Cognitive development of term small for gestational age children at five years of age

Association of growth in utero with cognitive function at age 6-8 years

BACKGROUND

Size at birth is associated with later cognitive development. The timing of growth faltering in utero may affect developmental consequences.

AIM

To determine whether growth in utero is related to cognitive outcomes in childhood. A secondary aim was to determine any associations between maternal nutritional status and cognition.

STUDY DESIGN AND SUBJECTS

Subjects were participants in a prospective cohort study of developmental origins of adult disease. Eligible subjects were aged 6-8 years at their next scheduled visit to the study clinic and their mothers had abdominal ultrasound measurements at 14, 25 and 35 weeks gestation. 186 of 264 eligible children attended the clinic and were tested.

OUTCOME MEASURES

Raven's Progressive Matrices (reasoning ability), Peabody Picture Vocabulary Test (receptive vocabulary) and Digit Span Forwards (auditory working memory).

RESULTS

In multiple regression analyses controlling for children's age and socioeconomic status, head circumference at 14 weeks gestation was significantly associated with reasoning ability. The difference between the lowest and highest quartiles was equivalent to 0.4 S.D. No other significant associations with fetal growth were found. Maternal weight gain was not associated with cognitive scores; however, change in triceps skinfold between 25 and 35 weeks gestation was positively associated with reasoning ability and remained a significant predictor when included in the regression model.

CONCLUSIONS

There were few associations between growth in utero and cognition. Growth in head circumference in early gestation and maternal nutrition in late gestation may affect later cognitive ability. Further research in this area is needed to confirm these results.

Longitudinal follow-up of height up to five years of age in infants born preterm small for gestational age; comparison to full-term small for gestational age infants

OBJECTIVE

This aims to conduct a comparative study of the height catch-up rate in preterm small for gestational age (SGA) infants during early childhood by gestational age and identify the factors affecting short stature in comparison to full-term SGA infants.

METHODS

449 SGA infants (214 full-term infants, 73 infants with gestation of less than 32 weeks, and 162 infants with gestation of more than 32 weeks but less than 37 weeks) from 25 institutions in Japan were assessed for catch-up (> or = -2SD) rate in growth by measuring for length/height at 1 year, 3 years and 5 years of age and the risk factors for no catch-up (< -2SD) at 5 years.

RESULTS

The overall length/height catch-up rate was 68% at 1 year, 89% at 3 years and 88% at 5 years. The catch-up rate at 3 and 5 years of age in the group with gestation of less than 32 weeks had a rate of 74%, which was significantly less than the other two groups (approximately 90%). A significant factor associated with short stature at 5 years in the group with gestation of less than 32 weeks was the lower length SD score at time of birth, and for preterm infants born more than 32 weeks of gestation and full-term infants, significant factors were the lower maternal height and head circumference at birth.

CONCLUSION

SGA infants born less than 32 weeks of gestation had a higher risk of no catch-up and different factors affecting catch-up compared to preterm SGA infants of gestation more than 32 weeks and full-term SGA infants.

Intellectual development in a Danish cohort of prematurely born preschool children: specific or general difficulties?

A national cohort of extremely low birth weight (ELBW) and/or extremely preterm (EPT) children and a term control group was followed up at the age of 5 years. The primary objective was to investigate whether premature birth had a global impact on cognitive functions or affected specific functions only. Assessment tools were Wechsler Preschool and Primary Scale of Intelligence-Revised (WPPSI-R), Movement Assessment Battery for Children (M-ABC), and subtests from the Neuropsychological Assessment 4-7 years (NEPSY). The mean Full Scale IQ (FSIQ) and M-ABC score of the index children were 1.1 and 1.2 SDs lower than that of the control children (p <.001). Most WPPSI-R subtests showed medium to large differences between index and control children, suggesting a global impact of premature birth on cognitive functions. For both unadjusted and FSIQ adjusted means, no significant group differences on tests of memory or executive function were observed (p >.1), suggesting little impact of premature birth on these specific functions. In this sample, cognitive difficulties in 5-year-old ELBW and/or EPT children tended to be associated with general intellectual difficulties rather than with specific dysfunctions; however, the implications of this finding are ambiguous due to substantial attrition on the NEPSY subtests.

