diverse mixture of ages, ethnicities, and geographical regions across the United States was conducted in order to identify medical events that occur during pregnancy and are associated with autism spectrum disorder (ASD). The dataset used in this study is comprised of 123,824 pregnancies of which 1265 resulted in the child being diagnosed with ASD during the first five years of life. Logistic regression analysis revealed significant relationships between several maternal medical claims, made during her pregnancy and segmented by trimester, and the child's diagnosis of ASD. Having a biological sibling with ASD, maternal use of antidepressant medication and psychiatry services as well as non-pregnancy related claims such hospital visits, surgical procedures, and radiology exposure were related to an increased risk of ASD regardless of trimester. Urinary tract infections during the first trimester and preterm delivery during the second trimester were also related to an increased risk of ASD. Preventative and obstetrical care were associated with a decreased risk for ASD. A better understanding of the medical factors that increase the risk of having a child with ASD can lead to strategies to decrease risk or identify those children who require increased surveillance for the development of ASD to promote early diagnosis and intervention.

The prevalence and profile of autism in individuals born preterm: a systematic review and meta-analysis

INTRODUCTION

Preterm birth (<37 weeks) adversely affects development in behavioural, cognitive and mental health domains. Heightened rates of autism are identified in preterm populations, indicating that prematurity may confer an increased likelihood of adverse neurodevelopmental outcomes. The present meta-analysis aims to synthesise existing literature and calculate pooled prevalence estimates for rates of autism characteristics in preterm populations.

METHODS

Search terms were generated from inspection of relevant high-impact papers and a recent meta-analysis. Five databases were searched from database creation until December 2020 with PRISMA guidelines followed throughout.

RESULTS

10,900 papers were retrieved, with 52 papers included in the final analyses, further classified by assessment method (screening tools N=30, diagnostic assessment N=29). Pooled prevalence estimates for autism in preterm samples was 20% when using screening tools and 6% when using diagnostic assessments. The odds of an autism diagnosis were 3.3 times higher in individuals born preterm than in the general population.

CONCLUSIONS

The pooled prevalence estimate of autism characteristics in individuals born preterm is considerably higher than in the general population. Findings highlight the clinical need to provide further monitoring and support for individuals born preterm.

Placental DNA methylation changes and the early prediction of autism in full-term newborns

Autism spectrum disorder (ASD) is associated with abnormal brain development during fetal life. Overall, increasing evidence indicates an important role of epigenetic dysfunction in ASD. The placenta is critical to and produces neurotransmitters that regulate fetal brain development. We hypothesized that placental DNA methylation changes are a feature of the fetal development of the autistic brain and importantly could help to elucidate the early pathogenesis and prediction of these disorders. Genome-wide methylation using placental tissue from the full-term autistic disorder subtype was performed using the Illumina 450K array. The study consisted of 14 cases and 10 control subjects. Significantly epigenetically altered CpG loci (FDR p-value <0.05) in autism were identified. Ingenuity Pathway Analysis (IPA) was further used to identify molecular pathways that were over-represented (epigenetically dysregulated) in autism. Six Artificial Intelligence (AI) algorithms including Deep Learning (DL) to determine the predictive accuracy of CpG markers for autism detection. We identified 9655 CpGs differentially methylated in autism. Among them, 2802 CpGs were inter- or non-genic and 6853 intragenic. The latter involved 4129 genes. AI analysis of differentially methylated loci appeared highly accurate for autism detection. DL yielded an AUC (95% CI) of 1.00 (1.00-1.00) for autism detection using intra- or intergenic markers by themselves or combined. The biological functional enrichment showed, four significant functions that were affected in autism: quantity of synapse, microtubule dynamics, neuritogenesis, and abnormal morphology of neurons. In this preliminary study, significant placental DNA methylation changes. AI had high accuracy for the prediction of subsequent autism development in newborns. Finally, biologically functional relevant gene pathways were identified that may play a significant role in early fetal neurodevelopmental influences on later cognition and social behavior.

Distributional Properties and Criterion Validity of a Shortened Version of the Social Responsiveness Scale: Results from the ECHO Program and Implications for Social Communication Research

Prior work proposed a shortened version of the Social Responsiveness Scale (SRS), a commonly used quantitative measure of social communication traits. We used data from 3031 participants (including 190 ASD cases) from the Environmental Influences on Child Health Outcomes (ECHO) Program to compare distributional properties and criterion validity of 16-item "short" to 65-item "full" SRS scores. Results demonstrated highly overlapping distributions of short and full scores. Both scores separated case from non-case individuals by approximately two standard deviations. ASD prediction was nearly identical for short and full scores (area under the curve values of 0.87, 0.86 respectively). Findings support comparability of shortened and full scores, suggesting opportunities to increase efficiency. Future work should confirm additional psychometric properties of short scores.

Motor delay - An early and more common "red flag" in girls rather than boys with autism spectrum disorder

BACKGROUND

Autism and intellectual disability may coincide and be preceded by global developmental delay or by motor delay.

HYPOTHESIS

Motor delay in the context of global developmental delay is an initial "red flag" for ASD, with added risk in girls.

OBJECTIVE

To assess early developmental milestones in girls with ASD as compared to diagnosed boys, considering prematurity risk.

METHOD

Developmental milestones in a cohort of 467 children with ASD - diagnosed at mean age of 3.4 years (SD = 2.2) - were analyzed according to gender and prematurity risk.

