Preterm Birth Pushes Down School Grades in Adolescence

A total of 1.2 million children were born in this period, of whom 792,724 had at least one full sibling born in the same period, which allowed the researchers to take into account hereditary factors such as maternal intelligence.

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Later, they analyzed gestational age at birth, along with their exam results in written Danish language and maths at age 15-16 years, and separately, the results of intelligence tests taken by 227,403 brothers aged around 18, at mandatory military conscription.

Potentially influential factors, including sex, birth weight, parental age and educational level at birth, number of older siblings, and shared family factors between siblings were also taken into account in the analysis.

The researchers calculated how far an exam result was above or below the average grade, and compared this score for siblings at each gestational age to the score for siblings born at term.

Being Born Early Might Affect a Child’s Progress at School

Overall, 44,322 (5.6%) of the 792,724 children were born before 37 weeks. Of these, only those born before 34 weeks had significantly lower than average maths scores than those born at 40 weeks, and grades progressively decreased with increasing prematurity.

For written language, however, only children born at or less than 27 weeks showed a significantly lower-than-average grade. Analysis of military conscription intelligence test scores, measured in IQ points, also showed markedly lower test scores for those born before 34 weeks.

For those born after 34 weeks, there was a less than 1 point reduction in IQ, compared with those born at 40 weeks. But there was a 2.4 point IQ reduction for those born between 32 and 33 weeks, a 3.8 point reduction for those born between 28 and 31 weeks, and a 4.2 point reduction for those born at or before 27 weeks.

This is an observational study, so it can’t establish cause, and the researchers also acknowledge some limitations. For instance, smoking during pregnancy was not recorded before 1991, and test results may differ from real-life outcomes such as lifetime income.

While the underlying reasons for these findings are still not clear, the researchers suggest that as low cognitive ability is linked to decreased quality of life and early death. Their findings stress the need for more research to prevent these adverse outcomes.

However, parents and clinicians should be aware of potential educational and cognitive difficulties associated with preterm birth. Since the causes of preterm birth are complex and poorly understood, efforts to identify and improve on other socio-environmental factors could be a more successful approach.

Source: Eurekalert