Heavier newborns perform better academically in elementary and middle school than peers with lower birth weights, according to a new study by researchers at Northwestern University in Evanston, IL.
Previous research has found that low birth weight is associated with a variety of adverse outcomes in later childhood.
Studies reported on by Medical News Today have suggested that low-birth-weight babies are more likely to have autism spectrum disorder, psychiatric problems and childhood illness or lower promotion prospects in later life.
The new study, published in the journal American Economic Review, is the first to explore the interaction between birth weight, children’s cognitive development and the quality of education they have.
The researchers used merged birth and school records for all children born in Florida during the period 1992-2002, which included more than 1.3 million children and nearly 15,000 pairs of twins.
The study finds that babies who weigh more at birth score more highly on tests from third to eighth grade. This finding was confirmed in the participants who were twins; twins with a heavier birth weight go on to have higher average test scores than siblings with lower birth weights.
Perhaps surprisingly, when the researchers took into account the quality of the schools the participants were attending, they found that birth weight was still a more influential factor on academic outcome than school quality.
Being born a heavier weight was found to be advantageous for all children, say the researchers, regardless of race, socioeconomic status and a variety of other factors.
“The results strongly point to the notion that the effects of poor neonatal health on adult outcomes are largely determined early – in early childhood and the first years of elementary school,” the authors write in their conclusion.
However, this does not mean that children born with a low weight are unable to perform better than heavier peers academically.
On the influence of maternal education, study coauthor Jonathan Guryan, an associate professor of human development and social policy at the School of Education and Social Policy, says: “You’d rather be a low-birth-weight baby with a mother who has a college degree than a heavier baby born to a high school dropout.”
The researchers say their findings support the theory that a fetus benefits from a longer stay in the mother’s womb.
David Figlio, one of the study’s authors and director of Northwestern’s Institute for Policy Research, explains:
“A child who is born healthy doesn’t necessarily have a fully formed brain. Our study speaks to the idea that longer gestation and accompanying weight gain is good. We want to know: what does that mean for public policy?”
Other recent research investigating low-birth-weight children has found that they are more vulnerable to environmental influences than infants born at a normal weight.
A study in the Journal of Child Psychology and Psychiatry reported that low-birth-weight children – when brought up “with a great deal of sensitivity” – can catch up in school with their peers, but they will not, on average, become better students than normal-birth-weight children.