RESULTS

111 girls (24 %), 356 boys (76 %), presented with motor milestones acquisition grossly within the normal range. However, there was a shift towards acquisition of walking being at the later end of the norm range, with this shift being more prominent in girls. 60 % of girls and 47 % of boys with ASD had motor delay and 49 % of girls and 36 % of boys had global developmental delay. The extent of the delays was greater in the prematurity subgroup.

CONCLUSION

Global delay of early milestones occurred in half of children with ASD and in 60 % of girls with ASD. Delayed acquisition of independent walking is relatively more common in girls subsequently diagnosed with ASD.

Autism risk linked to prematurity is more accentuated in girls

INTRODUCTION

Prematurity has been identified as a risk factor for Autism Spectrum Disorder (ASD). The link between Autism Spectrum Disorder (ASD) and birth-week has not been strongly evidenced. We evaluated the correlation between the degree of prematurity and the incidence of autism in a cohort of 871 children born prematurely and followed from birth. The cohort was reduced to 416 premature infants born between 2011-2017 who were followed for 2-14 years, and analyzed according to birth week (degree of prematurity), and according to gender.

RESULTS

43 children (10.3%) received a definite diagnosis of ASD. There was a significant correlation between birth week and the risk of ASD, with 22.6% of children diagnosed with ASD when born at 25 weeks, versus 6% of ASD diagnoses at 31 weeks of prematurity. For children born after 32 weeks, the incidence decreased to 8-12.5%. A strong link was found between earlier birth week and increased autism risk; the risk remained elevated during near-term prematurity in boys. A correlation between early birth week and an elevated risk for ASD was seen in all children, but accentuated in females, gradually decreasing as birth week progresses; in males the risk for ASD remains elevated for any birth week.

CONCLUSION

A statistically significant increase in rates of autism was found with each additional week of prematurity. Females drove this direct risk related to degree of prematurity, while males had an elevated risk throughout prematurity weeks, even at near-term. We recommend including ASD screening in follow up of infants born prematurely, at all levels of prematurity.

Association of Prenatal Exposure to Air Pollution With Autism Spectrum Disorder

IMPORTANCE

The etiology of autism spectrum disorder (ASD) is poorly understood, but prior studies suggest associations with airborne pollutants.

OBJECTIVE

To evaluate the association between prenatal exposures to airborne pollutants and ASD in a large population-based cohort.

DESIGN, SETTING, AND PARTICIPANTS

This population-based cohort encompassed nearly all births in Metro Vancouver, British Columbia, Canada, from 2004 through 2009, with follow-up through 2014. Children were diagnosed with ASD using a standardized assessment with the Autism Diagnostic Interview-Revised and Autism Diagnostic Observation Schedule. Monthly mean exposures to particulate matter with a diameter less than 2.5 µm (PM2.5), nitric oxide (NO), and nitrogen dioxide (NO2) at the maternal residence during pregnancy were estimated with temporally adjusted, high-resolution land use regression models. The association between prenatal air pollution exposures and the odds of developing ASD was evaluated using logistic regression adjusted for child sex, birth month, birth year, maternal age, maternal birthplace, and neighborhood-level urbanicity and income band. Data analysis occurred from June 2016 to May 2018.

EXPOSURES

Mean monthly concentrations of ambient PM2.5, NO, and NO2 at the maternal residence during pregnancy, calculated retrospectively using temporally adjusted, high-resolution land use regression models.

MAIN OUTCOMES AND MEASURES

Autism spectrum disorder diagnoses based on standardized assessment of the Autism Diagnostic Interview-Revised and Autism Diagnostic Observation Schedule. The hypothesis being tested was formulated during data collection.

RESULTS

In a cohort of 132 256 births, 1307 children (1.0%) were diagnosed with ASD by the age of 5 years. The final sample size for the PM2.5-adjusted model was 129 439 children, and for NO and NO2, it was 129 436 children; of these, 1276 (1.0%) were diagnosed with ASD. Adjusted odds ratios for ASD per interquartile range (IQR) were not significant for exposure to PM2.5 during pregnancy (1.04 [95% CI, 0.98-1.10] per 1.5 μg/m3 increase [IQR] in PM2.5) or NO2 (1.06 [95% CI, 0.99-1.12] per 4.8 ppb [IQR] increase in NO2) but the odds ratio was significant for NO (1.07 [95% CI, 1.01-1.13] per 10.7 ppb [IQR] increase in NO). Odds ratios for male children were 1.04 (95% CI, 0.98-1.10) for PM2.5; 1.09 (95% CI, 1.02-1.15) for NO; and 1.07 (95% CI, 1.00-1.13) for NO2. For female children, they were for 1.03 (95% CI, 0.90-1.18) for PM2.5; 0.98 (95% CI, 0.83-1.13) for NO; and 1.00 (95% CI, 0.86-1.16) for NO2.

CONCLUSIONS AND RELEVANCE

In a population-based birth cohort, we detected an association between exposure to NO and ASD but no significant association with PM2.5 and NO2.

Caesarean section and risk of autism across gestational age: a multi-national cohort study of 5 million births

Background

The positive association between caesarean section (CS) and autism spectrum disorder (ASD) may be attributed to preterm delivery. However, due to lack of statistical power, no previous study thoroughly examined this association across gestational age. Moreover, most studies did not differentiate between emergency and planned CS.

