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PaediatricJan 24, 2024

Children born moderately or late preterm have higher risks of adverse neurodevelopmental outcomes

Researchers have found that children who have been. classified as ‘moderately or late preterm’ at birth have relatively high rates of neurodevelopmental difficulties when they are older, according to a study in The BMJ today (25 January).

The findings could help healthcare professionals – presumably including paediatric physiotherapists – and families to achieve better risk assessments and follow-up programmes for these groups of children, the authors suggest.

Written by an international seven-person team, the paper’s first author as Ayoub Mitha, who is based at the division of clinical epidemiology in the Department of Medicine Solna at the Karolinska Institute in Stockholm.

Previous studies showed that children who are born early have higher risks of neurodevelopmental and behavioural disabilities from the first years of life and throughout childhood and adolescence when compared with those born at term. This paper is based on one of a small number of large population-based studies to have investigated the long-term neurodevelopmental outcomes of these children compared with children born at term.

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The study sheds more light on the long-term developmental risks of being born preterm

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Researchers studied more than one million children

Dr Mitha and colleagues used Swedish national registry data to assess the long-term neurodevelopmental outcomes of children born at different gestational ages – particularly 32-33 weeks (moderately preterm) and 34-36 weeks (late preterm) – compared with 39-40 weeks (full term).

Their findings are based on 1,281,690 singleton children without birth defects born in Sweden at 32 to 41 weeks from 1998-2012 and a sub-group of 349,108 full siblings to control for unmeasured shared genetic and environmental factors

Dr Mitha and his colleagues note: ‘Children born moderately or late preterm have higher risks of adverse neurodevelopmental outcomes. The risks should not be underestimated as these children comprise the largest proportion of children born preterm.’ They add: ‘The findings may help professionals and families to better assess risk, follow-up, and healthcare systems planning for children born moderately or late preterm.’

The main outcomes of interest were movement (motor), brain (cognitive), epileptic, hearing, and visual impairments, and a combination of any neurodevelopmental impairment, diagnosed up to the age of 16. 

Potentially influential factors were taken into account including mother’s age, parity, country of birth, cohabiting status, body mass index during early pregnancy, smoking during pregnancy, diabetic and hypertensive diseases, calendar period of delivery, parents’ educational level and history of neurological and psychiatric disorders, and infant’s sex and birth weight for gestational age.

Children born moderately or late preterm have higher risks of adverse neurodevelopmental outcomes ... the findings may help professionals and families to better assess risk [and] follow-up ... [Ayoub Mitha et al]

Key findings

During an average follow-up period of 13 years, 75,311 infants (48 per 10,000 person years) had at least one diagnosis of any neurodevelopmental impairment.

Some 5,899 (4 per 10,000 person years) had motor impairment, 27,371 (17 per 10,000) cognitive impairment, 11,870 (7 per 10,000) epileptic impairment, 19,700 (12 per 10,000) visual impairment, and 20,393 (13 per 10,000) hearing impairment. 

Overall, compared with children born full term, those born moderately or late preterm showed higher risks for any impairment (e.g., an additional 475 cases per 10,000 population by age 16 years for children born moderately preterm compared with those born full term).

The highest relative risk for children born moderately preterm compared with those born full term was for motor impairment (a nearly five-fold increased risk), followed by epileptic impairment (a nearly two-fold increased risk).

Risks for neurodevelopmental impairments appeared highest from 32 weeks, then gradually declined until 41 weeks, with higher risks also at early term (37-38 weeks) than at full term. In the sibling comparison analysis, most associations remained stable except for gestational age and epileptic and hearing impairments, where no association was found. 

Study limitations

As this study was observational in nature, it cannot establish cause and the researchers acknowledge that they were unable to provide precise information for some outcomes, and that possible under-reporting or misclassification of the diagnoses might lead to an underestimation of the associations found. What’s more, they can’t rule out the possibility that other unmeasured factors – such as alcohol and substance misuse during pregnancy – could have influenced the results. 

However, this was a large, population-based study using high quality comprehensive national registries, making it possible to investigate clinically relevant risks across the spectrum of gestational age. 

To access the full version of the article – titled Neurological development in children born moderately or late preterm: national cohort study doi: 10.1136/bmj-2023-075630 – click 

Author: I A McMillan
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