Higher Risk of Long-term Neurodevelopmental Issues in Preterm Babies

Children born moderately (32-33 weeks) or late preterm (34-36 weeks) have a higher long-term risk of neurodevelopmental issues that might influence their behavior and capacity to learn, according to a study of over one million children published today in The BMJ.

These dangers should not be underestimated, as these youngsters account for around 80% of all preterm deliveries, according to the researchers. The findings may also assist professionals and families in better risk assessment and monitoring of these children.

Previous research has shown that children born early are more likely to suffer neurodevelopmental and behavioral impairments in their initial years of life, as well as throughout childhood and adolescence, than those born at term. However, few population-based studies have looked at how these children’s long-term neurodevelopmental results compare to those of term-born children.

To bridge this knowledge gap, researchers used Swedish national registry data to evaluate the long-term neurodevelopmental outcomes of children born at various gestational ages, specifically 32-33 weeks (moderately preterm) and 34-36 weeks (late preterm), to 39-40 weeks (full term).

Their findings are based on 1,281,690 singleton children without birth abnormalities born in Sweden at 32 to 41 weeks between 1998 and 2012, as well as a subset of 349,108 complete siblings to account for unmeasured shared genetic and environmental variables.

The most common outcomes of interest were movement (motor), brain (cognitive), epileptic, hearing, and visual impairments, as well as a combination of any neurodevelopmental issues detected before the age of 16.

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 were all considered potential influences.

During an average follow-up duration of 13 years, 75,311 babies (48 per 10,000 person years) received at least one diagnosis of neurodevelopmental issues.

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

Overall, children born moderately or late preterm had a greater chance of any impairment than those born full term.

The biggest 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 deficits were highest at 32 weeks and steadily decreased until 41 weeks, with larger risks at early term (37-38 weeks) than at full term.

The majority of relationships were consistent in the sibling comparison study, with the exception of gestational age, epilepsy and hearing abnormalities, which showed no association.

This is an observational study, thus cause cannot be established, and the researchers recognize that they were unable to offer accurate information for some outcomes, and that possible under-reporting or misclassification of diagnoses may have resulted in an underestimating of the connections reported.

Furthermore, they cannot rule out the possibility that other unmeasured variables, such as alcohol and substance abuse during pregnancy, influenced the results.

However, this was a big, population-based study that used high-quality comprehensive national registries, allowing researchers to evaluate clinically relevant hazards across the gestational age range.

As such, they state that “children born moderately or late preterm have a higher risk of unfavorable neurodevelopmental outcomes. The hazards should not be underestimated, as these children account for the majority of premature births.

“The findings may help professionals and families to better assess risk, follow-up, and healthcare systems planning for children born moderately or late preterm,” according to the researchers.

For more information: Neurological development in children born moderately or late preterm: national cohort study, BMJ, https://doi.org/10.1136/bmj-2023-075630