Methods

Using population-based registries of four Nordic countries and Western Australia, our study population included 4 987 390 singletons surviving their first year of life, which included 671 646 CS deliveries and 31 073 ASD children. We used logistic regression to estimate odds ratios (OR) and their 95% confidence intervals (CI) for CS, adjusted for gestational age, site, maternal age and birth year. Stratified analyses were conducted by both gestational age subgroups and by week of gestation. We compared emergency versus planned CS to investigate their potential difference in the risk of ASD.

Results

Compared with vaginal delivery, the overall adjusted OR for ASD in CS delivery was 1.26 (95% CI 1.22-1.30). Stratified ORs were 1.25 (1.15-1.37), 1.16 (1.09-1.23), 1.34 (1.28-1.40) and 1.17 (1.04-1.30) for subgroups of gestational weeks 26-36, 37-38, 39-41 and 42-44, respectively. CS was significantly associated with risk of ASD for each week of gestation, from week 36 to 42, consistently across study sites (OR ranged 1.16-1.38). There was no statistically significant difference between emergency and planned CS in the risk of ASD.

Conclusion

Across the five countries, emergency or planned CS is consistently associated with a modest increased risk of ASD from gestational weeks 36 to 42 when compared with vaginal delivery.

The manual orienting response habituation to repeated tactile stimuli in preterm neonates: Discrimination of stimulus locations and interstimulus intervals

Preterm infants frequently develop atypical sensory profiles, the tactile modality being particularly affected. However, there is a lack of recent investigation of neonatal tactile perception in a passive context, especially in preterms who are particularly exposed to this tactile stimuli. Our aims were to provide evidence of orienting responses (behavioral modifications directing subject's attention towards stimuli) and habituation to passive tactile stimuli in preterm neonates, to explore their ability to perceive spatial and temporal aspects of the stimulus, and to evaluate the effect of clinical factors on these abilities. We included 61 preterm neonates, born between 32 and 34 weeks of gestational age. At 35 weeks of corrected gestational age, we measured orienting responses (forearm, hand, and fingers movements) during vibrotactile stimulation of their hand and forearm; during a habituation and dishabituation paradigm, the dishabituation being either a location change or a pause in the stimulation sequence. Preterm newborns displayed a manual orienting response to vibrotactile stimuli which significantly decreased when the stimulus was repeated, regardless of the stimulated location on the limb. Habituation was delayed in subjects born at a younger gestational age, smaller birth weight, and having experienced more painful care procedures. Preterm neonates perceived changes in stimulus location and interstimulus time interval. Our findings provide insights on several aspects of the perception of repeated tactile stimuli by preterm neonates, and the first evidence of the early development of temporal processing abilities in the tactile modality. Future work will investigate the links between this ability and neurodevelopmental disorders.

Gestational age at birth and risk of intellectual disability without a common genetic cause

Preterm birth is linked to intellectual disability and there is evidence to suggest post-term birth may also incur risk. However, these associations have not yet been investigated in the absence of common genetic causes of intellectual disability, where risk associated with late delivery may be preventable. We therefore aimed to examine risk of intellectual disability without a common genetic cause across the entire range of gestation, using a matched-sibling design to account for unmeasured confounding by shared familial factors. We conducted a population-based retrospective study using data from the Stockholm Youth Cohort (n = 499,621) and examined associations in a nested cohort of matched outcome-discordant siblings (n = 8034). Risk of intellectual disability was greatest among those born extremely early (adjusted OR_{24 weeks} = 14.54 [95% CI 11.46-18.44]), lessening with advancing gestational age toward term (aOR_{32 weeks} = 3.59 [3.22-4.01]; aOR_37weeks = 1.50 [1.38-1.63]); aOR_{38 weeks} = 1.26 [1.16-1.37]; aOR₃₉ weeks = 1.10 [1.04-1.17]) and increasing with advancing gestational age post-term (aOR_{42 weeks} = 1.16 [1.08-1.25]; aOR_{43 weeks} = 1.41 [1.21-1.64]; aOR_{44 weeks} = 1.71 [1.34-2.18]; aOR_{45 weeks} = 2.07 [1.47-2.92]). Associations persisted in a cohort of matched siblings suggesting they were robust against confounding by shared familial traits. Risk of intellectual disability was greatest among children showing evidence of fetal growth restriction, especially when birth occurred before or after term. Birth at non-optimal gestational duration may be linked causally with greater risk of intellectual disability. The mechanisms underlying these associations need to be elucidated as they are relevant to clinical practice concerning elective delivery around term and mitigation of risk in post-term children.

Month of birth and risk of autism spectrum disorder: a retrospective cohort of male children born in Israel

BACKGROUND

Increased incidence and prevalence of autism spectrum disorder (ASD) over the last two decades have prompted considerable efforts to investigate its aetiological factors. We examined an association between month of birth and ASD incidence.

METHODS

In a retrospective cohort of male children born from January 1999 to December 2008 in a large health organisation in Israel (Maccabi Healthcare Services), ASD was followed from birth through December 2015.

RESULTS

Of 108 548 boys, 975 cases of ASD were identified. The highest rates (10.3 and 10.2 per 1000 male live births) were recorded for children born in May and August, respectively, and the lowest rates for February (7.6 per 1000 male live births). Among lower socioeconomic status households, boys born in August were more likely (OR=1.71; 95% CI 1.06 to 2.74) of being diagnosed with ASD than children born in January. Significantly higher rates were not observed for other months.

