Gestational age at birth and academic performance: population-based cohort study

Poor socioeconomic outcomes: Completion of the final examination after lower secondary education mitigates risks associated with gestational age

AIM

To investigate the influence of gestational age (GA) on the association between completion of the final examination after 10-11 years of basic education and education, financial independence and income in early adulthood.

METHODS

A nationwide register-based study including individuals born in Denmark between 1990 and 1992. Completion of the examination was evaluated at age 18 and education, financial independence and income at age 28.

RESULTS

Of 165 683 individuals included, 15.7%, 10.8% and 5.5% had low educational level, were not financially independent and had low income. For those who completed the examination odds ratio (OR) ranged from 1.03 at GA = 32-36 weeks to 1.25 at ≤27 weeks for low education, from 1.10 to 0.91 for not being financial independent and from 1.06 to 1.48 for low income. For those who did not complete the examination, OR increased from 7.55 at ≥37 weeks to 15.03 at ≤27 weeks for low education and from 4.68 to 15.31 for not being financial independent. For low income, OR was 2.57 and independent of GA.

CONCLUSION

For individuals who completed the examination, the odds of poor socioeconomic outcomes were independent of GA. Individuals who did not complete the examination had increased odds of poor socioeconomic outcomes, particularly as GA decreased.

Preterm children born below 33-35 weeks of gestation have an increased risk of mathematical difficulties

AIM

To investigate the association between gestational age (GA) and grade point averages by domains of language and mathematics at the end of lower secondary education.

METHODS

A nationwide register-based study including all Danish children born in 1992-1997 who completed lower secondary education. Grades were evaluated by GA. Domain-specific differences in grades were investigated, and academic profiles were made.

RESULTS

The study population comprised 319 796 children. For language, only minor differences in grades were observed. The grades in mathematics ranged from 7.02 (95% confidence interval [CI]: 7.00-7.04) at GA = 40 weeks to 5.86 (95% CI: 5.61-6.11) at GA <28 weeks. Grade differences showed lower grades in mathematics, compared to language, below GA 33-35 weeks. The academic profile of mathematical difficulties was more prevalent among GA <32 weeks. Average/high grades within both domains represented the predominant academic profile, constituting 68.8% at GA 39-41 weeks and 56.6% at GA <28 weeks.

CONCLUSION

Only in mathematics decreasing GA was associated with lower grades. Increased mathematical difficulties were found below GA 33-35 weeks. The academic profile of mathematical difficulties was more prevalent among GA <32 weeks. However, the absolute differences in grades were small, and the predominant academic profile was average/high grades within both domains across all GA.

Gestational age at birth and cognitive outcomes in adolescence: population based full sibling cohort study

OBJECTIVE

To investigate the association between gestational age at birth and cognitive outcomes in adolescence.

DESIGN

Nationwide population based full sibling cohort study.

SETTING

Denmark.

PARTICIPANTS

1.2 million children born between 1 January 1986 and 31 December 2003, of whom 792 724 had one or more full siblings born in the same period.

MAIN OUTCOME MEASURES

Scores in written language (Danish) and mathematics examinations as graded by masked assessors at the end of compulsory schooling (ninth grade, ages 15-16 years), in addition to intelligence test score at military conscription (predominantly at age 18 years) for a nested sub-cohort of male adolescents. School grades were standardised as z scores according to year of examination, and intelligence test scores were standardised as z scores according to year of birth.

RESULTS

Among 792 724 full siblings in the cohort, 44 322 (5.6%) were born before 37+0 weeks of gestation. After adjusting for multiple confounders (sex, birth weight, malformations, parental age at birth, parental educational level, and number of older siblings) and shared family factors between siblings, only children born at <34 gestational weeks showed reduced mean grades in written language (z score difference -0.10 (95% confidence interval -0.20 to -0.01) for ≤27 gestational weeks) and mathematics (-0.05 (-0.08 to -0.01) for 32-33 gestational weeks, -0.13 (-0.17 to -0.09) for 28-31 gestational weeks, and -0.23 (-0.32 to -0.15) for ≤27 gestational weeks), compared with children born at 40 gestational weeks. In a nested sub-cohort of full brothers with intelligence test scores, those born at 32-33, 28-31, and ≤27 gestational weeks showed a reduction in IQ points of 2.4 (95% confidence interval 1.1 to 3.6), 3.8 (2.3 to 5.3), and 4.2 (0.8 to 7.5), respectively, whereas children born at 34-39 gestational weeks showed a reduction in intelligence of <1 IQ point, compared with children born at 40 gestational weeks.

