Birthweight and cognitive development during childhood

Associations between maternal folate status and choline intake during pregnancy and neurodevelopment at 3-4 years of age in the Alberta Pregnancy Outcomes and Nutrition (APrON) study

Folate and choline are methyl donor nutrients that may play a role in fetal brain development. Animal studies have reported that prenatal folate and choline supplementation are associated with better cognitive outcomes in offspring and that these nutrients may interact and affect brain development. Human studies that have investigated associations between maternal prenatal folate or choline levels and neurodevelopmental outcomes have reported contradictory findings and no human studies have examined the potential interactive effect of folate and choline on children's neurodevelopment. During the second trimester of pregnancy, maternal red blood cell folate was measured from blood samples and choline intake was estimated using a 24-h dietary recall in 309 women in the APrON cohort. At 3-5 years of age, their children's neurodevelopment was assessed using the Wechsler Preschool and Primary Scales of Intelligence - Fourth EditionCND, NEPSY-II language and memory subtests, four behavioral executive function tasks, and the Movement Assessment Battery for Children - Second Edition. Adjusted regressions revealed no associations between maternal folate and choline levels during pregnancy and most of the child outcomes. On the Dimensional Change Card Sort, an executive function task, there was an interaction effect; at high levels of choline intake (i.e., 1 SD above the mean; 223.03 mg/day), higher maternal folate status was associated with decreased odds of receiving a passing score (β = -0.44; 95%CI -0.81, -0.06). In conclusion, maternal folate status and choline intake during the second trimester of pregnancy were not associated with children's intelligence, language, memory, or motor outcomes at 3-4 years of age; however, their interaction may have an influence children's executive functions.

Is earlier obesity associated with poorer executive functioning later in childhood? Findings from the Millennium Cohort Study

BACKGROUND

Children affected with overweight or obesity have been associated with having lower educational achievement compared to peers who are non-overweight/obese. One of the drivers of this association could be a link between obesity and poorer executive function. Evidence is limited to small, cross-sectional studies which lack adjustment for important common causes.

OBJECTIVE

We investigate the association between weight status and executive function longitudinally in mid-childhood, accounting for potential common causes.

METHODS

Linear regression analyses were conducted to examine associations between weight status between 5 and 7 years and executive functioning at 11 years in members of the Millennium Cohort Study (n = 7739), accounting for a wide range of potential common causes. Age- and sex-specific International Obesity Taskforce cut-points for body mass index (BMI) were used. Executive function, including decision-making, impulsivity and spatial working memory, was assessed using the Cambridge Neuropsychological Test Automated Battery.

RESULTS

There were no unadjusted associations between weight status and decision-making or impulsivity. After adjustment for all potential common causes, there was a lack of consistent evidence to support an association between persistent obesity (including overweight) between 5 and 7 years and spatial working memory task at 11 years.

CONCLUSIONS

We found little evidence that poorer spatial working memory contributes to the association of children with obesity having lower educational achievement.

Mendelian randomization suggests that head circumference, but not birth weight and length, associates with intelligence

INTRODUCTION

Birth parameters have long been reported to have a role in human intelligence. However, the causalities reported in previous observational studies were controversial. Our study aims to provide an unbiased investigation of the causal associations between birth parameters and human intelligence using the Mendelian randomization (MR) approach.

METHODS

Genetic instrumental variables for MR analyses were extracted from large genome-wide association studies of infant head circumference (N = 10,768), birth length (N = 28,489), and birth weight (N = 321,223). Data for intelligence were obtained from a meta-analysis of genome-wide association studies of 269,867 individuals of the European ancestry. Primary MR analysis was performed using the standard inverse-variance weighted method, and sensitivity analyses were performed using the weighted median, MR-Egger, and MR-PRESSO methods.

RESULTS

Using 10 single nucleotide polymorphisms as instrumental variables, we found that 1 standard deviation increase in infant head circumference was associated with 0.14-fold higher scores in intelligence tests (β = 0.14, 95% confidence interval: 0.09 to 0.18, P_IVW =2.05 × 10^-9 ). The causal relationship was robust when sensitivity analyses were performed. However, birth length and birth weight had no significant associations with intelligence.

CONCLUSION

Our findings suggested infant head circumference, but not birth weight and length were associated with intelligence, which might indicate that brain development rather than general fetal growth was responsible for the development of intelligence.