CONCLUSIONS

In line with several previous studies, we found a modestly higher likelihood of autism occurrence among male children of lower socioeconomic levels born in August.

Prevalence of Autism Spectrum Disorders with and without Intellectual Disability by Gestational Age at Birth in the Stockholm Youth Cohort: a Register Linkage Study

BACKGROUND

Preterm birth has been linked to increased risk of autism spectrum disorders (ASD), but how this risk changes with gestational age at birth has not been well characterised, especially with regard to co-occurring intellectual disability (ID).

METHODS

Register-based cohort study of singleton births in 1984-2007 in Stockholm County, Sweden (N total: 480 728; n ASD: 10 025). We assessed overall and sex-specific, gestational week-specific prevalence estimates and risk ratios of ASD with and without ID.

RESULTS

Preterm and postterm births were associated with elevated risk of ASD, and the relationship between gestational age at birth and ASD with and without ID differed in males and females. Risk of ASD without ID was higher in preterm births among both sexes and decreased continuously with increasing length of gestation. Risk of ASD with ID was higher in both preterm and postterm births among both sexes, with postterm birth in females being more highly associated with ASD with ID than that in males.

CONCLUSIONS

The relationship between gestational age at birth and ASD differs by the presence/absence of co-occurring ID and fetal sex. Both preterm and postterm birth are associated with increased risk of ASD. Risk of ASD is not constant within conventionally defined gestational age at birth periods. Further research on mechanism underlying these associations is needed.

Epigenetics of Autism Spectrum Disorder

Autism spectrum disorder (ASD), one of the most common childhood neurodevelopmental disorders (NDDs), is diagnosed in 1 of every 68 children. ASD is incredibly heterogeneous both clinically and aetiologically. The etiopathogenesis of ASD is known to be complex, including genetic, environmental and epigenetic factors. Normal epigenetic marks modifiable by both genetics and environmental exposures can result in epigenetic alterations that disrupt the regulation of gene expression, negatively impacting biological pathways important for brain development. In this chapter we aim to summarize some of the important literature that supports a role for epigenetics in the underlying molecular mechanism of ASD. We provide evidence from work in genetics, from environmental exposures and finally from more recent studies aimed at directly determining ASD-specific epigenetic patterns, focusing mainly on DNA methylation (DNAm). Finally, we briefly discuss some of the implications of current research on potential epigenetic targets for therapeutics and novel avenues for future work.

Neonatal and regressive forms of autism: Diseases with similar symptoms but a different etiology

Autistic Spectrum Disorder (ASD) can be a debilitating, life-long neurocognitive disease. ASD is caused by genetic and epigenetic factors and largely unknown and poorly understood environmental triggers. Signs and symptoms of ASD often appear in the first year of life while the disease strikes other infants who had previously been developing normally at around 2years of age. Ozonoff and her colleagues recently suggested that there are three different pathways or trajectories for the development of ASD in infants 6-24months of age. I hypothesize that pathway 1 is caused by in utero insult/injury, pathway 2 by obstetric complications at birth, and pathway 3 by environmental triggers of ASD affecting infants 0-3years of age. Faster progress can be made in elucidating the underlying causes of neonatal and regressive forms of ASD if the diseases are investigated separately, instead of being part of the same disorder.

Gender Affects Long-Term Neurological Outcome of Neonates

OBJECTIVE

We evaluated the possible association between fetal gender and long-term pediatric neurological morbidity.

METHODS

We performed a population-based retrospective cohort analysis comparing the risk of long-term neurological morbidity (up to age 18 years) of children born during the years 1991 to 2013 according to their gender. Neurological morbidity evaluated included hospitalizations in childhood involving pervasive developmental disorder, obstructive sleep apnea, cerebral palsy, epilepsy, and infantile spasms and disorders of eating as recorded in the hospital files. Multiple pregnancies and fetal congenital malformations were excluded. Kaplan-Meier survival curves were constructed to compare the cumulative neurological morbidity over the study period. A Cox proportional hazards model was used to control for obstetrical confounders, including gestational age at birth, birth weight, and maternal factors.

RESULTS

During the study period, 240,953 newborns were included in the long-term analysis: 51.0% (n = 122,840) males and 49.0% (n = 118,113) females. Hospitalizations for neurological problems (up to age 18 years) were significantly more common in males compared with females (1.1% vs 0.8%, respectively, odds ratio 1.31, 95% confidence interval 1.2 to 1.4, P < 0.001). Specifically, pervasive developmental disorder and obstructive sleep apnea were found to be significantly more common in males, and cerebral palsy reached borderline significance (0.1% vs 0.04%, odds ratio 1.39, 95% confidence interval 0.9 to 1.9, P = 0.06). The Kaplan-Meier survival curves demonstrated males to have a significantly higher cumulative incidence of total neurological morbidity as well as of pervasive developmental disorder and obstructive sleep apnea (all log-rank test P values <0.001). In the Cox regression model, male gender exhibited an independent association with long-term neurological morbidity, while adjusting for birth weight, gestational age, and other confounding variables (adjusted hazard ratio 1.29, 95% confidence interval 1.2 to 1.4, P < 0.001).

CONCLUSION

Males are at an increased risk for pediatric neurological morbidity independent of gestational age at birth and birth weight.

