Prevalence of breast milk expression and associated factors.

Objectives: Our goal was to describe the prevalence of any, occasional, and regular breast milk expression, mothers' reasons for expressing their milk, and sociodemographic factors associated with breast milk expression.

Participants And Methods: Breastfeeding mothers participating in the 2005-2007 Infant Feeding Practices Study II formed the cohort for these analyses, which were conducted among those with infants in 3 age groups: 1.5 to 4.5 months (n = 1564); >4.5 to 6.5 months (n = 1128); and >6.5 to 9.5 months (n = 914). For the analyses we used frequency and stepwise multiple logistic regression procedures.

Results: Eighty-five percent of breastfeeding mothers of infants in the youngest age group had successfully expressed milk at some time since their infant was born. When asked only about the previous 2-week period, 68% of the breastfeeding mothers of infants in this youngest age group had expressed milk, with 43% having done so occasionally and 25% on a regular schedule. Approximately one quarter of breastfeeding mothers of infants in the 2 older infant age groups also expressed milk on a regular schedule. The percentage of mothers expressing milk decreased with increasing infant age. Mothers expressed milk for various reasons. The most frequently cited reason was to get breast milk for someone else to feed their infant. In all 3 age groups, reporting any breast milk expression, compared with none, was positively associated with maternal employment, higher income, lack of previous breastfeeding experience, and living in the Midwest versus the West. In all 3 age groups, expressing milk on a regular schedule, compared with occasionally, was positively associated with maternal employment and the use of an electric versus manual breast pump.

Conclusions: Breast milk expression is a very common practice. It is associated most strongly with maternal employment, a recognized barrier to breastfeeding.