Comparing Growth and Development of Low and Normal Birth Weight Children at Age of 60 Months

Background: Low birth weight (LBW < 2500 g) is one of the most serious problems in today’s world. It is also a predictor for mortality and stunting. Objectives: This study aimed to compare the growth and development at the age of 60 months between children born with low and normal birth weight in Shiraz, Iran. Methods: This study is part of the Fars birth cohort (FBC) study with the data of children who were born in 2011. We called mothers and asked them to bring their children to the FBC clinic for further evaluation. We also determined the level of development at the age of 60 months for each child by using the Ages and Stages questionnaire (ASQ) for the children. Results: Of the children, 304 (51.4%) were girls. Most of them had normal birth weight (93.2%), had exclusive breastfeeding for five to six months (79.9%), and did not have any chronic diseases (77.8%). Growth indices at the age of 60 months were significantly higher in children with normal birth weight than in their LBW peers (P < 0.001). However, we found no significant difference in children’s development at the age of 60 months between normal and low birth weight children. Conclusions: Although growth indices of children at the age of 60 months were higher in children with normal birth weight, we found no significant difference in children’s development at the age of 60 months between normal and low birth weight children.

Associations of birth size, infancy, and childhood growth with intelligence quotient at 5 years of age: a Danish cohort study

BACKGROUND

The correlates of prenatal and postnatal growth on Intelligence Quotient (IQ) in childhood in term-born children living in high-income countries are not well known.

OBJECTIVES

We examined how birth size and growth in infancy and childhood were associated with IQ at age 5 y in term-born children using path analysis.

METHODS

The study sample comprised 1719 children from the Danish National Birth Cohort who participated in a substudy in which psychologists assessed IQ using the Wechsler Primary and Preschool Scales of Intelligence-Revised. Measured weight, length/height, and head circumference at birth, 5 mo, 12 mo, and 5 y were included in a path model to estimate their total, indirect, and direct effects on IQ. All growth measures were included in the model as sex- and age-standardized z-scores.

RESULTS

After adjusting for potential confounders, a positive association between birth weight and IQ was observed, and 88% of the association was direct. Weight gain in infancy was associated with IQ [per z-score increase from 5 to 12 mo, IQ increased by 1.53 (95% CI: 0.14; 2.92) points] whereas weight gain from 12 mo to 5 y was not associated with IQ. Height and head circumference growth in childhood was associated with IQ [per z-score increase from 12 mo to 5 y, IQ increased by 0.98 (95% CI: 0.17; 1.79) and 2.09 (95% CI: 0.78; 3.41) points, respectively].

CONCLUSIONS

In children born at term in an affluent country with free access to health care, higher IQ was seen with greater size at birth and greater weight gain in infancy. Also, greater growth in height and head circumference throughout the first 5 y of life was associated with higher childhood IQ whereas greater weight gain after the first year of life was not.

Impact of maternal HIV infection on pregnancy outcomes in southwestern China - a hospital registry based study

Globally, human immune deficiency virus (HIV)/acquired immune deficiency syndrome (AIDS) continues to be a major public health issue. With improved survival, the number of people living with HIV/AIDS is increasing, with over 2 million among pregnant women. Investigating adverse pregnant outcomes of HIV-infected population and associated factors are of great importance to maternal and infant health. A cross-sectional data collected from hospital delivery records of 4397 mother-infant pairs in southwestern China were analysed. Adverse pregnant outcomes (including low birthweight/preterm delivery/low Apgar score) and maternal HIV status and other characteristics were measured. Two hundred thirteen (4.9%) mothers were HIV positive; maternal HIV infection, rural residence and pregnancy history were associated with all three indicators of adverse pregnancy outcomes. This research suggested that maternal population have high prevalence in HIV infection in this region. HIV-infected women had higher risks of experiencing adverse pregnancy outcomes. Rural residence predisposes adverse pregnancy outcomes. Findings of this study suggest social and medical support for maternal-infant care needed in this region, selectively towards rural areas and HIV-positive mothers.

Size at birth and cognitive function among rural adolescents: a life course epidemiology study protocol of the Kisalaya cohort in Mysuru, South India

INTRODUCTION

It is proven that adverse intrauterine environment results in 'early life programming,' alterations in metabolism and physiological development of the fetus, often termed as 'Developmental Origins of Health and Disease' (DOHaD) resulting in a smaller size at birth, greater non-communicable diseases (NCD) risk factors during childhood and adolescence, and cardiometabolic disorders in adulthood. Nevertheless, very few studies have examined the relationship between DOHaD programming and cognition. This study aims to examine if impaired prenatal growth indicated by birth weight is associated with cognition among adolescents in the Kisalaya cohort, a rural birth cohort in South India, thus providing newer insights into DOHaD programming for adolescent mental health in a low-income and middle-income country setting.

