Article Text

An intervention promoting exclusive and prolonged breast feeding improved verbal intelligence scores in children at 6.5 years

Statistics from

M S Kramer

Dr M S Kramer, Montreal Children's Hospital, Montreal, Quebec, Canada; michael.kramer{at}



cluster randomised controlled trial (Promotion of Breastfeeding Intervention Trial [PROBIT]).




blinded (teacher ratings).*



33 maternity hospitals and affiliated polyclinics in Belarus, 2 of which refused to participate after randomisation.†‡


17 046†‡ healthy breast-fed infants who were born at term, enrolled in hospital postpartum, and weighed ⩾2500 g at birth.


promotion and support of exclusive and prolonged breast feeding for mothers who had decided to breast feed (16 centres,† 7108 infants) or usual care (15 centres,† 6781 infants). The intervention was based on the Baby-Friendly Hospital Initiative (BFHI) developed by the World Health Organisation and UNICEF.


included Wechsler Abbreviated Scales of Intelligence (WASI) with full-scale, verbal (vocabulary and similarities subtests), and performance (block designs and matrices subtests) scales, and academic ratings by teachers (not reported here because <80% follow-up).

Participant follow-up:

94% of hospitals and 81% of children (52% boys) (intention-to-treat analysis).†‡

Follow-up period:

6.5 years.


Children in the intervention group performed better than those in the usual-care group on verbal intelligence tests; groups did not differ for other intelligence scores (table).

Breast feeding promotion v usual care for cognitive development of children*


An intervention to promote exclusive and prolonged breast feeding after birth improved verbal intelligence scores, but not performance or overall intelligence scores, in children at 6.5 years.

*See glossary.

Kramer MS, Chalmers B, Hodnett ED, et al. JAMA 2001;285:413–20.

‡Excluding 1 polyclinic (n = 749) that falsified outcome data.


Kramer MS, Aboud F, Mironova E, et al. Breastfeeding and child cognitive development: new evidence from a large randomized trial. Arch Gen Psychiatry 2008;65:578–84.

Clinical impact ratings: Paediatrics 7/7; GP/FP/Mental health 6/7; Psychiatry 6/7; Paediatric neonatology 6/7; Public health 5/7; Obstetrics 5/7; GP/FP/Primary care 5/7


The trial by Kramer et al is outstanding in the field of infant nutrition. The intervention was the BFHI, which included 10 steps to successful breast feeding. Cluster randomisation of maternity clinics was successful in overcoming the obvious difficulties of randomising women to breast feed or not, with 43% v 6% breast feeding exclusively at 3 months and 20% v 11% still breast feeding at 12 months. The study was conducted in Belarus, a former Soviet republic that has a population of 10 million, with educational status similar to that of most Western countries and an infant mortality rate of 6.5/1000.

This large, long-term trial provides strong evidence that breast feeding improves infants’ cognitive development. In the intention-to-treat analysis, the intervention group had higher verbal intelligence scores and trends toward higher scores in all other areas of the WASI, and in teacher ratings of academic performance. The mechanism for this benefit needs to be studied before the formula industry claims that additives can mimic benefits, and to determine the role of human milk banks in the feeding of term infants.

Duration and exclusivity of breast feeding were also associated with higher intelligence scores, although only 7.9% of the intervention group and 0.6% of the usual-care group were breast feeding exclusively at 6 months. To support the recommendation for 6 months of exclusive breast feeding, further research is needed on timing of introducing solids because delays have been associated with increased risk of allergy.1

The findings of Kramer et al are consistent with most previous studies and meta-analyses2 and lend strong support to implementation of the BFHI around the world. Future trials should focus on community interventions aimed at increasing the duration of breast feeding.


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  • Source of funding: Canadian Institutes of Health Research.

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