While previous studies have shown that children born early have higher risks of neurodevelopmental and behavioural disabilities throughout childhood and adolescence compared with children born at full term, few population-based studies have investigated the long term neurodevelopmental outcomes of these children, the researchers said
Children born prematurely have been associated with higher risks of having adverse neurodevelopmental outcomes, which can affect their behaviour and learning abilities, according to a study of over a million children.
Researchers compared the long term neurodevelopmental effects 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).
The team of researchers, including those at Karolinska Institutet, Sweden, found that the highest relative risk for moderately preterm-born children was for motor impairment (nearly five-fold increased risk), followed by epileptic impairment (nearly two-fold increased risk), compared to full term-born children.
While motor impairment refers to a physical disability and could result in muscle weakness, poor stamina, reduced balance, or poor co-ordination, epileptic impairment pertains to a disorder of the central nervous system.
They also found that the highest level of risks for neurodevelopmental impairments appeared from 32 weeks and then gradually declined until 41 weeks, with higher risks present even at 37-38 weeks than at full term. Their findings are published in The British Medical Journal (BMJ).
While previous studies have shown that children born early have higher risks of neurodevelopmental and behavioural disabilities throughout childhood and adolescence compared with children born at full term, few population-based studies have investigated the long term neurodevelopmental outcomes of these children, the researchers said.
As the children they studied comprise about 80 per cent of all preterm births, these neurodevelopmental risks should not be underestimated, they said.
For the study, the researchers used the Swedish national registry to include more than 12.5 lakh single-born children without birth defects born in Sweden at 32 to 41 weeks between 1998 and 2012.
Over an average follow-up period of 13 years, the team found that more than 75,000 infants had at least one diagnosis of any neurodevelopmental impairment, with those born moderately or late preterm showing higher risks for any impairment.
Nearly 5,900 infants had motor impairment, more than 27,000 had cognitive impairment, 11,870 had epileptic impairment, 19,700 had visual impairment and about 20,400 had hearing impairment, they found.
Being an observational study, the researchers said they could not establish a causal relationship and also acknowledged that possible under-reporting or misclassification of the diagnoses might result in underestimating the associations found.
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, they said.
”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,” the team wrote in their study.
”The findings may help professionals and families to better assess risk, follow-up, and healthcare systems planning for children born moderately or late preterm,” they wrote.