METHODS AND ANALYSIS

Kisalaya cohort was established in 2008, to provide integrated antenatal care and HIV testing using mobile clinics to improve maternal and child health outcomes. This cohort included pregnant women residing in 144 villages of Mysuru Taluk (rural) who received antenatal care through mobile clinics and delivered their children between 2008 and 2011. Data related to mother-infant dyads for all pregnant women who received care in the Kisalaya programme are available for this study. Presently, children born to women who received care through Kisalaya are adolescents between 10 and 12 years. At this point, information would be collected on sociodemographic data and assessments of mental health, stressful life events, cognition, vision, speech, language, hearing and anthropometric measures would be done and relevant maternal data and child data, available from the cohort would be retracted for analysis. We plan to retrace as many adolescents as possible out of 1544 adolescents who are currently available for study excluding twins, abortions, stillbirths and postdelivery deaths. Analyses will be extended to construct a life course pathway for cognition using structural equation modelling.

Determinants of Cognitive Development in the Early Life of Children in Bhaktapur, Nepal

Background

Children in low and middle income countries may have many risk factors for poor cognitive development, and are accordingly at a high risk of not reaching their developmental potential. Determinants for cognitive development in early life can be found among biological and socioeconomic factors, as well as in stimulation and learning opportunities.

Objective

The present study aimed to identify determinants of cognitive, language and motor development in 6–11 months old Nepalese infants.

Methods

Six hundred infants with a length-for-age z-score <-1 were assessed with the Bayley Scales of Infant and Toddler development, 3rd edition (Bayley-III). Information on socioeconomic factors, child and maternal demographics, clinical and biological factors, and the home environment were collected. In a manual stepwise variable selection procedure, we examined the association between selected biological, socioeconomic and stimulation and learning opportunity variables and the Bayley-III cognitive, language and motor development subscale scores in multiple linear regression models.

Results

The length-for-age z-scores was positively associated with the cognitive composite score [standardized beta (ß): 0.22, p < 0.001] and the motor composite score [(ß): 0.14, p = 0.001]. Children born with low birth weight (<2500 g) scored significantly lower on all subscale scores. Diarrheal history was associated with poor language composite scores, and females had higher language composite scores than boys [(ß): 0.11, p = 0.015]. Children who had been hospitalized during the first month of life had also lower cognitive and motor composite scores than those who had not been hospitalized. Parental reports of physical punishment and lack of spontaneous vocalization were associated with poor cognitive and language composite scores, respectively. The statistical models with the various subscale scores as dependent variables explained between 8 to 16 percent of the variability in the cognitive developmental outcomes.

Conclusion

Our findings reveal important determinants for developmental scores in infancy, and underline the role of biological risk factors faced by marginalized children in low and middle income countries such as in Nepal.

Acculturation or unequal assimilation? Smoking during pregnancy and duration of residence among migrants in Sweden

A growing corpus of evidence reveals that smoking patterns of migrant women tend to converge with that of the host population over time ('acculturation paradox'). In this paper we aim to adopt a health equity perspective by studying the extent to which this pattern reflects a convergence with the group of natives who are more socioeconomically disadvantaged. Using population-based registers, we study 1,194,296 women who gave birth in Sweden between 1991 and 2012. Using logistic regression, we estimated odds ratios to assess the effect of duration of residence on the association between smoking during pregnancy and women's origin (classified according to inequality-adjusted Human Development Index (iHDI) of the country of birth). Sibling information and multilevel models were used to assess the extent to which our results might be affected by the cross-sectional nature of the data. Smoking during pregnancy increases with duration of residence among migrants from all levels of iHDI to such an extent that they tend to converge or increase in relation to the levels of the Swedish population with low education and low income, leaving behind the native population with high education and income. The results are robust to possible selection bias related to the cross-sectional nature of the data. Our findings indicate the need of a health equity perspective and suggest the use of 'unequal assimilation' rather than 'acculturation paradox' as a more suitable framework to interpret these findings.

