Body mass index and duration of breast feeding: a survival analysis during the first six months of life.

STUDY OBJECTIVE The aim was to determine whether excess weight in lactating women is associated with earlier cessation of breastfeeding. DESIGN The study was to prospective cohort analysis using a community sample of women. SETTING Geelong the regional centre of the Barwon Region of Victoria, Australia, in 1984-85. SUBJECTS All women who were breast feeding and whose first infant was born between 1 May 1984 and 30 April 1985 were asked to participate. Of these, 739 women participated, a response rate of 81%. MAIN RESULTS Smoking, mother's age and occupation, the time the infant was first put to the breast, and mother's body mass index at one month postpartum all exerted statistically significant independent effects on the duration of breast feeding, assessed using Cox's proportional hazards regression modelling. The strongest effects were for smoking, with an adjusted relative risk for cessation of breast feeding of 2.5 (95% CI 1.9 to 3.1) for 10 cigarettes per day v no smoking, and maternal age, with relative risk of 2.2 (95% CI 1.5 to 3.1) for a 20 year old mother relative to a 30 year old. The relative risk for women with a body mass index above 26 was 1.5 (95% CI 1.1 to 2.0). CONCLUSIONS Excess weight at one month postpartum, as determined by a body mass index above the normal range, was found to be an independent risk factor for early cessation of breast feeding and together with smoking, maternal age, occupation, and the time the infant is first put to the breast can be used to identify, early in the postpartum period, those women most likely to benefit from counselling in order to breast feed their infants successfully.