New research suggests that Kate Middleton's baby will become more intelligent the longer she continues to breastfeed him.

The Duchess of Cambridge, who is reportedly breastfeeding her newborn baby George, may be interested in a study by the journal JAMA Pediatrics, which claims the length of time a child is breastfed is directly related to its intelligence later in life.

The study suggests that longer breastfeeding enables better receptive language at three years of age and enhanced verbal and non-verbal intelligence at seven. However, evidence of the extent to which breastfeeding helps in a child's development after infancy is less certain.

"In summary, our results support a causal relationship of breastfeeding in infancy with receptive language at age 3 and with verbal and non-verbal IQ at school-age. These findings support national and international recommendations to promote exclusive breastfeeding through to the age of 6 months and continuation of breastfeeding through at least age 1 year," the authors of the report noted.

"Breastfeeding an infant for the first year of life would be expected to increase his or her IQ by about four points or one-third of a standard deviation," Dimitri A. Christakis, a member of the research team added.