Acceptability and Reliability of the Bayley Scales of Infant and Toddler Development-III Among Children in Bhaktapur, Nepal

Background: The Bayley Scales of Infant and Toddler Development, 3rd edition (Bayley-III) is the most widely used developmental assessment tool for infants and toddlers worldwide, but less is known about its psychometric properties and feasibility in low and middle-income countries. Aim: To assess the psychometric properties and feasibility of the Bayley-III when used in a large scale randomized controlled intervention trial in Nepal. Methods: The participating infants were part of a randomized, doubled blind, placebo-controlled trial to measure the efficacy of vitamin B12 supplementation on growth and neurodevelopment. A total of 600 children aged 6-11 months were enrolled and included for developmental assessment. The Bayley-III measures child development across five domains: cognition, receptive and expressive language, fine and gross motor skills. Some items were culturally adapted. To measure and ensure appropriate inter-observer agreement, standardization exercises were performed during the initial training, and double scoring of 7% of test sessions were conducted throughout the study by two examiners. Results: The inter-rater agreement was excellent for both the standardization exercises before the start of the study, and for the quality control throughout the study with intraclass correlation coefficient ranging from 0.95 to 0.99. The internal consistency measured by the Cronbach's alpha coefficient ranged between 0.57 and 0.87. The subtests raw scores as well as scaled scores were significantly correlated (p < 0.001). The means and SDs of the scaled scores compared with American norms were similar to the distribution in the American sample, with the exception of the receptive (Mean = 7.7, SD = 2.2) and expressive (Mean = 7.3, SD = 1.9) language subtests that were lower than the American norms. Conclusion: The inter-rater reliability between the scorers on the Bayley-III was excellent both during standardization and for the quality control. The distributions for the cognitive and motor subscales are comparable to the American norms, while caution is needed in the interpretation of the language scales. The results suggest that Bayley-III is a feasible tool for the assessment of neurodevelopmental status in nutritional studies in low resource settings such as Nepal. Cultural adaptations, training and standardization are prerequisites for a valid and reliable assessment using the Bayley-III.

Preterm Birth, Poverty, and Cognitive Development

BACKGROUND

Preterm birth and childhood poverty each adversely impact children's cognitive development and academic outcomes. In this study, we investigated whether the relationships between preterm and early term birth and children's cognitive scores at 3, 5, and 7 years old were modified by childhood poverty.

METHODS

This study was conducted by using data on singletons born at 24 to 40 weeks' gestation enrolled in the Millennium Cohort Study in the United Kingdom. Linear regression models were used to test independent and joint associations of gestational age (early or moderate preterm, late preterm, or early term compared with term) and childhood poverty (<60% of median UK income) with children's cognitive scores. Presence of additive interaction between gestational age and poverty was tested by using interaction terms.

RESULTS

Children born preterm (<37 weeks) or early term (37-38 weeks) tended to score more poorly on cognitive assessments than children born at term (39-40 weeks). The estimated deficits were ∼0.2 to 0.3 SD for early or moderate preterm, 0.1 SD for late preterm, and 0.05 SD for early term compared with term. Children living in poverty scored 0.3 to 0.4 SD worse than children not living in poverty on all assessments. For most assessments, the estimated effects of the 2 factors were approximately additive, with little or no evidence of interaction between gestational age and poverty.

CONCLUSIONS

Although children born preterm who lived in poverty had the poorest cognitive outcomes, living in poverty did not magnify the adverse effect of being preterm on cognitive development.

Birth Weight and Intelligence in Young Adulthood and Midlife

OBJECTIVES

We examined the associations between birth weight and intelligence at 3 different adult ages.

METHODS

The Copenhagen Perinatal Cohort is comprised of children born in Copenhagen from 1959 to 1961. Information on birth weight and ≥1 tests of intelligence was available for 4696 members of the cohort. Intelligence was assessed at a mean age of 19 years with the Børge Priens Prøve test, at age 28 years with the Wechsler Adult Intelligence Scale, and at age 50 years with the Intelligenz-Struktur-Test 2000 R.

RESULTS

Birth weight was significantly associated with intelligence at all 3 follow-up assessments, with intelligence scores increasing across 4 birth weight categories and declining for the highest birth weight category. The adjusted differences between those in the <2.5kg birth weight group and those in the 3.5 to 4.00kg group were >5 IQ points at all 3 follow-up assessments, corresponding to one-third of a SD. The association was stable from young adulthood into midlife,and not weaker at age 50 years. Adjustment for potential confounding factors, including infant socioeconomic status and gestational age, did not dilute the associations, and associations with intelligence were evident across the normal birth weight range and so were not accounted for by low birth weight only.