The Relative Effect of Size at Birth, Postnatal Growth and Social Factors on Cognitive Function in Late Childhood

PURPOSE

To investigate if fetal, head, and somatic postnatal growth are independent predictors of cognition and estimate their relative importance compared to the effect size of social factors on cognitive function at 10 years.

METHODS

Longitudinal population-based data from the birth questionnaire and the 5- and 10-year sweeps of the 1970 British Birth Cohort Study were used, including 11,244 subjects. Multiple linear regression and structural equation modeling were used in the statistical analysis. Standardized coefficients were used to measure and compare effect sizes.

RESULTS

Fetal growth, head, and somatic postnatal growth were significant independent predictors of cognition at age 10. These associations remained even among children born within the normal birth-weight range and those who did not experience neonatal problems. Effect of head size on cognition was greater than the effect of birth weight. Weight at 10 had a small negative effect on cognition. Gestational age was not directly associated with cognitive function, but it had a weak indirect effect. Parent's socioeconomic status was strongly associated with child's cognitive function.

CONCLUSION

Although effect sizes of prenatal and postnatal growth on cognition are modest compared with the strong effect size of social factors, they might have greater impact at the population level, since most children are born without low birth weight.

Risks for low intellectual performance related to being born small for gestational age are modified by gestational age

OBJECTIVE

We sought to study whether the association between being born small for gestational age and risk for low intellectual performance was modified by gestational age.

METHODS

A population-based cohort study was conducted of 352,125 boys who were born between 28 and 43 completed weeks of gestation from 1973 to 1981 in Sweden. Risk for low intellectual performance at military conscription, estimated as odds ratios with 95% confidence intervals was measured.

RESULTS

Compared with men who were born preterm (28-36 weeks) and had normal birth weight for gestational age, men who were born preterm and had a very low birth weight for gestational age were not at increased risk for low intellectual performance. In contrast, men who were born preterm with a very short birth length or a very small head circumference for gestational age faced a near doubled risk for low intellectual performance compared with their appropriate peers. Among men who were born at term (37-41 weeks), risk for low intellectual performance was increased among those with very or moderately small birth weight, birth length, or head circumference for gestational age.

CONCLUSIONS

During early stages of gestation, growth in length and head circumference may be more important for intellectual development than weight increase. Future studies on size at birth and intellectual performance should consider also including anthropometric measurements other than birth weight.

Cerebral MRI findings in very-low-birth-weight and small-for-gestational-age children at 15 years of age

BACKGROUND

A high prevalence of abnormal cerebral MRI findings has been reported in low-birth-weight children.

OBJECTIVE

To compare MRI findings in very-low-birth-weight (VLBW) and term small-for-gestational-age (SGA) children with controls in early adolescence.

MATERIALS AND METHODS

Cerebral MRI was used to examine 55 VLBW, 54 SGA and 66 controls at 15 years of age. The MR images were qualitatively assessed, and size of ventricles, white-matter and grey-matter abnormalities were reported.

RESULTS

The VLBW teenagers had a higher prevalence of various MRI abnormalities than SGA children and controls. Dilation of the ventricular system, especially of the occipital horns, was found in 82% of the VLBW group, in 19% of the SGA group and in 21% of controls. White-matter reduction was found in 53% of the VLBW, in 6% of the SGA and in 2% of controls. Corpus callosum thinning was found in 47% of the VLBW, in 2% of the SGA and in 6% of controls. Periventricular gliosis was found in 29% of the VLBW, in 4% of the SGA and in 8% of controls.

CONCLUSIONS

Cerebral MRI pathology in white matter is a common finding in VLBW teenagers. The findings may indicate minor perinatal PVL with resulting loss of white-matter tissue and ventricular dilation.

Growth in early life and childhood IQ at age 11 years: the Newcastle Thousand Families Study

BACKGROUND

It has been suggested that in addition to genetic factors, fetal and post-natal growth influence childhood cognition, although it is unclear whether such an effect continues throughout childhood. This study aimed at investigating the potential relationships between childhood IQ at age 11 years and birth weight and height at the ages of 9 and 13 years, after adjusting for the confounding factors available to this investigation.

