Condition category
Nutritional, Metabolic, Endocrine
Date applied
Date assigned
Last edited
Retrospectively registered
Overall trial status
Recruitment status
No longer recruiting

Plain English Summary

Background and study aims
The World Health organisation (WHO) recommends that all infants should be exclusively breastfed for 6 months before starting solid foods (weaning). The quality of the research on which this recommendation is based is poor, particularly for developed countries. This is an important topic because the timing of weaning might affect a number of health outcomes in the baby such as the risk of anemia (low blood cell count, low hemoglobin) and allergy. The aims of this study is to test whether mothers who are breastfeeding their healthy term baby will agree to be randomly allocated to exclusively breast-fed their baby for 4 or 6 months, and to test whether being exclusively breast-fed for either 4 or 6 months affects how much breast-milk the infant drinks at 6 months, the infant's growth pattern or the likelihood of the infant getting low iron stores and anaemia.

Who can participate?
Infants living in the areas served by 7 health clinics in Iceland can take part in the study if they are born at term (37 weeks or more), are healthy, and are exclusively breast-fed at the age of 4 months.

What does the study involve?
The study compared infants who were exclusively breast-fed for 6 months with those who were exclusively breast-fed for 4 months who then started solid foods together with continued breastfeeding.

What are the possible benefits and risks of participating?
No side effects are expected as a result of participation in the study. There are no particular benefits to the infant from taking part in the study, although mothers will get extra breastfeeding advice if they need it, and the infant will be checked for anaemia at the age of 6 months and could be treated if a problem is found.

Where is the study run from?
The study took place in 4 health centres in Iceland (2 in Reykjavik; 1 in Akranes; 1 in Hafnarfjordur)

When is the study starting and how long is it expected to run for?
The study recruited infants from November 2007 to November 2009, with 6 month follow-up finished in May 2010.

Who is funding the study?
Mead Johnson Nutritionals and Eimskip Fund of the University of Iceland.

Who is the main contact?
Dr Mary Fewtrell

Trial website

Contact information



Primary contact

Prof Ronald Kleinman


Contact details

Physician in Chief
MassGeneral Hospital for Children
Department of Pediatrics
Pediatric Gastrointestinal and Nutrition Unit
Massachusetts General Hospital
Charles Wilder Professor of Pediatrics
Harvard Medical School
CPZS 578
175 Cambridge Street
MA 02114
United States of America

Additional identifiers

EudraCT number number

Protocol/serial number

2006-P-001453/1; MGH

Study information

Scientific title

Breastfeeding and child health: randomized controlled trial on the impact of age of introduction of weaning foods



Study hypothesis

1. It is feasible to randomise mothers to exclusively breast-feed for 4 or 6 months
2. The duration of exclusive breastfeeding and the age at introduction of complementary (weaning) foods will affect infant breast-milk intake, infant growth and infant iron status at age 6 months.

Ethics approval

1. Data Protection Authority and National Bioethical Committee in Iceland approved on 04/27/2007 ref: 02-164-V3-S1
2. Partners Health System IRB (US) approved on 10/25/2007, ref: 2006-P-001453/1

Study design

Parallel-group masked randomized controlled trial

Primary study design


Secondary study design

Randomised controlled trial

Trial setting

GP practices

Trial type


Patient information sheet

Not available in web format, please use the contact details below to request a patient information sheet


Healthy term infant feeding


Exclusive breastfeeding for 6 months compared to exclsuive breastfeeding to 4 months with introduction of solid foods alongside continued breastfeeding.

Intervention type



Drug names

Primary outcome measures

1. Feasibility
1.1 Proportion of mothers that will breastfeed exclusively for 6 months
1.2 Proportion of mothers randomized at 4 months (from those invited to participate)
2. Measurements at 6 months
2.1 Infant breast milk intake (by stable isotopes)
2.2 Infant growth
2.3 Infant iron status

Secondary outcome measures

1. Infant food intake
2. Infant body composition
3. Occurrence of upper respiratory infections and diarrheal episodes (dichotomous variables)

Overall trial start date


Overall trial end date


Reason abandoned


Participant inclusion criteria

1. Healthy term infant (>37 weeks gestation)
2. No health issues affecting growth
3. No other siblings enrolled in the study
4. Exclusively breast-fed at age 4 months

Participant type


Age group




Target number of participants

100 infants completing study to 6 months, from 7 healthcare centers

Participant exclusion criteria

Infant not exclusively breast-fed at age 4 months

Recruitment start date


Recruitment end date



Countries of recruitment


Trial participating centre

Massachusetts General Hospital
MA 02114
United States of America

Sponsor information


Mead Johnson Nutritionals (USA)

Sponsor details

c/o - Chelsea Hunter / Tim Cooper
2400 West Lloyd Expressway B201
United States of America

Sponsor type




Funder type


Funder name

Mead Johnson Nutrition

Alternative name(s)

Mead Johnson

Funding Body Type

private sector organisation

Funding Body Subtype



United States of America

Funder name

Eimskip Fund of the University of Iceland (Iceland)

Alternative name(s)

Funding Body Type

Funding Body Subtype


Results and Publications

Publication and dissemination plan

Not provided at time of registration

Intention to publish date

Participant level data

Not provided at time of registration

Results - basic reporting

Publication summary

2012 results in:
2014 results in:

Publication citations

  1. Results

    Jonsdottir OH, Thorsdottir I, Hibberd PL, Fewtrell MS, Wells JC, Palsson GI, Lucas A, Gunnlaugsson G, Kleinman RE, Timing of the introduction of complementary foods in infancy: a randomized controlled trial., Pediatrics, 2012, 130, 6, 1038-1045, doi: 10.1542/peds.2011-3838.

  2. Results

    Jonsdottir OH, Fewtrell MS, Gunnlaugsson G, Kleinman RE, Hibberd PL, Jonsdottir JM, Eiriksdottir I, Rognvaldsdottir AM, Thorsdottir I, Initiation of complementary feeding and duration of total breastfeeding: unlimited access to lactation consultants versus routine care at the well-baby clinics, Breastfeed Med, 2014, 9, 4, 196-202, doi: 10.1089/bfm.2013.0094.

Additional files

Editorial Notes