CONCLUSIONS

Cognitive outcomes in adolescence did not differ between those born at 34-39 gestational weeks and those born at 40 gestational weeks, whereas those with a gestational age of <34 weeks showed substantial deficits in multiple cognitive domains.

Association of Gestational Age at Birth With Subsequent Neurodevelopment in Early Childhood: A National Retrospective Cohort Study in China

BACKGROUND

The association between preterm birth and neurodevelopmental delays have been well examined, however, reliable estimates for the full range of gestational age (GA) are limited, and few studies explored the impact of post-term birth on child development.

OBJECTIVE

This study aimed to examine the long-term neuropsychological outcomes of children born in a full range of GA with a national representative sample in China.

METHODS

In this retrospective population-based cohort study, a total of 137,530 preschoolers aged 3-5 years old (65,295/47.5% females and 72,235/52.5% males) were included in the final analysis. The Ages and Stages Questionnaires-Third Edition (ASQ-3) was completed by parents to evaluate children's neurodevelopment. The associations between GA and neurodevelopment were analyzed by a generalized additive mixed model with thin plate regression splines. Logistic regression was also conducted to examine the differences in children's development with different GAs.

RESULTS

There was a non-linear relationship between GA and children's neurodevelopmental outcomes with the highest scores at 40 weeks gestational age. The adjusted risks of GAs (very and moderately preterm, late-preterm, early-term, and post-term groups) on suspected developmental delays were observed in communication (OR were 1.83, 1.28, 1.13, and 1.21 respectively, each p < 0.05), gross motor skill (OR were 1.67, 1.38, 1.10, and 1.05 respectively, each p < 0.05), and personal social behavior (OR were 1.01, 1.36, 1.12, and 1.18 respectively, each p < 0.05). The adjusted OR of very and moderately preterm, late-preterm, and early-term were observed in fine motor skills (OR were 1.53, 1.22, and 1.09 respectively, each p < 0.05) and problem-solving (OR were 1.33, 1.12, and 1.06 respectively, each p < 0.05).

CONCLUSION

GAs is a risk factor for neurodevelopmental delays in preschoolers after controlling for a wide range of covariates, and 40-41 weeks may be the ideal delivery GA for optimal neurodevelopmental outcomes. Close observation and monitoring should be considered for early- and post-term born children as well as pre-term children.

Effect of nutritionally modified infant formula on academic performance: linkage of seven dormant randomised controlled trials to national education data

OBJECTIVE

To compare differences in academic performance between adolescents who were randomised in infancy to modified or standard infant formula.

DESIGN

Linkage of seven dormant randomised controlled trials to national education data.

SETTING

Five hospitals in England, 11 August 1993 to 29 October 2001, and schools in England, September 2002 to August 2016.

PARTICIPANTS

1763 adolescents (425 born preterm, 299 born at term and small for gestational age, 1039 born at term) who took part in one of seven randomised controlled trials of infant formula in infancy.

INTERVENTIONS

Nutrient enriched versus standard term formula (two trials), long chain polyunsaturated fatty acid (LCPUFA) supplemented versus unsupplemented formula (two trials), high versus low iron follow-on formula (one trial), high versus low sn-2 palmitate formula (one trial), and nucleotide supplemented versus unsupplemented formula (one trial).

MAIN OUTCOME MEASURES

The primary outcome, determined by linkage of trial data to school data, was the mean difference in standard deviation scores for mandated examinations in mathematics at age 16 years. Secondary outcomes included differences in standard deviation scores in English (16 and 11 years) and mathematics (11 years). Analysis was by intention to treat with multiple imputation for participants missing the primary outcome.

RESULTS

1607 (91.2%) participants were linked to school records. No benefit was found for performance in mathematics examinations at age 16 years for any modified formula: nutrient enriched in preterm infants after discharge from hospital, standard deviation score 0.02 (95% confidence interval -0.22 to 0.27), and nutrient enriched in small for gestational age term infants -0.11 (-0.33 to 0.12); LCPUFA supplemented in preterm infants -0.19 (-0.46 to 0.08) and in term infants -0.14 (-0.36 to 0.08); iron follow-on formula in term infants -0.12 (-0.31 to 0.07); and sn-2 palmitate supplemented formula in term infants -0.09 (-0.37 to 0.19). Participants from the nucleotide trial were too young to have sat their General Certificate of Secondary Education (GCSE) examinations at the time of linkage to school data. Secondary outcomes did not differ for nutrient enriched, high iron, sn-2 palmitate, or nucleotide supplemented formulas, but at 11 years, preterm and term participants randomised to LCPUFA supplemented formula scored lower in English and mathematics.