METHODS

The Newcastle Thousand Families study, a prospectively followed cohort, originally consisted of all 1142 births in the city of Newcastle in May and June 1947. Using data on 733 members of this cohort, we investigated the associations between IQ at age 11, and birth weight and height at ages 9 and 13 years.

RESULTS

Birth weight showed no association with childhood IQ. However, height at age 9 years was a significant predictor of childhood IQ after adjusting for socioeconomic status (standardized regression coefficient b = 2.6, 95% CI 1.6-3.6, P < 0.0001). Height at age 13 was also a significant predictor of IQ after adjusting for socioeconomic status (b = 3.4, 95% CI 2.3-4.4, P = 0.001), and explained an additional 2.5% of the variation in IQ scores to that already explained by socioeconomic status and height at age nine.

CONCLUSIONS

These results suggest a continuing effect of post-natal growth on childhood cognition beyond the age of 9 years. Post-natal growth, which may be influenced by genetic factors and nutrition and socioeconomic circumstances in childhood, may be more important than fetal growth in terms of childhood cognition.

Current concepts in intrauterine growth restriction

Regulation of fetal growth is multifactorial and complex. Diverse factors, including intrinsic fetal conditions as well as maternal and environmental factors, can lead to intrauterine growth restriction (IUGR). The interaction of these factors governs the partitioning of nutrients and rate of fetal cellular proliferation and maturation. Although IUGR is probably a physiologic adaptive response to various stimuli, it is associated with distinct short- and long-term morbidities. Immediate morbidities include those associated with prematurity and inadequate nutrient reserve, while childhood morbidities relate to impaired maturation and disrupted organ development. Potential long-term effects of IUGR are debated and explained by the fetal programming hypothesis. In formulating a comprehensive approach to the management and follow-up of the growth-restricted fetus and infant, physicians should take into consideration the etiology, timing, and severity of IUGR. In addition, they should be cognizant of the immediate perinatal response of the growth-restricted infant as well as the childhood and long-term associated morbidities. A multi disciplinary approach is imperative, including early recognition and obstetrical management of IUGR, assessment of the growth-restricted newborn in the delivery room, possible monitoring in the neonatal intensive care unit, and appropriate pediatric follow-up. Future research is necessary to establish effective preventive, diagnostic, and therapeutic strategies for IUGR, perhaps affecting the health of future generations.

Long term cognitive development in children with prolonged crying

BACKGROUND

Long term studies of cognitive development and colic have not differentiated between typical colic and prolonged crying.

OBJECTIVE

To evaluate whether colic and excessive crying that persists beyond 3 months is associated with adverse cognitive development.

DESIGN

Prospective cohort study. A sample of 561 women was enrolled in the second trimester of pregnancy. Colic and prolonged crying were based on crying behaviour assessed at 6 and 13 weeks. Children's intelligence, motor abilities, and behaviour were measured at 5 years (n = 327). Known risk factors for cognitive impairment were ascertained prenatally, after birth, at 6 and 13 weeks, at 6, 9, and 13 months, and at 5 years of age.

RESULTS

Children with prolonged crying (but not those with colic only) had an adjusted mean IQ that was 9 points lower than the control group. Their performance and verbal IQ scores were 9.2 and 6.7 points lower than the control group, respectively. The prolonged crying group also had significantly poorer fine motor abilities compared with the control group. Colic had no effect on cognitive development.

CONCLUSIONS

Excessive, uncontrolled crying that persists beyond 3 months of age in infants without other signs of neurological damage may be a marker for cognitive deficits during childhood. Such infants need to be examined and followed up more intensively.

Behavioral and social development of children born extremely premature: 5-year follow-up

A cohort of extremely prematurely born children and matched term controls was assessed at 5 years of age. The parents completed a questionnaire on their behavioral and social development. The purpose was to illuminate whether the children's general intellectual ability and parental sensitivity were associated with behavioral and social development. The index children exhibited more hyperactive behavior and had poorer social skills than the controls. Lower Full Scale IQ (FSIQ) was associated with outward reacting and hyperactive behavior and poorer social skills. Sensitive parenting was associated with less outward reacting and less hyperactive behavior. When controlling for differences in FSIQ and parental sensitivity, the index children persisted to have an increased risk of exhibiting hyperactive behavior but not poorer social skills. The index children with normal intellectual development, however, did not exhibit more behavioral problems or poorer social skills than the control children did.