CONCLUSIONS

The association between birth weight and intelligence is stable from young adulthood into midlife. These long-term cognitive consequences may imply that even small shifts in the distribution of birth size, in normal-sized infants as well, may have a large impact at the population level.

Birth characteristics and all-cause mortality: a sibling analysis using the Uppsala birth cohort multigenerational study

This paper investigates the association between perinatal health and all-cause mortality for specific age intervals, assessing the contribution of maternal socioeconomic characteristics and the presence of maternal-level confounding. Our study is based on a cohort of 12,564 singletons born between 1915 and 1929 at the Uppsala University Hospital. We fitted Cox regression models to estimate age-varying hazard ratios of all-cause mortality for absolute and relative birth weight and for gestational age. We found that associations with mortality vary by age and according to the measure under scrutiny, with effects being concentrated in infancy, childhood or early adult life. For example, the effect of low birth weight was greatest in the first year of life and then continued up to 44 years of age (HR between 2.82 and 1.51). These associations were confirmed in within-family analyses, which provided no evidence of residual confounding by maternal characteristics. Our findings support the interpretation that policies oriented towards improving population health should invest in birth outcomes and hence in maternal health.

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.

Prenatal Hemoglobin Levels and Early Cognitive and Motor Functions of One-Year-Old Children

OBJECTIVE

To explore the relationship between prenatal hemoglobin (Hb) concentration and infant cognitive and motor functions.

METHODS

Our prospective cohort study included 1-year-old children born to women enrolled at their first antenatal care (ANC) visit in Allada, Benin, before 29 weeks of pregnancy, within a trial comparing the efficacy of sulfadoxine-pyrimethamine and mefloquine. Hb concentrations of pregnant women were determined from venous blood samples collected at first and second ANC visits of at least 1-month interval and at delivery. Women were prescribed oral iron, folic acid, and anthelminthics after the first ANC visit. A total of 636 children (76.8% of eligible children) were assessed by trained research nurses for cognitive and motor functions by using the Mullen Scales of Early Learning.

RESULTS

Prevalence of anemia (Hb < 110 g/L) decreased from 67.0% at first ANC visit (mean gestational age [SD], 22.1 [4.0] weeks) to 38.4% at delivery. Mean (SD) Hb concentrations increased from 103.7 (12.3) at first ANC visit to 112.4 (14.1) at delivery. We observed a significant negative quadratic relationship between infant gross motor (GM) function and Hb concentration at first and second ANC visits. Thus, infant GM scores increased sharply with increasing maternal Hb concentration until 90 g/L where increasing GM was mild, and began to decline after 110 g/L.

CONCLUSIONS

There appears to be an Hb concentration range that may be optimal for GM function of 1-year-old children. This may reflect the importance of physiologic hemodilution, which occurs after the second trimester until 34 weeks of gestation.

Impact of helminth infection during pregnancy on cognitive and motor functions of one-year-old children

OBJECTIVE

To determine the effect of helminth infection during pregnancy on the cognitive and motor functions of one-year-old children.

METHODS

Six hundred and thirty five singletons born to pregnant women enrolled before 29 weeks of gestation in a trial comparing two intermittent preventive treatments for malaria were assessed for cognitive and motor functions using the Mullen Scales of Early Learning, in the TOVI study, at twelve months of age in the district of Allada in Benin. Stool samples of pregnant women were collected at recruitment, second antenatal care (ANC) visit (at least one month after recruitment) and just before delivery, and were tested for helminths using the Kato-Katz technique. All pregnant women were administered a total of 600 mg of mebendazole (100 mg two times daily for 3 days) to be taken after the first ANC visit. The intake was not directly observed.

RESULTS

Prevalence of helminth infection was 11.5%, 7.5% and 3.0% at first ANC visit, second ANC visit and at delivery, respectively. Children of mothers who were infected with hookworms at the first ANC visit had 4.9 (95% CI: 1.3-8.6) lower mean gross motor scores compared to those whose mothers were not infected with hookworms at the first ANC visit, in the adjusted model. Helminth infection at least once during pregnancy was associated with infant cognitive and gross motor functions after adjusting for maternal education, gravidity, child sex, family possessions, and quality of the home stimulation.

CONCLUSION

Helminth infection during pregnancy is associated with poor cognitive and gross motor outcomes in infants. Measures to prevent helminth infection during pregnancy should be reinforced.

