Smaller babies perform poorer as teens, study finds

Babies who are smaller than expected at birth tend to have poorer school performances as teenagers, a study has found.

More than 92,000 children were followed from infancy to adolescence, all of whom were born at full term, between 37 and 41 weeks pregnant.

The researchers at the University of Warwick found that children who weighed less than most babies of the same sex, born at the same stage of pregnancy, tended to achieve lower scores in subjects like mathematics and reading.

The differences were still apparent in adolescence, suggesting that the link between size at birth and academic performance persists well beyond early childhood into mid-teens.

"For babies born at term, being small for their stage of pregnancy may indicate adverse effects on the brain that affect learning and last into adolescence," Prof Dieter Wolke said.

However, he said the long-term effects of being born small may be altered by parenting home stimulation and school support.

His colleague Prof Siobhan Quenby said not every baby born smaller than expected would experience difficulties, but the study's results underlined the importance of "monitoring a baby's growth and ensuring that children receive appropriate support as they develop".

Researchers also looked at those born at 37 to 38 weeks of pregnancy and found that those children tended to have slightly poorer language and movement skills in early childhood than those born later, but the differences had become minimal by the time they started school.

They examined children's language and motor skills at about six months, 18 months, three years and five years of age.

"This study is important because we now know that if your baby is normal size or large for its stage in pregnancy there are no long-term effects of being delivered a few weeks before your due date," Quenby said.

The study was led by researchers from the University of Warwick and the PsychGen Centre at the Norwegian Institute of Public Health, working with other collaborating institutions in Norway.

In all, 92,551 children based in Norway were followed.

Results from national school tests in maths, reading and English, including tests taken at about 10-11, 13-14 and 14-15 years of age were also analysed.

The findings were published in the American Journal of Obstetrics and Gynecology.

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