CONCLUSIONS

Evidence from these randomised controlled trials indicated that the infant formula modifications did not promote long term cognitive benefit compared with standard infant formulas.

Infant formula composition and educational performance: a protocol to extend follow-up for a set of randomised controlled trials using linked administrative education records

INTRODUCTION

The effect of infant nutrition on long-term cognition is important for parents and policy makers. However, most clinical trials typically have short follow-up periods, when measures of cognition are poorly predictive of later function. The few trials with longer-term follow-up have high levels of attrition, which can lead to selection bias, and in turn to erroneous interpretation of long-term harms and benefits of infant nutrition. We address the need for unbiased, long-term follow-up, by linking measures of educational performance from administrative education records. Educational performance is a meaningful marker of cognitive function in children and it is strongly correlated with IQ. We aim to evaluate educational performance for children who, as infants, were part of a series of trials that randomised participants to either nutritionally modified infant formula or standard formula. Most trialists anticipated positive effects of these interventions on later cognitive function.

METHODS AND ANALYSIS

Using data from 1923 participants of seven randomised infant formula trials linked to the English National Pupil Database (NPD), this study will provide new insights into the effect of nutrient intake in infancy on school achievement. Our primary outcome will be the mean differences in z-scores between intervention and control groups for a compulsory Mathematics exam sat at age 16. Secondary outcomes will be z-scores for a compulsory English exam at age 16 and z-scores for compulsory Mathematics and English exams at age 11. We will also evaluate intervention effects on the likelihood of receiving special educational needs (SEN) support. All analyses will be performed separately by trial.

ETHICS AND DISSEMINATION

Research ethics approval, and approval from the Health Research Authority Confidentiality Advisory Group, has been obtained for this study. The results of this study will be disseminated to scientific, practitioner, and lay audiences, submitted for publication in peer-reviewed journals, and will contribute towards a PhD dissertation.

Does Birth Trigger Cell Death in the Developing Brain?

Developmental cell death eliminates half of the neurons initially generated in the mammalian brain, and occurs perinatally in many species. It is possible that the timing of neuronal cell death is developmentally programmed, and only coincidentally associated with birth. Alternatively, birth may play a role in shaping cell death. To test these competing hypotheses, we experimentally advanced or delayed birth by 1 d in mice (within the normal range of gestation for the species) and examined effects on the temporal pattern and magnitude (amount) of neuronal cell death, using immunohistochemical detection of activated caspase-3 as a cell death marker. In order to detect effects of subtle changes in birth timing, we focused on brain areas that exhibit sharp postnatal peaks in cell death. We find that advancing birth advances peak cell death, supporting the hypothesis that birth triggers cell death. However, a delay of birth does not delay cell death. Thus, birth can advance cell death, but if postponed, a developmental program governs. Advancing or delaying birth also caused region-specific changes in the overall magnitude of cell death. Our findings shed light on the long-standing question of what controls the timing and magnitude of developmental neuronal cell death, and position birth as an orchestrator of brain development. Because humans across the world now routinely alter birth timing, these findings may have implications for current obstetric practices.

Cerebral disorders in the first 7 years of life in children born post-term: a cohort study

Background

To estimate the association between post-term delivery and risk of physical disabilities, mental disabilities, and seizures during the first 7 years of life.

Methods

Data from 57,884 singleton infants born alive in week 39–45 by mothers included in the Danish National Birth Cohort (1997 to 2004) were analyzed, of these 51,268 were born at term (39–41 + 6) and 6616 post-term (42 + 0–44 + 6). Information on clinical endpoints was obtained from an interview at 18 months of gestational age, from a 7-year questionnaire, and from the Danish National Patient Register.

Logistic regression and Cox regression were used to estimate odds ratios and hazard rate ratios for the outcome obtained from the interview/questionnaire data and from the register-based data, respectively.

Results

We found no statistically significant increased risk of physical disabilities, mental disabilities, and epilepsy among children born post-term, though for most outcomes studied a tendency towards more adverse outcomes was seen. When children born late term (week 41) were compared to children born in week 42 or later the same tendency was found.

