A new study of pre-term babies has found that the more breast milk they have in the first 28 days of their life, the more likely they are to develop larger volumes in crucial brain regions.

Compared to pre-term babies whose initial diet included more pre-term formula, babies who consumed more breast milk also had better IQs, academic achievement, working memory, and motor function at seven years old.

"Our data support current recommendations for using mother's milk to feed pre-term babies during their neonatal intensive care unit (NICU) hospitalisation," said one of the team, Mandy Brown Belfort from the Boston Hospital & Medical Centre.

"This is not only important for mums, but also for hospitals, employers, and friends and family members, so that they can provide the support that's needed during this time when mothers are under stress and working so hard to produce milk for their babies."

Brown Belfort and her team analysed data from 180 pre-term babies born before 30 weeks gestation in the US between 2001 and 2003. Over the first 28 days after birth, they calculated how many days the infants received more than 50 percent whole breast milk as part of their nutritional intake. 

This was then correlated to certain mental and physical characteristics both at term equivalent (when the babies 'should' have been born), through to school age. 

Magnetic resonance imaging ( MRI) scans were taken at both term equivalent and seven years to calculate the increase in grey and white matter volume across all major regions of the brain.

Interestingly, they found that infants who received more breast milk ended up developing more deep nuclear grey matter - an area important for processing and transmitting neural signals across the brain - and hippocampus volume by term equivalent, but this increase in brain volume appeared to even out by age seven.

Publishing their results in The Journal of Pediatrics, the team suggests that this initial boost in brain volume could be due to the fact that the pre-term brain is more sensitive to the beneficial effects of breast milk at the very early stages of development.

Much longer-lasting effects were found on the cognitive side of things, with the team finding that at age seven, the kids' IQ was 0.5 points higher for every additional day they had more than 50 percent breast milk intake as infants, and 0.7 points higher per additional 10 mL of breast milk ingested.

They also linked higher breast milk intake to better motor function, academic achievement in reading and mathematics, working memory, language, and visual perception by the age of seven. Factors such as maternal education, family income, and maternal IQ were accounted for.

"Overall, it seems that greater exposure to breast milk is associated not only with higher general intelligence, but also with better academic achievement, memory, and motor function in children who were born very pre-term," the team reports.

So what does this mean for new mums? 

While the study is limited by the fact that it can only show a correlation between certain physical and cognitive advantages and a higher intake of breast milk, previous studies have suggested that the link could be due to the fact that specific nutrients in breast milk that are either absent from formula or are there in lower amounts. 

As suggested by this study, this could be having a real effect on the lives of pre-term babies.

Of course, until scientists can confirm that, there's no reason for mums of pre-term babies to freak out. Instead, Brown Belfort says the results show how important it is for mums to be given as much support as possible to help them increase breastfeeding frequency, because for some women, this can be anything but easy.

"Many mothers of preterm babies have difficulty providing breast milk for their babies, and we need to work hard to ensure that these mothers have the best possible support systems in place to maximise their ability to meet their own feeding goals," says Brown Belfort

"It's also important to note that there are so many factors that influence a baby's development, with breast milk being just one," she adds.