The association of high birth weight with intelligence in young adulthood: a cohort study of male siblings

We aimed to explore why, in population studies, the positive association between normal-range birth weight and intelligence becomes negative at the highest birth weights. The study population comprised 217,746 Norwegian male singletons born at term between 1967 and 1976. All had data on birth weight and intelligence quotient (IQ) score at the time of military conscription; 137,574 had data on sibling birth weights; and 62,906 had data on male sibling birth weights. We estimated associations between birth weight and IQ score by ordinary least squares regression for the total study population and by fixed-effects regression for comparisons of brothers. The crude mean IQ score was 1.2 points (95% confidence interval (CI): 0.3, 2.2) lower for those with birth weights of 5,000 g or more compared with the reference group (with birth weights of 4,000-4,499 g). This difference leveled off to 0.0 (95% CI: -0.8, 0.9) in multivariable ordinary least squares regression and reversed to 2.2 points (95% CI: 0.3, 4.2) higher in fixed-effects regression. Results differed mainly because, at a given birth weight, participants who had a sibling with macrosomia had a lower mean IQ score. Nevertheless, within families with 1 or more macrosomic siblings, as in other families, men with higher birth weights tended to have higher IQ scores. Thus, a family-level confounder introduces a cross-level bias that cannot be detected in individual-level studies. We suggest ways in which future studies might elucidate the nature of this confounder.

Neurobehavioral consequences of chronic intrauterine opioid exposure in infants and preschool children: a systematic review and meta-analysis

BACKGROUND

It is assumed within the accumulated literature that children born of pregnant opioid dependent mothers have impaired neurobehavioral function as a consequence of chronic intrauterine opioid use.

METHODS

Quantitative and systematic review of the literature on the consequences of chronic maternal opioid use during pregnancy on neurobehavioral function of children was conducted using the Meta-analysis of Observational Studies in Epidemiology (MOOSE) and the Preferred Reporting Items for Systematic Reviews and Meta-Analysis (PRISMA) guidelines. We searched Cinahl, EMBASE, PsychINFO and MEDLINE between the periods of January 1995 to January 2012.

RESULTS

There were only 5 studies out of the 200 identified that quantitatively reported on neurobehavioral function of children after maternal opioid use during pregnancy. All 5 were case control studies with the number of exposed subjects within the studies ranging from 33-143 and 45-85 for the controls. This meta-analysis showed no significant impairments, at a non-conservative significance level of p < 0.05, for cognitive, psychomotor or observed behavioural outcomes for chronic intra-uterine exposed infants and pre-school children compared to non-exposed infants and children. However, all domains suggested a trend to poor outcomes in infants/children of opioid using mothers. The magnitude of all possible effects was small according to Cohen's benchmark criteria.

CONCLUSIONS

Chronic intra-uterine opioid exposed infants and pre-school children experienced no significant impairment in neurobehavioral outcomes when compared to non-exposed peers, although in all domains there was a trend to poorer outcomes. The findings of this review are limited by the small number of studies analysed, the heterogenous populations and small numbers within the individual studies. Longitudinal studies are needed to determine if any neuropsychological impairments appear after the age of 5 years and to help investigate further the role of environmental risk factors on the effect of 'core' phenotypes.

Birth weight and neurocognition in schizophrenia spectrum disorders

Low birth weight is associated with both schizophrenia and neurocognitive impairment. Yet, to our knowledge, no previous study has examined the relationship between lower birth weight and neurocognitive deficits in schizophrenia spectrum disorders (SSD). In this preliminary study, we investigated the relationship using a broad neuropsychological battery in cases with SSD and matched control subjects. The sample consisted of all subjects in the Developmental Insult and Brain Anomaly in Schizophrenia study, a nested case-control investigation developed from a large birth cohort, which followed subjects longitudinally. Case ascertainment was based on computerized record linkages between the birth cohort members and the Kaiser Permanente Medical Care Plan, and all diagnoses were confirmed by consensus diagnosis following the Diagnostic Interview for Genetic Studies. Lower birth weight was associated with impairment in executive function, working memory, generalized intellectual function, and neuromotor function in cases with SSD but not in control subjects. No deficits were observed in verbal memory for either group. These results support the hypothesis that lower birth weight plays a role in neuropsychological disruptions in SSD and that the antecedents of lower birth weight may have a greater impact on these disruptions in SSD than in controls. These data may facilitate a better understanding of the etiopathogenesis of the cognitive underpinnings of SSD.

