Background and Aims To describe maternal perceptions of their child’s BMI and maternal report of concerns about body weight raised by a health professional.

Methods Data collection took place in 2010 when children were between 6 and 8 years of age and questionnaires were mailed to 706 mothers who were part of a longitudinal cohort that had been followed since pregnancy. Mothers reported the child’s anthropometric measures, and BMI was categorized as underweight, healthy, overweight, or obese based on the child’s age and sex according to the World Health Organization Growth Charts adapted for Canada.

Results 450 participants completed the questionnaire (response rate 64%). 74% of children had a healthy BMI, 10% were underweight, 9% were overweight, and 7% were obese. 80% of parents whose child was underweight believed their child was about the right weight and only 13% recalled a health professional recently raising concerns about their child being underweight. 89% of parents whose child was overweight believed their child was about the right weight and only 6% recalled a health professional recently raising concerns about their child being overweight. 62% of parents whose children were obese believed their child was about the right weight and only 18% recalled a health professional recently raising concerns about their child being overweight.

Conclusions The majority of parents whose children were not a healthy BMI misclassified their child’s weight status, suggesting that there are opportunities for health professionals to educate parents about healthy BMI for their child’s age and sex.