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Abstract
Aim To investigate whether infants born late-preterm have poorer school attainment compared to those born at term.
Methods This study used data from the Avon Longitudinal Study of Parents and Children. Key stage one (KS1) school assessment results were obtained from local education authorities. Logistic regression models were used to investigate the effect of gestation, that is, late-preterm (32–36 weeks) versus term (37–41 weeks), on success in KS1 teacher assessments. Regression models were adjusted for potential confounders, including maternal education and markers of socioeconomic status.
Results There were 12 089 term infants and 734 late-preterm infants. 71% of late-preterm children were successful in KS1 assessments compared to 79% of those born at term (OR 0.64 (95% CI 0.53 to 0.78); p<0.001). This difference persisted on adjusting for potential confounders (OR 0.74 (95% CI 0.59 to 0.92); p=0.007).
Conclusions Children born late-preterm are less likely to be successful in early school assessments than those born at term. This group of vulnerable children warrants closer surveillance for early identification of potential educational failure.
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Introduction
Preterm birth, defined as less than 37 weeks gestation, is associated with poor long-term cognitive and neurological outcomes. Much previous research has focused on those born extremely (<28 weeks) or very (<32 weeks) preterm. However, far less is known about these outcomes in preterm infants born after 32 weeks gestation, generally referred to as ‘late-preterm’ infants. Infants born at 32–36 weeks make up 6% of all live births and 82% of all preterm births in the UK. A report by the American Academy of Pediatrics in 2007 highlighted this group of late-preterm infants as a ‘population at risk’, while acknowledging a lack of research demonstrating long-term medical, neurological and developmental outcomes.1
Studies have shown an increased risk of developmental delay, cerebral palsy and learning difficulties in late-preterm infants compared to term,2 3 as well as poorer school outcomes.4,–,6 However, there is currently a paucity of information about school attainment among children born late-preterm within the UK school and healthcare systems. We therefore investigated early school attainment within the Avon Longitudinal Study of Parents and Children (ALSPAC), testing the hypothesis that children born late-preterm will have poorer school outcomes compared to those born at term.
Methods
This study used data from the ALSPAC, which recruited pregnant women due to deliver in 1991 and 1992 in Avon, UK.7 The original cohort comprised 14 541 pregnancies, which resulted in 14 062 live births and 13 988 infants alive at 1 year of age.
Gestational age was retrieved from computerised medical records. Of the 13 978 infants alive at 1 year for whom data were available, 111 (<1%) were born at <32 weeks, 734 (5%) were born at 32–36+6 weeks, 12 089 (86%) were born at 37–41+6 weeks and 1044 (7%) were born at ≥42 weeks gestation. Children were classified as ‘late-preterm’ if born between 32 and 36+6 weeks gestation, or ‘term’ if born between 37 and 41+6 weeks gestation. Infants born at <32 weeks or ≥42 weeks were excluded.
In England, children in state-funded schools follow a set national teaching curriculum from 5 years of age, with progression through the school system divided into four ‘key stages’. Key stage one (KS1) comprises school years one and two (ages 5–7 years), with teacher assessments in reading, writing and mathematics taken at the end of year two. Progress is reported in terms of ‘national curriculum levels’. At KS1, most children work between levels 1 and 3, with a target level of 2 in the KS1 assessment.
Data on KS1 assessments were obtained from the local education authorities (LEAs) covering the former Avon region. The results for the three assessment domains (reading, writing and mathematics) were dichotomised, with success defined as achieving at least level 2, the expected level of attainment. The primary outcome was overall assessment success, defined as achieving at least level 2 in all three domains. Secondary outcomes were success in the individual subjects.
Logistic regression models were used to investigate the effect of gestation (late-preterm vs term) on school attainment, as measured by binary KS1 results. Regression models were adjusted for possible confounders, which included child factors, maternal/perinatal factors and markers of socioeconomic status.
Multiple imputation by chained equations was used to impute missing covariate data. Prespecified subgroup analyses were conducted for gender, parental social class, maternal education and ethnicity; the interaction effects of these variables were tested.
Sensitivity analyses included a complete-case analysis, and analyses following imputation of outcome data as well as predictor variables. Additionally, analyses were repeated including only infants born by vaginal delivery, with a birth weight within 1 SD of the mean for gestation, to look for any difference in effect among ‘healthy’ late-preterm infants. Finally, analyses were repeated limiting the ‘late-preterm’ group to those born between 34 and 36+6 weeks gestation.
