Bigger babies likely to end up being more intelligent, new research suggests

Bigger babies are likely to be more intelligent than their lighter counterparts, a new study has claimed.

New research published today in JAMA Network Open suggests that there is a connection between pregnancy length, birthweight and cognitive development.

The study, led by Bielefeld University and the University of Warwick, combined data from around the world, based on four large international infant cohorts of over 30,000 children.

Researchers found that a large birthweight is good for IQ, but this is relative to gestational age (the week of pregnancy the baby is born – for a healthy nine-month pregnancy this is 40 weeks).

By contrast, babies with a lower birthweight are more likely to experience developmental problems later by the age of five.

Lead author Robert Eaves said: "When a baby is born their birthweight percentile is often calculated, which is their birthweight relative to their gestational age. Traditionally, researchers have used above or below the 10th percentile as a potential risk factor for long-term developmental issues.

"We find no evidence that there is anything particularly unique about the 10th percentile. We find that increasing birthweight percentiles are associated with increased cognitive scores, from the first percentile until the 69th percentile.

"It’s also important to note that while relative birthweight and gestational age may influence childhood development, they are two of potentially many other factors, such as the parent-child relationship, that also help to shape the development of the child.”

Professor Dieter Wolke from the University of Warwick added: "Obstetricians have to balance decisions due to potential complications for foetus or mother against potential trade-offs of early delivery on child cognitive outcome. Our results help in the decision process as the analysis considers both gestation and birth weight.

"It shows that risk for cognitive sequelae is highest when gestation and birthweight are low but suggests that if the anticipated birthweight is high being born a week or three earlier may have little adverse impact on cognitive outcome by five years.”