Neurodevelopmental outcome at 8 months and 4 years among infants born full-term small-for-gestational-age

OBJECTIVES

To examine the association between intrauterine growth restriction and neurodevelopmental outcome among full-term small-for-gestational-age (SGAT) infants at 8 months and 4 years of age.

STUDY DESIGN

Growth parameters at birth and test scores on measures of neurodevelopmental function for 3922 children born SGAT were compared with those of 29,369 children born appropriately grown-for-gestational-age term from similar economic backgrounds. Additional within-SGAT/economic group comparisons were made for 1684 SGAT infants with symmetric undergrowth at birth and 2034 SGAT infants with asymmetric undergrowth at birth.

RESULTS

Regardless of socioeconomic background, infants born SGAT were found to be at significantly increased risk for neurodevelopmental difficulties at 8 months and at 4 years of age. Few within SGAT/socioeconomic group differences in neurodevelopmental outcome appeared to be associated with specific pattern of growth restriction at birth.

CONCLUSIONS

The present findings provide further evidence of the individual and public health impact of SGAT birth.

Long term outcome of small versus appropriate size for gestational age co-twins/triplets

BACKGROUND

Small for gestational age (SGA) extremely low birthweight (ELBW < 1000 g) survivors often remain small and/or have subnormal school performance. Some are twins/triplets with larger appropriate size for gestational age (AGA) co-twins/triplets.

OBJECTIVE

To assess whether SGA ELBW twins/triplets remain different from their AGA co-twins/triplets.

DESIGN, SETTING

During 1981-1999, 353 SGA ELBW neonates were admitted to our neonatal intensive care unit: 267 survived, 54/267 were twins/triplets, and 36/54 had AGA surviving co-twins/triplets. This longitudinal study describes the growth, neurodevelopmental outcome, and school performance of these 36 sets (3-17 years). The children were classified as normal, or having minor, moderate, or severe deficiencies.

RESULTS

Values for birth weight (mean intrapair z score difference 2.26), length (2.74), and head circumference (2.62) were lower in SGA neonates than in AGA co-twins/triplets. SGA survivors remained smaller at 3-6 years of age: mean intrapair z score difference in weight, 1.37, height, 1.54, head circumference, 1.21. From 6 to 17 years, smaller differences persisted. Former SGA children had a tendency to have motor deficiencies (nine SGA v three AGA) and mental retardation (seven v four), same hearing loss (two v two), but significantly more visual abnormalities (15 v 11), behavioural disturbances (14 v five), and speech problems (14 v eight). Twenty four sets were in the same normal level class, often supported by familial/professional help.

CONCLUSIONS

Although raised in the same environment, SGA ELBW survivors remained smaller and had more visual/behavioural/speech problems, but most maintained grade level parity with their AGA siblings, with appropriate help.

Psychosocial intervention improves the development of term low-birth-weight infants

It is estimated that 11% of births in developing counties are term low-birth-weight (LBW); however, there is limited information on the development of these infants. Our objectives were to determine the effect of psychosocial intervention on the development of LBW infants and to compare term LBW and normal-birth-weight (NBW) infants. Term LBW (n = 140) and NBW infants (n = 94) were enrolled from the main maternity hospital in Kingston, Jamaica. The LBW infants were randomly assigned to control or intervention comprising weekly home visits from birth to 8 wk and from 7 to 24 mo of age. Development was assessed at 15 and 24 mo with the Griffiths Scales. The intervention benefited the infants' developmental quotient (DQ, P < 0.05) and performance subscale at 15 mo (P < 0.02), the hand and eye (P < 0.05) and performance subscales (P < 0.02) at 24 mo, and home environment at 12 mo. The effect of the intervention on development was mediated in part by the improvement in the home environment. The control LBW infants had significantly lower scores than the NBW in DQ and several subscales, whereas there were no significant differences between the NBW and the LBW infants after intervention. In conclusion, term LBW was associated with developmental delays, which were reduced with psychosocial intervention.