Validation of administrative and clinical case definitions for gestational diabetes mellitus against laboratory results

AIM

To examine the validity of International Classification of Disease, version 10 (ICD-10) codes for gestational diabetes mellitus in administrative databases (outpatient and inpatient), and in a clinical perinatal database (Alberta Perinatal Health Program), using laboratory data as the 'gold standard'.

METHODS

Women aged 12-54 years with in-hospital, singleton deliveries between 1 October 2008 and 31 March 2010 in Alberta, Canada were included in the study. A gestational diabetes diagnosis was defined in the laboratory data as ≥2 abnormal values on a 75-g oral glucose tolerance test or a 50-g glucose screen ≥10.3 mmol/l.

RESULTS

Of 58 338 pregnancies, 2085 (3.6%) met gestational diabetes criteria based on laboratory data. The gestational diabetes rates in outpatient only, inpatient only, outpatient or inpatient combined, and Alberta Perinatal Health Program databases were 5.2% (3051), 4.8% (2791), 5.8% (3367) and 4.8% (2825), respectively. Although the outpatient or inpatient combined data achieved the highest sensitivity (92%) and specificity (97%), it was associated with a positive predictive value of only 57%. The majority of the false-positives (78%), however, had one abnormal value on oral glucose tolerance test, corresponding to a diagnosis of impaired glucose tolerance in pregnancy.

CONCLUSIONS

The ICD-10 codes for gestational diabetes in administrative databases, especially when outpatient and inpatient databases are combined, can be used to reliably estimate the burden of the disease at the population level. Because impaired glucose tolerance in pregnancy and gestational diabetes may be managed similarly in clinical practice, impaired glucose tolerance in pregnancy is often coded as gestational diabetes.

The Changing Epidemiology of Autism Spectrum Disorders

Autism spectrum disorder (ASD) is a complex neurodevelopmental condition with lifelong impacts. Genetic and environmental factors contribute to ASD etiology, which remains incompletely understood. Research on ASD epidemiology has made significant advances in the past decade. Current prevalence is estimated to be at least 1.5% in developed countries, with recent increases primarily among those without comorbid intellectual disability. Genetic studies have identified a number of rare de novo mutations and gained footing in the areas of polygenic risk, epigenetics, and gene-by-environment interaction. Epidemiologic investigations focused on nongenetic factors have established advanced parental age and preterm birth as ASD risk factors, indicated that prenatal exposure to air pollution and short interpregnancy interval are potential risk factors, and suggested the need for further exploration of certain prenatal nutrients, metabolic conditions, and exposure to endocrine-disrupting chemicals. We discuss future challenges and goals for ASD epidemiology as well as public health implications.

Extremely low gestational age and very low birthweight for gestational age are risk factors for autism spectrum disorder in a large cohort study of 10-year-old children born at 23-27 weeks' gestation

BACKGROUND

No prospective cohort study of high-risk children has used rigorous exposure assessment and optimal diagnostic procedures to examine the perinatal antecedents of autism spectrum disorder separately among those with and without cognitive impairment.

OBJECTIVE

We sought to identify perinatal factors associated with increased risk for autism spectrum disorder with and without intellectual disability (intelligence quotient <70) in children born extremely preterm.

STUDY DESIGN

This prospective multicenter (14 institutions in 5 states) birth cohort study included children born at 23-27 weeks' gestation in 2002 through 2004 who were evaluated for autism spectrum disorder and intellectual disability at age 10 years. Pregnancy information was obtained from medical records and by structured maternal interview. Cervical-vaginal "infection" refers to maternal report of bacterial infection (n = 4), bacterial vaginosis (n = 30), yeast infection (n = 62), mixed infection (n = 4), or other/unspecified infection (n = 43; eg, chlamydia, trichomonas, or herpes). We do not know the extent to which infection per se was confirmed by microbial colonization. We use the terms "fetal growth restriction" and "small for gestational age" interchangeably in light of the ongoing challenge to discern pathologically from constitutionally small newborns. Severe fetal growth restriction was defined as a birthweight Z-score for gestational age at delivery <-2 (ie, ≥2 SD below the median birthweight in a referent sample that excluded pregnancies delivered for preeclampsia or fetal indications). Participants were classified into 4 groups based on whether or not they met rigorous diagnostic criteria for autism spectrum disorder and intellectual disability (autism spectrum disorder+/intellectual disability-, autism spectrum disorder+/intellectual disability+, autism spectrum disorder-/intellectual disability+, and autism spectrum disorder-/intellectual disability-). Temporally ordered multinomial logistic regression models were used to examine the information conveyed by perinatal factors about increased risk for autism spectrum disorder and/or intellectual disability (autism spectrum disorder+/intellectual disability-, autism spectrum disorder+/intellectual disability+, and autism spectrum disorder-/intellectual disability+).