Analyses were conducted using Stata version 11.
Ethics approval was obtained from the ALSPAC Law and Ethics Committee and the Local Research Ethics Committees.
Results
Baseline characteristics
There were 12 089 (86% of the ALSPAC cohort) term infants and 734 (5%) late-preterm infants. Of the 734 late-preterm infants, 111 (15%) were born at 32–33 weeks gestation, and 623 (85%) were born at 34–36 weeks. The majority of term and late-preterm infants were from a white ethnic background. Late-preterm infants had lower birth weights and lengths, and were more likely to be male (57% vs 51%; p=0.02). Additionally, late-preterm infants were more likely to be from a multiple pregnancy (19% vs 2%; p<0.001) and born by caesarean section (23% vs 10%; p<0.001). Mothers of late-preterm infants tended to have less qualifications and lower incomes.
Gestation and school attainment
Children born late-preterm were less likely to be successful in KS1 assessments overall, as well as in each subject area (table 1). Following adjustment for confounders, the OR attenuated slightly (table 2).
Proportion of successful students in key stage one tests
Logistic regression for key stage one test scores
Subgroup analyses
There was no evidence of an interaction of parental social class, maternal education or ethnicity with the relationship between gestation and school outcome. There was some evidence to suggest a greater association between late-prematurity and school attainment among females compared to males (OR for overall score 0.56 for females vs 0.86 for males; pinteraction=0.034).
Sensitivity analyses
Complete-case analysis produced similar results to those following multiple imputation. Limiting the analyses to normal deliveries with a birth weight within 1 SD of the mean again gave similar results. Imputing the outcome variables as well as covariates did not change the findings, nor did restricting the late-preterm group to 34–36 weeks.
Discussion
This study has demonstrated that infants born between 32 and 36 weeks gestation are less likely to achieve the expected level in teacher assessments at age 7 than children born at term. This finding was unchanged on including only those born at 34 weeks or later, and appears to persist even among infants born by vaginal delivery with an appropriate birth weight. This suggests the difference found between late-preterm and term children is not solely attributable to greater effects in lower gestation infants, in those with growth restriction or by mode of delivery.
A major strength of this study is the use of data from a large, population-based UK cohort with detailed data collected longitudinally. Linkage to LEA databases enabled use of standardised national tests as an objective outcome measure. A limitation of the study is missing data, and the subsequent potential for bias. However, approximately 80% of our sample had outcome data available, and we imputed missing covariate data using multiple imputation, minimising bias and loss of precision. Further, sensitivity analyses imputing both outcome and covariate data did not significantly alter the results.
The findings of this study agree with previous studies suggesting poorer school outcomes in late-preterm infants4,–,6 and add to an emerging evidence base of poor long-term neurological and developmental outcomes among children born late-preterm.2 3
Given that children born late-preterm make up the majority of all preterm births, and comprise around 5% of the population, this group warrants more recognition and surveillance than is currently provided. We recommend children born late-preterm receive a ‘school readiness’ and educational assessment prior to starting school to help identify potential learning problems. Early intervention within this vulnerable group of children may help reduce the burden of school problems and their associated consequences.
What is already known on this topic
▶ Extreme or very preterm birth is associated with poor long-term neurological and cognitive outcomes.
▶ Studies are beginning to demonstrate poorer outcomes among late-preterm infants, previously deemed ‘near term’ and thought to be at relatively low risk.
What this study adds
▶ Late-preterm infants are less likely to succeed in early school assessments compared to their peers born at term.
▶ Children born late-preterm warrant closer surveillance than is currently provided for in order to identify potential learning problems early.
Acknowledgments
The authors are extremely grateful to all the families who took part in this study, the midwives for their help in recruiting them, and the entire ALSPAC team, which includes interviewers, computer and laboratory technicians, clerical workers, research scientists, volunteers, managers, receptionists and nurses.
Footnotes
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Funding The UK Medical Research Council (grant ref: 74882), the Wellcome Trust (grant ref: 076467) and the University of Bristol provide core support for ALSPAC. This publication is the work of the authors and PJP will serve as guarantor for the contents of this paper. No separate funding was obtained for this analysis. PJP is supported by a National Institute for Health Research (NIHR) Academic Clinical Fellowship.
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Competing interests None.
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Ethics approval The ALSPAC Law and Ethics Committee and the Local Research Ethics Committees approved this study.
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Provenance and peer review Not commissioned; externally peer reviewed.