Cognitive and motor development among small-for-gestational-age infants: impact of zinc supplementation, birth weight, and caregiving practices

OBJECTIVE

Infants who are born small for gestational age (SGA) are at risk for developmental delays, which may be related to deficiencies in zinc, an essential trace metal, or to deficiencies in their ability to elicit caregiver responsiveness (functional isolation hypothesis). The objective of this study was to evaluate at 6 and 10 months of age the impact of a 9-month supplementation trial of 5 mg of zinc on the development and behavior of infants who were born SGA and to evaluate infants' ability to elicit responsive caregiver behavior.

METHODS

A randomized, controlled trial of zinc supplementation was conducted among 200 infants in a low-income, urban community in Delhi, India. Infants were recruited when they were full term (>36 weeks) and SGA (birth weight <10th percentile weight-for-gestational age). Infants were randomized to receive daily supplements of a micronutrient mix (folate, iron, calcium, phosphorus, and riboflavin) with or without 5 mg of zinc sulfate. The supplement was administered by field workers daily from 30 days to 9 months of age. At 6 and 10 months, infant development and behavior were measured in a clinical setting using the Bayley Scales of Infant Development II. Caregiver responsiveness, observed on an Indian version of the Home Observation for Measurement of the Environment scale, was measured during a home visit at 10 months. During both the clinic and home visits, caregivers reported on their infant's temperament.

RESULTS

There were no direct effects of zinc supplementation on the infants' development or behavior at either 6 or 10 months. In a subgroup analysis among the zinc-supplemented infants, lower birth weight infants were perceived to be more temperamentally difficult than higher weight infants; in the control group, birth weight was not associated with temperament. Heavier birth weight infants had better scores on all measures of development and behavior at 6 months and on changes in mental and motor development from 6 to 10 months, compared with lighter birth weight infants. Boys had better weight gain and higher scores on mental development and emotional regulation than girls. Infants who were from families of higher socioeconomic status (indexed by parental education, house size, and home ownership) had higher scores on mental development and orientation/engagement (exploratory behavior) than infants who were from families of lower socioeconomic status. In keeping with the functional isolation hypothesis, caregiver responsiveness was associated with infant irritability, controlling for socioeconomic status, gender, birth weight, and weight gain. Responsive mothers were more likely to perceive their infants to be temperamentally easy than less responsive mothers.

CONCLUSION

Possible explanations for the lack of effects of zinc supplementation on infant development and behavior include 1) subtle effects of zinc supplementation that may not have been detected by the Bayley Scales, 2) interference with other nutritional deficiencies, or 3) no impact of zinc deficiency on infants' development and behavior. The link between birth weight and irritability among infants in the zinc supplementation group suggests that the response to zinc supplementation may differ by birth weight, with irritability occurring among the most vulnerable infants. Longer term follow-up studies among zinc-supplemented infants are needed to examine whether early supplementation leads to developmental or behavioral changes that have an impact on school-age performance. The relationship between infant irritability and low maternal responsiveness lends support to the functional isolation hypothesis and the importance of asking caregivers about infant temperament.

Earlier smoking habits are associated with higher serum lipids and lower milk fat and polyunsaturated fatty acid content in the first 6 months of lactation

OBJECTIVE

To investigate the relation between maternal smoking habits, plasma lipids and milk fatty acid (FA) content and composition.

DESIGN

Breastfeeding mothers who gave birth to healthy, full-term infants were recruited. Mothers were interviewed on smoking habits, being defined smokers (S) when usually smoking at least five cigarettes per day before pregnancy.

SETTING

Department of Pediatrics, San Paolo Hospital, Milan, Italy.

SUBJECTS

In total, 92 mothers: 61 non-S (NS) and 31 S.

INTERVENTIONS

Pooled hindmilk was collected at the first raise of milk (colostrum stage), 1, 3 and 6 months, and total lipid (TL) content and fatty acid (FA) composition were evaluated. Maternal dietary habits were assessed by a food-frequency questionnaire. Two subsamples (16 NS, 6 S) were investigated after delivery and at 3 months for serum lipids and FA status. At 6 months after delivery, the number of mothers still breastfeeding decreased to 30. Variables were compared using nonparametric tests.