Revisiting the effect of maternal smoking during pregnancy on offspring birthweight: a quasi-experimental sibling analysis in Sweden

Maternal smoking during pregnancy (SDP) seems associated with reduced birthweight in the offspring. This observation, however, is based on conventional epidemiological analyses, and it might be confounded by unobserved maternal characteristics related to both smoking habits and offspring birth weight. Therefore, we apply a quasi-experimental sibling analysis to revisit previous findings. Using the Swedish Medical Birth Register, we identified 677,922 singletons born between 2002 and 2010 from native Swedish mothers. From this population, we isolated 62,941 siblings from 28,768 mothers with discrepant habits of SDP. We applied conventional and mother-specific multilevel linear regression models to investigate the association between maternal SDP and offspring birthweight. Depending on the mother was light or heavy smoker and the timing of exposition during pregnancy (i.e., first or third trimester), the effect of smoking on birthweight reduction was between 6 and 78 g less marked in the sibling analysis than in the conventional analysis. Sibling analysis showed that continuous smoking reduces birthweight by 162 grams for mothers who were light smokers (1 to 9 cigarettes per day) and 226 g on average for those who were heavy smokers throughout the pregnancy in comparison to non-smoker mothers. Quitting smoking during pregnancy partly counteracted the smoking-related birthweight reduction by 1 to 29 g, and a subsequent smoking relapse during pregnancy reduced birthweight by 77 to 83 g. The sibling analysis provides strong evidence that maternal SDP reduces offspring birthweight, though this reduction was not as great as that observed in the conventional analysis. Our findings support public health interventions aimed to prevent SDP and to persuade those who already smoke to quit and not relapse throughout the pregnancy. Besides, further analyses are needed in order to explain the mechanisms through which smoking reduces birthweight and to identify other maternal characteristics that are common causes of both birthweight reduction and maternal smoking.

Reaching experience increases face preference in 3-month-old infants

The developing infant learns about the physical and the social world by engaging with objects and with people. In the study reported here, we investigated the relationship between infants' interactions with the physical and the social world. Three-month-old infants were trained for 2 weeks and experienced either actively manipulating objects themselves or passively having objects touched to their hands. Following active or passive experiences, spontaneous orienting towards faces and objects was compared between the trained groups and untrained 3- and 5-month-olds. It is known that the onset of reaching behavior increases infants' interest in objects. However, we report that active, self-produced reaching experiences also increase infants' spontaneous orienting towards faces, while passive experiences do not affect orienting behavior. Regression analyses provide evidence for a link between manual engagement and the development of orienting towards faces. Implications of orienting towards faces for the development of triadic interactions, joint attention, and social cognition in general are discussed.

Birth weight standardized to gestational age and intelligence in young adulthood: a register-based birth cohort study of male siblings

The authors aimed to determine the relation between birth-weight variations within the normal range and intelligence in young adulthood. A historical birth cohort study was conducted. Data from the Medical Birth Register of Norway were linked with register data from the Norwegian National Conscript Service. The sample comprised 52,408 sibships of full brothers who were born singletons at 37-41 completed weeks' gestation during 1967-1984 in Norway and were intelligence-tested at the time of mandatory military conscription. Generalized estimating equations were used to fit population-averaged panel data models. The analyses showed that in men with birth weights within the 10th-90th percentile range, a within-family difference of 1 standard deviation in birth weight standardized to gestational age was associated with a within-family difference of 0.07 standard deviation (99% confidence interval: 0.03, 0.09) in intelligence score, after adjustment for a range of background factors. There was no significant between-family association after adjustment for background factors. In Norwegian males, normal variations in intrauterine growth are associated with differences in intelligence in young adulthood. This association is probably not due to confounding by familial and parental characteristics.

HFE gene variants modify the association between maternal lead burden and infant birthweight: a prospective birth cohort study in Mexico City, Mexico

BACKGROUND

Neonatal growth is a complex process involving genetic and environmental factors. Polymorphisms in the hemochromatosis (HFE) iron regulatory genes have been shown to modify transport and toxicity of lead which is known to affect birth weight.

METHODS

We investigated the role of HFE C282Y, HFE H63 D, and transferrin (TF) P570 S gene variants in modifying the association of lead and infant birthweight in a cohort of Mexican mother-infant pairs. Subjects were initially recruited between 1994-1995 from three maternity hospitals in Mexico City and 411 infants/565 mothers had archived blood available for genotyping. Multiple linear regression models, stratified by either maternal/infant HFE or TF genotype and then combined with interaction terms, were constructed examining the association of lead and birthweight after controlling for covariates.