RESULTS

In all, 889 of 966 (92%) children recruited were assessed at age 10 years, of whom 857 (96%) were assessed for autism spectrum disorder; of these, 840 (98%) children were assessed for intellectual disability. Autism spectrum disorder+/intellectual disability- was diagnosed in 3.2% (27/840), autism spectrum disorder+/intellectual disability+ in 3.8% (32/840), and autism spectrum disorder-/intellectual disability+ in 8.5% (71/840). Maternal report of presumed cervical-vaginal infection during pregnancy was associated with increased risk of autism spectrum disorder+/intellectual disability+ (odds ratio, 2.7; 95% confidence interval, 1.2-6.4). The lowest gestational age category (23-24 weeks) was associated with increased risk of autism spectrum disorder+/intellectual disability+ (odds ratio, 2.9; 95% confidence interval, 1.3-6.6) and autism spectrum disorder+/intellectual disability- (odds ratio, 4.4; 95% confidence interval, 1.7-11). Severe fetal growth restriction was strongly associated with increased risk for autism spectrum disorder+/intellectual disability- (odds ratio, 9.9; 95% confidence interval, 3.3-30), whereas peripartum maternal fever was uniquely associated with increased risk of autism spectrum disorder-/intellectual disability+ (odds ratio, 2.9; 95% confidence interval, 1.2-6.7).

CONCLUSION

Our study confirms that low gestational age is associated with increased risk for autism spectrum disorder irrespective of intellectual ability, whereas severe fetal growth restriction is strongly associated with autism spectrum disorder without intellectual disability. Maternal report of cervical-vaginal infection is associated with increased risk of autism spectrum disorder with intellectual disability, and peripartum maternal fever is associated with increased risk for intellectual disability without autism spectrum disorder.

Validation of administrative data case definitions for gestational diabetes mellitus

AIM

To examine, using administrative data, the validity of two algorithms for identifying gestational diabetes mellitus: 1) the current National Diabetes Surveillance System algorithm for excluding gestational diabetes cases and 2) gestational diabetes-specific ICD codes in the delivery-related hospitalization.

METHODS

This was a retrospective study of all women, aged 18-54 years, residing in Alberta, Canada, with singleton deliveries between 1 April 1999 and 31 March 2010. We linked Alberta Perinatal Health Program data on all deliveries to administrative claims data from Alberta Health using the mother's personal health number. For both gestational diabetes algorithms, we calculated the sensitivity, specificity, positive predictive value, negative predictive value and agreement, using gestational diabetes identified in the Alberta Perinatal Health Program as the 'gold standard'.

RESULTS

Our study sample consisted of 411 390 deliveries for 273 152 women. The mean (sd) age was 29.1 (5.6) years and 82.3% of the women were white. Crude rates of gestational diabetes were 3.9% (16 215 cases), 1.3% (5189 cases) and 4.0% (16 440 cases) according to the Alberta Perinatal Health Program, National Diabetes Surveillance System and ICD code-based algorithms, respectively. Compared with the Alberta Perinatal Health Program database, the National Diabetes Surveillance System algorithm had a sensitivity of 25% and specificity of 100%, whereas the gestational diabetes-specific ICD code-based algorithm had a sensitivity of 86% and specificity of 99%.

CONCLUSIONS

The National Diabetes Surveillance System algorithm underestimates the number of gestational diabetes cases. A more valid mechanism to identify gestational diabetes prevalence using health administrative data is the use of gestational diabetes-specific ICD-9/10 codes in the delivery hospitalization.

Extremely Preterm Born Children at Very High Risk for Developing Autism Spectrum Disorder

This study aimed to provide a more comprehensive picture of the prevalence of autism spectrum disorder (ASD) in a geographic cohort of extremely preterm born adolescents by using established diagnostic instruments in addition to screening instruments. 53 participants passed a screening procedure with two screening instruments and a diagnostic evaluation with a semi-structured assessment and a parent interview. 28 % of the adolescents had a community based clinical diagnosis of ASD. When research diagnoses were also taken into account, this rate increased to 40 %. Intellectual disability, language impairment and behavioural difficulties are characteristic for these children with ASD. This study is to our knowledge the first to use ASD-specific diagnostic instruments to confirm ASD diagnoses in extremely preterm born children in early adolescence. The study expands findings of previous research and raises the need for follow-up into late childhood and early adolescence.

Stability of early risk assessment for autism spectrum disorder in preterm infants

Stability and change in early autism spectrum disorder risk were examined in a cohort of 99 preterm infants (⩽34 weeks of gestation) using the Autism Observation Scale for Infants at 8 and 12 months and the Autism Diagnostic Observation Schedule—Toddler Module at 18 months. A total of 21 infants were identified at risk by the Autism Observation Scale for Infants at 8 months, and 9 were identified at risk at 12 months, including 4 children who were not previously identified. At 18 months, eight children were identified at risk for autism spectrum disorder using the Autism Diagnostic Observation Schedule—Toddler Module, only half of whom had been identified using the original Autism Observation Scale for Infants cutoffs. Results are discussed in relation to early trajectories of autism spectrum disorder risk among preterm infants as well as identifying social-communication deficiencies associated with the early preterm behavioral phenotype.

Pregnancy risk factors in autism: a pilot study with artificial neural networks

BACKGROUND

Autism is a multifactorial condition in which a single risk factor can unlikely provide comprehensive explanation for the disease origin. Moreover, due to the complexity of risk factors interplay, traditional statistics is often unable to explain the core of the problem due to the strong inherent nonlinearity of relationships. The aim of this study was to assess the frequency of 27 potential risk factors related to pregnancy and peri-postnatal period.

METHODS

The mothers of 45 autistic children and of 68 typical developing children completed a careful interview. Twenty-four siblings of 19 autistic children formed an internal control group.

