Babies breastfed or bottle-fed to a schedule may not perform as well in school as babies fed on demand, British researchers found.

Study leader Dr. Maria Iacovou of the Institute for Social and Economic Research at University of Essex and at the University of Oxford said this was the first ever large-scale study to investigate the long-term outcomes of schedule versus demand-fed babies.

The study, published in the European Journal of Public Health, found demand-feeding was associated with higher IQ scores at age 8, and higher school scores at ages 5, 7, 11 and 14.

Scheduled feeding times did have benefits for mothers, who reported feelings of confidence and high levels of well-being, Iacovou said.

"The difference between schedule and demand-fed children is found both in breastfed and in bottle-fed babies," Iacovou said in a statement.

"The difference in IQ levels of around 4 to 5 points, though statistically highly significant, would not make a child at the bottom of the class move to the top, but it would be noticeable.

To give a sense of the kind of difference of the increase, in a class of 30 children, a child who is right in the middle of the class, ranked at 15th, might be, with an improvement of 4 or 5 IQ points, ranked higher, at about 11th or 12th in the class."