Conclusion

Post-term born children had a tendency to an excess risk of neurological disabilities as followed for up to 7 years of age.

Early-life social and health determinants of adult socioeconomic position: associations and trends across generations

Background

Social and biological circumstances at birth are established predictors of adult socioeconomic position (SEP). This study aims to assess the trends in these associations across two generations and examine the effects of parental early-life characteristics on descendants’ adult SEP.

Methods

We studied men and women born in the Uppsala University Hospital 1915–1929 (G1) and their offspring born 1932–1960 (G2). Data were collected in archives and routine registers. Adult SEP was assessed as an aggregate measure combining education and occupation. The exposures were family SEP, mother’s marital status, mother’s parity, mother’s age, standardised birth weight, gestational length and birth multiplicity. Linear regression was used to examine the associations across generations.

Results

The difference in adult SEP between low and high family SEP at birth was 15.8 (95% CI: 13.3 to 18.3) percentage points smaller in G2 compared with G1, although a considerable difference was still evident in G2. The associations of adult SEP with small birth weight for gestational age, post-term birth and high parity were stable between the generations: the generational differences in adjusted coefficients were 1.5 (95% CI: −1.1 to 4.1), 0.6 (–1.7 to 2.9) and 1.8 (–0.2 to 3.8) percentage points, respectively. The association between grandparental and grandchildren’s SEPs was largely explained by parental socioeconomic conditions. Father’s preterm birth was independently associated with offspring’s SEP.

Conclusion

The stability of the associations between early-life biological disadvantages and adult SEP and the persistent, although attenuated, association between early-life and adult SEPs necessitates increased policy attention to both social and health conditions at birth.

Gestational Age and Socioeconomic Achievements in Young Adulthood: A Danish Population-Based Study

IMPORTANCE

The poor health outcomes associated with preterm birth are well established. However, it is less clear how small variations in gestational age, even within the term range, are associated with long-term opportunities and well-being, as measured by socioeconomic outcomes in adulthood.

OBJECTIVE

To examine the association of gestational age at birth with educational achievement, income, and primary source of income in adulthood.

DESIGN, SETTING, AND PARTICIPANTS

This Danish population-based, register-based cohort study examined all live-born singletons born in Denmark from 1982 to 1986 without congenital anomalies and who lived in Denmark at age 28 years. Data analysis was conducted from November 2, 2017, to June 15, 2018.

EXPOSURES

Gestational age at birth in completed weeks (22-45 weeks).

MAIN OUTCOMES AND MEASURES

Educational attainment, personal income, and primary source of income at age 28 years.

RESULTS

In a population of 228 030 singletons (4.0% preterm, 12.1% early term; 49.4% female), 36.3% had a tertiary education at age 28 years. Among adults born at 22 to 27 weeks of gestation, 21.6% had a tertiary education, and 23.2% had an income in the highest tertile. Using 40 weeks of gestation as the reference, the adjusted odds ratio for tertiary education for individuals born at 22 to 27 weeks of gestation was 0.21 (95% CI, 0.13-0.35) and the corresponding figures for 28 to 31, 33, 36, 38, and 43 to 45 weeks of gestation were 0.45 (95% CI, 0.37-0.55), 0.67 (95% CI, 0.54-0.83), 0.84 (95% CI, 0.77-0.93), 0.85 (95% CI, 0.81-0.89), and 0.93 (95% CI, 0.83-1.04), respectively. The adjusted odds ratio for highest income tertile for individuals born at 22 to 27 weeks of gestation was 0.66 (95% CI, 0.41-1.06) and the corresponding figures for 28 to 31, 33, 36, 38, and 43 to 45 weeks of gestation were 0.80 (95% CI, 0.68-0.94), 0.77 (95% CI, 0.63-0.93), 0.89 (95% CI, 0.82-0.96), 0.95 (95% CI, 0.91-0.99), and 1.00 (95% CI, 0.91-1.12), respectively. All estimates were adjusted for sex, birth year, parity, maternal age, maternal education, and maternal country of origin.

CONCLUSIONS AND RELEVANCE

Shorter gestational duration even within the term range was associated with poorer socioeconomic outcomes in adulthood. While adults born at 35 to 38 weeks of gestation experienced only slightly increased risk of adverse socioeconomic outcomes, this may have a significant impact on public health, since a large proportion of all children are born in these weeks.

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.

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.