RESULTS

A higher prevalence of potential risk factors was observed in 22 and 15 factors in external control and internal control groups, respectively. For six of them, the difference in prevalence was statistically significant. Specialized artificial neural networks (ANNs) discriminated between autism and control subjects with 80.19% global accuracy when the dataset was preprocessed with TWIST (training with input selection and testing) system selecting 16 out of 27 variables. Logistic regression applied to 27 variables gave unsatisfactory results with global accuracy of 46%.

CONCLUSION

Pregnancy factors play an important role in autism development. ANNs are able to build up a predictive model, which could represent the basis for a diagnostic screening tool.

A Simulation Study of Categorizing Continuous Exposure Variables Measured with Error in Autism Research: Small Changes with Large Effects

Variation in the odds ratio (OR) resulting from selection of cutoffs for categorizing continuous variables is rarely discussed. We present results for the effect of varying cutoffs used to categorize a mismeasured exposure in a simulated population in the context of autism spectrum disorders research. Simulated cohorts were created with three distinct exposure-outcome curves and three measurement error variances for the exposure. ORs were calculated using logistic regression for 61 cutoffs (mean ± 3 standard deviations) used to dichotomize the observed exposure. ORs were calculated for five categories with a wide range for the cutoffs. For each scenario and cutoff, the OR, sensitivity, and specificity were calculated. The three exposure-outcome relationships had distinctly shaped OR (versus cutoff) curves, but increasing measurement error obscured the shape. At extreme cutoffs, there was non-monotonic oscillation in the ORs that cannot be attributed to “small numbers.” Exposure misclassification following categorization of the mismeasured exposure was differential, as predicted by theory. Sensitivity was higher among cases and specificity among controls. Cutoffs chosen for categorizing continuous variables can have profound effects on study results. When measurement error is not too great, the shape of the OR curve may provide insight into the true shape of the exposure-disease relationship.

A functional approach to cerebral visual impairments in very preterm/very-low-birth-weight children

BACKGROUND

Cerebral visual impairment (CVI) is a major cause of visual impairment, with very preterm birth/very low birth weight (VP/VLBW) being a major risk factor. There is no generally accepted definition of CVI. This study aims to investigate the usefulness of an empirically-based functional definition of CVI.

METHODS

One-hundred-five VP/VLBW children and 67 controls participated. CVI was defined after comprehensive oculomotor, visual sensory and perceptive assessment, and validated against vision problems in daily life and in terms of intellectual, behavioral, emotional and social functioning, as well as use of therapeutic services.

RESULTS

Twenty-four per cent of the VP/VLBW children met criteria for CVI, compared to 7% of controls (P = 0.006, OR: 3.86, 95% CI: 1.40-10.70). VP/VLBW children with CVI had lower performance IQ, but not verbal IQ, than those without CVI. Visual problems in daily life were confirmed in VP/VLBW children classified with CVI. Additionally, difficulties in behavioral and social functioning were most prominent among VP/VLBW children with CVI.

CONCLUSION

In VP/VLBW children, CVI defined in terms of visual function deficits is accompanied by intellectual, behavioral, and social impairments, validating our operational definition of CVI. CVI might act as a marker for developmental problems in VP/VLBW children.

Impact of gestational diabetes mellitus and high maternal weight on the development of diabetes, hypertension and cardiovascular disease: a population-level analysis

AIMS

To examine the association between gestational diabetes mellitus (GDM) and high maternal weight and the risk of development of chronic disease.

METHODS

Women with singleton deliveries between April 1999 and March 2010 in Alberta, Canada, were categorized according to pre-pregnancy weight (overweight ≥ 91 kg) and GDM status. Obstetric and neonatal outcomes, as well as the long-term incidence of maternal diabetes, hypertension and cardiovascular disease were examined.

RESULTS

Of 240 083 women, 213 765 (89%) had no GDM and were not overweight (reference group), 17 587 (7.3%) were overweight only, 7332 (3%) had GDM only and 1399 (0.6%) had GDM and were overweight. Significant differences in Caesarean section rates, induction rates and birthweight were observed across the four groups. During a median follow-up of 5.3 years, diabetes incidence was 36% in the GDM and overweight, 18.8% in the GDM only, 4.8% in the overweight only and 1.1% in the reference group. With respect to hypertension and cardiovascular disease, the GDM and overweight group had the highest rates (26.8% and 3.1%, respectively) and the reference group had the lowest rates (5.8% and 1.0%, respectively). However, rates were similar in the GDM only (14.9% and 1.9%, respectively) and overweight only groups (14.9% and 1.5%, respectively).

CONCLUSIONS

Not surprisingly, the presence of both high maternal weight and GDM compounds the risk of developing diabetes. However, the association between overweight alone and GDM alone and hypertension and cardiovascular disease appears similar suggesting a need for effective interventions to manage both these conditions to improve the health of these patients.

Maternal obesity and increased risk for autism and developmental delay among very preterm infants

OBJECTIVE

Thirty-five percent of women of child-bearing age are obese, and there is evidence that maternal obesity may increase the risk for adverse neurodevelopmental outcome. However, research regarding obesity and neurodevelopment among children born preterm is limited. This study aimed to determine associations between maternal obesity and neurodevelopment in very preterm children at age 2 years.

STUDY DESIGN

Maternal/infant dyads (n=62) born ⩽30 weeks gestation were enrolled in a prospective cohort study at a level-III neonatal intensive care unit. Mothers were classified as obese or non-obese based on pre-pregnancy body mass index. Infants underwent magnetic resonance imaging at term equivalent and developmental testing at age 2. Maternal obesity was investigated for associations with neurodevelopment.