RESULTS

3.1%, 16.8% and 17.5% of infants (N=390) and 1.9%, 14.5% and 18.9% of mothers (N=533) carried the HFE C282Y, HFE H63D, and TF P570 S variants, respectively. The presence of infant HFE H63 D variants predicted 110.3 g (95% CI -216.1, -4.6) decreases in birthweight while maternal HFE H63 D variants predicted reductions of 52.0 g (95% CI -147.3 to 43.2). Interaction models suggest that both maternal and infant HFE H63 D genotype may modify tibia lead's effect on infant birthweight in opposing ways. In our interaction models, maternal HFE H63 D variant carriers had a negative association between tibia lead and birthweight.

CONCLUSIONS

These results suggest that the HFE H63 D genotype modifies lead's effects on infant birthweight in a complex fashion that may reflect maternal-fetal interactions with respect to the metabolism and transport of metals.

Association of birthweight and head circumference at birth to cognitive performance in 9- to 10-year-old children in South India: prospective birth cohort study

To examine whether birthweight and head circumference at birth are associated with childhood cognitive ability in South India, cognitive function was assessed using three core tests from the Kaufman Assessment Battery for children and additional tests measuring long-term retrieval/storage, attention and concentration, and visuospatial and verbal abilities among 505 full-term born children (mean age 9.7 y). In multiple linear regression adjusted for age, sex, gestation, socioeconomic status, parent's education, maternal age, parity, body mass index, height, rural/urban residence, and time of testing, Atlantis score (learning ability/long-term storage and retrieval) rose by 0.1 SD per SD increase in newborn weight and head circumference, respectively (p < 0.05 for all), and Kohs' block design score (visuospatial ability) increased by 0.1 SD per SD increase in birthweight (p < 0.05). The associations were reduced after further adjustment for current head circumference. There were no associations of birthweight and/or head circumference with measures of short-term memory, fluid reasoning, verbal abilities, and attention and concentration. In conclusion, higher birthweight and larger head circumference at birth are associated with better childhood cognitive ability. The effect may be specific to learning, long-term storage and retrieval, and visuospatial abilities, but this requires confirmation by further research.

The influence of birth size on intelligence in healthy children

OBJECTIVE

Birth parameters have been hypothesized to have an influence on IQ. However, studies within the range of normal birth size have been sparse. With this study we examined the associations between birth length, birth weight, head circumference, and gestational age within the normal birth size range in relation to childhood IQ in Asian children.

METHODS

A cohort of 1979 of 2913 Asian children aged 7 to 9 years, recruited from 3 schools in Singapore, were followed yearly from 1999 onward. Birth parameters were recorded by health personnel. Childhood IQ was measured with the Raven's Standard Progressive Matrices at ages 8 to 12.

RESULTS

The mean IQ score across the sample (n = 1645) was 114.2. After controlling for multiple confounders for every 1-cm increment in birth length, 1 kg in birth weight, or 1 cm in head circumference, there was a corresponding increase in IQ of 0.49 points (P for trend < .001), 2.19 points (P for trend = .007) and .62 points (P for trend = .003), respectively. These associations persisted even after exclusion of premature children and children with extreme weights and head circumferences.

CONCLUSIONS

Longer birth length, higher birth weight, or larger head circumferences within the normal birth size range are associated with higher IQ scores in Asian children. Our results suggest that antenatal factors reflected in altered rates of growth but within the normative range of pregnancy experiences play a role in generating cognitive potential. This has implications for targeting early intervention and preventative programs.

Socioeconomic position, maternal IQ, home environment, and cognitive development

OBJECTIVE

To assess whether socioeconomic position, maternal intelligence (IQ), and the home environment are inter-related to cognitive development in childhood.

STUDY DESIGN

Prospective cohort study (n = 723) with cognitive tests at ages 2, 4, 7, and 11 to 13 years.

RESULTS

There were statistically significant positive associations of father's occupational prestige, Home Observation for Measurement of Environment (HOME) score, and maternal IQ with cognitive performance in childhood. After adjustment for confounding factors, there was an increase in cognitive development by 0.8 to 2.0, 2.9 to 4.8, and 4.2 to 9.0 points for a 10-unit increment in father's occupational prestige, maternal IQ, and HOME score, respectively.

CONCLUSIONS

These results demonstrate that socioeconomic position, maternal IQ, and the home environment are independently and positively predictive of children's cognitive development. These findings provide additional rationale for implementing social policies that reduce socioeconomic inequalities.