RESULTS

In smoking mothers serum levels of triglycerides, cholesterol and low-density lipoproteins were higher, while those of high-density lipoproteins were lower. TL content in breast milk was similar in the two groups just after delivery but higher in milk from NS at 1 month. TL content and FA absolute amounts of linoleic, arachidonic, alpha-linolenic and docosahexaenoic (DHA) acid in breast milk were lower in S vs NS 1 month after delivery. Also 3 months after delivery, the breast milk of smoking mothers contained less DHA than the breast milk of nonsmoking mothers.

CONCLUSIONS

Maternal cigarette smoking in early pregnancy is associated with higher plasma lipid levels and lower milk TL and DHA content in the first months of lactation.

Birth weight, childhood socioeconomic environment, and cognitive development in the 1958 British birth cohort study

OBJECTIVES

To examine the combined effect of social class and weight at birth on cognitive trajectories during school age and the associations between birth weight and educational outcomes through to 33 years.

DESIGN

Longitudinal, population based, birth cohort study.

PARTICIPANTS

10 845 males and females born during 3-9 March 1958 with information on birth weight, social class, and cognitive tests.

MAIN OUTCOME MEASURES

Reading, maths, draw a man, copying designs, verbal and non-verbal ability tests at ages 7, 11, and 16, highest qualifications achieved by 33, and trajectories of maths standardised scores at 7-16 years.

RESULTS

The outcome of all childhood cognitive tests and educational achievements improved significantly with increasing birth weight. Analysis of maths scores at 7 and of highest qualifications achieved by 33 showed that the relations were robust to adjustment for potential confounding factors. For each kilogram increase in birth weight, maths z score increased by 0.17 (adjusted estimate 0.15, 95% confidence interval 0.10 to 0.21) for males and 0.21 (0.20, 0.14 to 0.25) for females. Trajectories of maths z scores between 7 and 16 years diverged for different social class groups: participants from classes I and II increased their relative position on the score with increasing age, whereas classes IV and V showed a relative decline with increasing age. Birth weight explained much less of the variation in cognition than did social class (range 0.5-1.5% v 2.9-12.5%).

CONCLUSIONS

The postnatal environment has an overwhelming influence on cognitive function through to early adulthood, but these strong effects do not explain the weaker but independent association with birth weight.

Neuropsychologic and motor function in small-for-gestation preschoolers

The aim of this study was to evaluate neuropsychologic and motor performance in term small-for-gestation preschool children. A patient-based sample of 311 5-year-old children with birth weights less than the fifteenth percentile for gestation was compared with a random sample of 321 appropriate-for-gestation control subjects. The main assessment tools were subscales from the Wechsler Preschool and Primary Scale of Intelligence Revised, subscales from the Illinois Test of Psycholinguistic Abilities, tests of manual dexterity and figure copying, and the Peabody Developmental Motor Scales. The small-for-gestation children had mean scores on tests of visuospatial and visuomotor abilities that were one fourth standard deviation lower than appropriate-for-gestation control subjects and slightly lower scores on manual dexterity. The small-for-gestation children were comparable to appropriate-for-gestation children regarding motor performance. We therefore conclude that the neuropsychologic and neuromotor performance in preschool years of term small-for-gestation children is reassuring.

Behavior in term, small for gestational age preschoolers

AIMS

To evaluate whether being born small for gestational age (SGA) was associated with an increased frequency of preschool behavioral problems.

STUDY DESIGN

Follow-up study at 5 years of age.

SUBJECTS

A population based cohort of 318 term infants who were SGA, defined as having a birthweight less than the 15th percentile for gestational age, and without major handicap such as cerebral palsy or mental retardation, and a random control sample of 307 appropriate for gestational age (AGA) infants.

OUTCOME MEASURES

The Personality Inventory for Children and the Yale Children's Inventory (completed by the mothers), and child behavior during psychometric testing.

RESULTS

Behavior problems was not more common among the SGA children. The results were not confounded by a wide range of parental demographic and child rearing factors, including maternal non-verbal problem solving abilities, child rearing style, and maternal psychological distress. However, the parental factors explained 13% of the variance in a summary score of child behavior compared to 1% explained by SGA vs. AGA status. The SGA children were not more sensitive to the negative impacts of parental risk factors than AGA controls. The study does not address the outcome of severely growth-retarded SGA infants.

CONCLUSION

Being born moderately SGA is not a significant risk factor for preschool behavior problems.