Premature birth affects performance on language, math and IQ tests

Premature infants born at less than 34 weeks of gestation perform worse on intelligence and math tests. And those born at less than 27 weeks also have worse results in language, according to research published in the scientific journal The British Medical Journal, one of the most respected in the field of health.

Conducted by researchers from institutions in England, Denmark, Norway and the United States, the study had as its starting point data from 1,161,406 births registered in Denmark between January 1, 1986 and December 31, 2003.

The scientists identified how many of these children had siblings (792,724) and, within that group, how many were born before 37 weeks of gestation (44,322). Babies younger than 37 weeks are classified as premature, and those born at less than 28 weeks are classified as extremely premature.

By considering only individuals with siblings, the research minimized the influence of family factors, as the children grew up in the same environment. The researchers also took care to adjust for variables such as gender, birth weight, parents’ age at birth, and parents’ education.

They then assessed the scores of those born prematurely on written language (Danish) and math tests administered across Denmark in the ninth grade, when students are between 15 and 16 years old. In the case of male adolescents, they also found differences in the intelligence test applied in the process of compulsory military enlistment, at 18 years old.

The group found that children born at 27 weeks or less have a reduced average in language and that performance in mathematics and on the IQ (intelligence quotient) test drops considerably among those younger than 34 weeks.

On the IQ test, babies born less than 27 weeks lost 4.2 points; between 28 and 31 weeks, the reduction was 3.8 points; between 32 and 33, 2.4 points; and, from 34 weeks, reduction of 1 point.

“Cognitive outcomes in adolescence did not differ between those born at 34 to 39 weeks of gestation and those born at 40 weeks of gestation, while those born at less than 34 weeks of gestation showed substantial deficits in multiple cognitive domains”, the authors ponder.

The article also points out the reduction in the performance of children born at 42 weeks or more, but explains that more research focusing on this group is needed to confirm the drop.

For Licia Maria Oliveira Moreira, president of the Scientific Department of Neonatology at the SBP (Brazilian Society of Pediatrics), the study has several highlights. In addition to methodological precautions when considering children with siblings, it evaluates adolescents, while previous studies observe performance in childhood. With this, it is possible to better understand the consequences of prematurity in another stage of life.

“In the whole world, we are living with the lowest mortality, including extremely premature infants, and as we reduce mortality, we increase the number of children who will become adolescents and adults with these complications. Prematurity has a social, economic and emotional impact not only in the period after birth, but throughout life”, says Moreira.

In Brazil, around 2.7 million children are born each year, and the prematurity rate is still much higher than in Denmark — here it is 10%, with some places reaching 12%, according to the SBP.

“The great message of the research is to reinforce the importance of preventing prematurity and, once it occurs, try to provide the best possible support for the child to have quality of life”, evaluates the neonatologist.

Such support includes nutrition, vaccination and constant stimulation, guided by specialized professionals, such as speech therapists and neuropediatricians. “Children who are born at 34 weeks or more, if they are not stimulated, may also have lower performance”, she points out.

Another relevant point of the research, says Moreira, is to present more evidence of the damage caused by extreme prematurity. “The brain of a baby at 25, 27 weeks is still all smooth. In the following weeks, he grows and creates skills, and his neurotransmitters develop. Each week, each day of gestation makes an incredible difference.”