Study sheds more light on long-term developmental risks of preterm birth

Children born moderately premature (32 to 33 weeks) or late prematurely (34 to 36 weeks) have higher long-term risks of neurodevelopmental difficulties that can affect their behavior and ability to learn, according to a study of more than one million children. The results are published in The BMJ Today.

As these children account for around 80% of all premature births, these risks should not be underestimated, researchers say. The results can also help professionals and families to better assess risks and better monitor these children.

Previous research shows that children born early have higher risks of neurodevelopmental and behavioral disorders during the first years of life and throughout childhood and adolescence, compared to children born full-term. Yet, few population-based studies have investigated the long-term neurodevelopmental outcomes of these children compared to full-term children.

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

Their results are based on 1,281,690 singleton children without birth defects born in Sweden between 32 and 41 weeks between 1998 and 2012 and a subgroup of 349,108 full siblings to control for unmeasured shared genetic and environmental factors.

The primary outcomes of interest were motor (motor), cerebral (cognitive), epileptic, hearing, and visual impairments, as well as a combination of any neurodevelopmental impairment, diagnosed up to 16 years of age.

Potentially influential factors were considered, including maternal age, parity, country of birth, cohabiting status, body mass index at early pregnancy, smoking during pregnancy, diseases diabetics and hypertensives, the calendar period of delivery, the level of education of the parents and the history of neurological and neurological disorders. psychiatric disorders, sex and infant birth weight in relation to gestational age.

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

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

Overall, compared to children born at term, those born moderately or late preterm had higher risks of impairment (e.g., 475 additional cases per 10,000 population at age 16 for children born moderately preterm compared to those born at term).

The highest relative risk for children born moderately premature compared to those born full term was that of motor impairment (a risk almost five times higher), followed by seizure impairment (a risk almost twice as high). .

The risks of neurodevelopmental disorders appeared higher from 32 weeks onwards, then gradually decreased until 41 weeks, with higher risks also at early term (37 to 38 weeks) than at term.

In the comparative sibling analysis, most associations remained stable, with the exception of gestational age and epileptic and hearing impairment, for which no associations were found.

This is an observational study, so it cannot establish cause, and the researchers acknowledge that they were unable to provide precise information on some findings, and that possible underreporting or misclassification of diagnoses could lead to an underestimate of the associations found.

Additionally, they cannot rule out the possibility that other unmeasured factors, such as alcohol and substance abuse during pregnancy, may have influenced the results.

However, this was a large population-based study using high-quality, comprehensive national registries, allowing for the investigation of clinically relevant risks across the entire gestational age spectrum.

As such, they say, “children born moderately or shortly preterm are at higher risks of neurodevelopmental problems.” The risks should not be underestimated, as these children represent the largest proportion of children born preterm.”

“The results could help professionals and families better assess risks, follow-up and plan health systems for children born moderately or late prematurely,” they add.