RESULT

Maternal obesity was associated with positive screen for autism (odds ratio=9.88, P=0.002) and lower composite language scores (β=-9.36, (confidence interval=-15.11, -3.61), P=0.002).

CONCLUSION

Maternal obesity was associated with adverse neurodevelopmental outcome at age 2 in this cohort of very preterm children. This study requires replication, but may support targeted surveillance of infants born to women with maternal obesity.

Quantifying the potential impact of measurement error in an investigation of autism spectrum disorder (ASD)

The Early Autism Risk Longitudinal Investigation (EARLI), an ongoing study of a risk-enriched pregnancy cohort, examines genetic and environmental risk factors for autism spectrum disorders (ASDs). We simulated the potential effects of both measurement error (ME) in exposures and misclassification of ASD-related phenotype (assessed as Autism Observation Scale for Infants (AOSI) scores) on measures of association generated under this study design. We investigated the impact on the power to detect true associations with exposure and the false positive rate (FPR) for a non-causal correlate of exposure (X2, r=0.7) for continuous AOSI score (linear model) versus dichotomised AOSI (logistic regression) when the sample size (n), degree of ME in exposure, and strength of the expected (true) OR (eOR)) between exposure and AOSI varied. Exposure was a continuous variable in all linear models and dichotomised at one SD above the mean in logistic models. Simulations reveal complex patterns and suggest that: (1) There was attenuation of associations that increased with eOR and ME; (2) The FPR was considerable under many scenarios; and (3) The FPR has a complex dependence on the eOR, ME and model choice, but was greater for logistic models. The findings will stimulate work examining cost-effective strategies to reduce the impact of ME in realistic sample sizes and affirm the importance for EARLI of investment in biological samples that help precisely quantify a wide range of environmental exposures.

Prevalence and neonatal factors associated with autism spectrum disorders in preterm infants

OBJECTIVES

To determine the prevalence of autism spectrum disorders (ASD) across gestational age, examine the risk of ASD by gestational age controlling for other risk factors, and identify potential risk factors in the neonatal intensive care unit.

STUDY DESIGN

A retrospective cohort of infants born at ≥ 24 weeks between January 1, 2000, and December 31, 2007 at 11 Kaiser Permanente Northern California hospitals (n = 195,021). ASD cases were defined by a diagnosis made at a Kaiser Permanente ASD evaluation center, by a clinical specialist, or by a pediatrician. Cox proportional hazards regression models were used to evaluate the association between gestational age and ASD as well as potential risk factors in the neonatal intensive care unit and ASD.

RESULTS

The prevalence of ASD in infants <37 weeks was 1.78% compared with 1.22% in infants born ≥ 37 weeks (P < .001). Compared with term infants, infants born at 24-26 weeks had an adjusted hazard ratio (HR) for a diagnosis of ASD of 2.7 (95% CI 1.5-5.0). Infants born at 27-33 weeks (adjusted HR 1.4, 95% CI 1.1-1.8) and 34-36 weeks (adjusted HR 1.3, 95% CI 1.1-1.4) were also at increased risk. High frequency ventilation and intracranial hemorrhage were associated with ASD in infants < 34 weeks.

CONCLUSIONS

ASD was ~ 3 times more prevalent in infants <27 weeks compared with term infants. Each week of shorter gestation was associated with an increased risk of ASD. High frequency ventilation and intracranial hemorrhage were associated with ASD among infants <34 weeks.

Comparison of three screening tests for autism in preterm children with birth weights less than 1,500 grams

BACKGROUND

Preterm children seem to be at increased risk for autism spectrum disorders (ASD).

METHODS

Parents of 157 children with birth weights less than 1,500 g (age 2 years, corrected for prematurity; 88 boys, 69 girls) completed screening questionnaires. The screening battery included the Modified Checklist for Autism in Toddlers (M-CHAT), Communication and Symbolic Behavior Scales Developmental Profile Infant-Toddler Checklist (CSBS-DP-ITC), and the Infant/Toddler Sensory Profile (ITSP). Children with disabilities were excluded. All children who screened positive on any of the screening tools were subsequently assessed by clinical examination including the Autism Diagnostic Observation Schedule.

RESULTS

Fifty-six children (35.7%) screened positive on at least one of the parental screening questionnaires. Of the 56 children who tested positive, 33 participated in the detailed clinical follow-up assessment. A diagnosis of ASD was confirmed in 13 of the 33 children. The ASD prevalence was 9.7% of the sample. Analysis of children with and without an ASD diagnosis found significant differences relative to gestational age (26.9 weeks vs 28.3 weeks, P=0.033) and length of the stay in hospital (89.5 days vs 75.4 days, P=0.042). The screening tool with the most positive results was CSBS-DP-ITC (42 positive screens [PS]), followed by M-CHAT (28 PS), and ITSP (22 PS). Differences in the frequency of PS among the tests were significant (P=0.008). CSBS-DP-ITC had the highest sensitivity (0.846), followed by M-CHAT (0.692) and ITSP (0.462).

CONCLUSION

Our results indicate a higher prevalence of autism in children with birth weights <1,500 g at 2 years of age compared to the general population prevalence. The ASD diagnosis was associated with shorter gestation times and longer hospital stays. Our findings support the simultaneous use of more than one screening tests in order to increase screening sensitivity.