Preterm birth linked to lower school grades during adolescence

A large Danish population-based study found that preterm birth before 34 weeks of gestation was associated with lower scores in math and language tests in adolescents compared to those born at 40 weeks.

However, a study published in BMJ found no significant difference in late brain cognition between children born at 34–39 weeks of age and children born at 40 weeks of age.

Researchers recognize that cognitive outcomes are not only predetermined at birth, but are also highly dependent on social conditions.

It is estimated that around 15 million babies are born prematurely before 37 weeks of gestation worldwide each year. The last weeks of pregnancy are important for fetal brain development, and preterm birth is thought to have a negative impact on later brain function.

However, previous studies were relatively small, limited mostly to one dimension, or did not adequately account for other factors that may have influenced the results.

To more accurately determine the effect of gestational age (gestational age in weeks) at birth on long-term cognitive function, the researchers analyzed data from all siblings born in Denmark between January 1, 1986 and December 31, 2003.

A total of 1.2 million babies were born during this period, of which 792,724 had at least one sibling, allowing researchers to take into account genetic factors such as the mother’s intelligence.

Using national enrollment information, the researchers analyzed gestational age at birth as well as their written Danish language and math scores at ages 15-16, as well as separately scores on intelligence tests taken by 227,403 siblings around the age of 18. in the call.

The analysis also took into account potential confounding factors, including gender, birth weight, parental age, education level at birth, number of older siblings, and family factors shared by siblings.

The researchers calculated how much above or below average the test score was and compared that score for siblings at each gestational age with the score for full-term siblings in the class.

Overall, 44,322 (5.6%) of 792,724 babies were born before 37 weeks. Of these, only those born before 34 weeks had math scores that were significantly below average than those born at 40 weeks, and scores progressively declined as prematurity increased.

In terms of written language, children born at 27 weeks of age or less showed significantly lower scores than average.

An analysis of military recruitment intelligence test scores, measured in IQ scores, also showed significantly lower test scores for those born before 34 weeks.

And those born after 34 weeks saw a drop in IQ of less than one point compared to those born after 40 weeks. But there was a 2.4-point IQ drop for those born between 32-33 weeks, a 3.8-point drop for 28-31 weeks, and a 4.2-point drop for those born before or before 27 weeks.

This is an observational study, so a cause cannot be determined, and the researchers also acknowledge some limitations. For example, smoking during pregnancy was not reported until 1991 and test results may differ from actual results such as lifetime income.

But they say the study has the benefit of a large sample size and that the design of the sibling comparison likely explains other factors, such as the mother’s smoking. The results also appeared to be similar after further analysis, such as including children who failed exams, suggesting that the results stand up to scrutiny.

While the reasons for these results remain unclear, the researchers note that because cognitive decline is associated with reduced quality of life and early death, their results “highlight the need for further research on how to prevent these negative effects.”

Source: Medical Express